Why You Must Use a Digital Scan Head in a Laser Marking Machine

In a basic laser marking or laser engraving machine the scan head, otherwise known as the beam deflection unit or the galvo head, is a key component with regard to the performance and reliability of the system.

There are many manufacturers of these types of device with significantly variable performance characteristics but one major differential to consider is whether or not the unit is digital or analogue.

Lower cost laser marking machines tend to use analogue technology because the component cost is significantly lower. The downside to using an analogue scan head is that it is more prone to drift out of accuracy especially if the unit is worked hard and builds-up a significant degree of retained heat (thermal drift).

Over time, especially after suffering significant wear and tear the galvanometers (motors) within an analogue scan head can become permanently misaligned. The only way to fix this is to recalibrate the scan head, which is a laborious task that can only be performed by a skilled professional with reasonably sophisticated equipment.

In the case where a galvanometer totally fails an analogue scan head needs to be return to the factory for repair.

Analogue scan heads are in general slower and less accurate too.

While visually there is little to differentiate the two, in all other aspects the digital alternative is a far superior product. Not only can it work faster and more accurately (sometimes up to twice the speed of an analogue alternative), it will not suffer from misalignment in the same way that an analogue scan head can.

A well designed laser marking machine incorporating the latest digital scan head technology will benefit from a self calibration process on start-up. This test process occurs during the first 30 seconds or so after powering-up the unit. Self calibration not only corrects minor misalignments but is particularly useful if, for example, one of the galvanometers fails and requires replacement because rather than having to send the whole unit back to the factory for repair the galvanometer can be changed in the field, saving significant time and costs for the repair.

Digital scan heads are faster to response to control signals, which significantly contributes to overall performance speeds. This is not only beneficial to increase throughput but also is useful in terms of system set-up too: an analogue unit can take hours to perfectly calibrate conversely a digital alternative can be set-up in a matter of minutes.

Lastly, the more efficient electronics of the digital unit contributes to lowering the overall operating temperature of the scan head, which in turns enhances performance and extends the working life of the component.

In recent times the premium to be paid for a digital scan head has reduced to near zero, so there is no longer any reason to use analogue scan heads in a laser marking machine. Therefore, should the vendor offer such a head take care to inspect the machine very carefully as it is likely other design/performance comprises have been made to the disadvantage of the customer.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Focusing a 1µm Galvo Fiber Laser Marking Machine

Accurate focusing of any laser marking machine is fundamental to achieving a successful laser mark.

When the laser marker is precisely focused, the resulting optimally sized focal point will deliver maximum resolution, higher energy density, higher productivity and a consistent mark with a desirable aesthetic.

A laser marker that is incorrectly focused will not only produce an undesirable result but it will potentially work at a far slower rate too, having a significant adverse impact on productivity.

For this reason, with every laser engraving machine that we manufacture we incorporate an electronic Z axis to which the beam deflection unit (scan head) is mounted, which is controlled by our software so that the user can precisely focus the laser.

Systems that incorporate a manual method of focusing (not controlled by software) are much more prone to operator error.

Even worse, with poorly designed machines where the worktable is moved to focus the laser rather than the scan head, significant errors are almost guaranteed. This is especially common where machines use a ‘lab jack’ type table that is often never perfectly level and/or can move during the laser marking process, especially when heavier items are loaded to the machine.

The problem of inaccurate focusing of the laser is compounded where the laser source is lower in power because any loss of energy density will be a significantly larger portion of the overall laser power. Therefore, it’s somewhat true that lasers of a higher power are more forgiving if they are used out of focus compared to the same machine fitted with a lower power laser source.

For some applications it can be desirable to deliberately defocus the laser. For example, when laser marking stainless steel with a near to black annealed effect, defocusing a machine by several millimetres can actually enhance the effect.

Marking with an intentionally defocused laser can also prevent unwanted material ablation that would otherwise occur with a perfectly focused laser. For example, when laser marking food packaging (coding), such as the foils used to wrap ice-creams, a perfectly focused laser can pierce the foil and deliver a very narrow mark that is harder to read where a defocused laser is less likely to pierce the foil and the larger focal point will provide for a wider character that is easier to read.

Also, when some products require marking at exceptionally high speed and high resolution is not a priority, using a defocused laser with a larger focal point size can allow for a lower hatch density, providing for a much faster mark. This technique can be used, for example, for marking of cattle tags.

In summary, precise control of focusing the laser is often critical to achieving the best overall result.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

A simple Explanation of Laser Safety Classifications within a Laser Marking or Laser Cutting Machine

Almost all manufacturing equipment has inherent safety risks. For most types of machinery these risks are obvious, easily identifiable through visual or audible inspection.

The laser source within a laser marking or laser cutting machine cannot be monitored by the user visually or audibly without the use of special equipment. Therefore, there are specific safety classifications given to laser devices so that the degree of hazard can be understood and the risks mitigated to avoid accidents.

All laser devices must be labelled to identify the level of laser safety hazard, called the laser safety class.

There are 4 laser safety classes according to the degree of risk with Class 1 being the lowest risk and Class 4 being the highest risk. Within some of these classes are a number of sub-classes specific to the system configuration, in particular the laser wavelength and/or its AEL (Accessible Emission Limit) i.e. the degree of power emitted from the laser and the exposure time before it becomes hazardous.

By far the greatest hazard to the user is the risk of damage to eyesight. This can be permanent or temporary depending on the power and wavelength of the laser as well as the AEL.

Other risks relate to damage to materials biological, for example damage to skin, or non-biological as well as the risk to cause fire and/or explosion when coming in to contact with flammable or combustible materials such as petroleum, flammable gases, etc.

Within a laser marking, laser engraving, or laser cutting machine the laser source at any wavelength is always Class 4. The Class 4 laser hazard can be reduced by the addition of extra safety measures and devices built around the laser source.

Class 1 defines the laser marking machine or laser cutting machine as being of the lowest risk. A Class 1 laser machine can be operated in almost any environment suitable for an electronic device and emits no harmful laser radiation whatsoever.

To meet the requirements of Class 1 the laser hazard must be contained within a 'light tight' enclosure with all access panels being used for general operation interlocked and all service panels being secured with screws, or similar semi permanent fixings, so that opening of the service panels requires the use of a tool.

When an interlocked access panel is open an indicator must show that the system has moved from Class 1 to Class 4 and power to the laser must be removed so as to prevent accidental operation.

Class 2 is essentially the same as Class 1, however, this type of machine incorporates a visible guiding laser at <1mW. Typically this will be a red guiding laser at the 655nm wavelength.

Class 3 is not typically applicable for a laser marking or laser cutting machine and is more commonly found assigned to equipment incorporating a very strong, visible guiding laser typically at 5mW.

Class 4 is the most dangerous of all the laser safety classes. A Class 4 laser marking machine exposes the user to potentially immediate and harmful laser radiation as well as adds risk for damage to materials that can combust and/or explode. Use of a Class 4 laser must be restricted to a specifically designated and appropriately signed area, segregated from the general work area. Operators of Class 4 lasers should be specially trained and advised of the risks as well as wear specifically configured PPE while working in the designated Class 4 area.

In a perfect world only Class 1 or Class 2 laser marking or laser cutting machines would exist but in some circumstances the safety enclosure becomes an obstacle to the process. In such case Class 4 lasers are required, however, a Class 4 laser should never be operated without the owner and user being fully aware of the safety risks and having in place safety measures to prevent unnecessary accidents.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Why to Use the 9.3µm Wave length for Laser Marking and Laser Cutting

The vast majority of gas lasers in use today are CO2 lasers operating at the 10.6µm wavelength where there are literally hundreds of thousands of lasers working every day for laser marking, laser engraving and laser cutting applications.

In recent years some of the main laser technology manufacturers have introduced a more specialised version of their 10.6µm lasers modified to operate specifically at the 9.3µm wavelength.

Some materials, such as Polyethylene terephthalate (PET) for example, can be laser marked at the 10.6µm wavelength but will react better at the slightly shorter 9.3µm wavelength.

PET is a thermoplastic best known as a material to manufacture synthetic fabrics for clothing (commonly known as polyester) and it is also used to manufacture bottles containing drinking water, carbonated pops, fruit juices and other beverages.

In the case of a beverage bottle the vessel must be marked with coding such as date of manufacture, date of expiration (use by date) as well as other variables such as product type and batch numbers. Laser marking is a great technology for this process as a laser engraved code can be applied directly to the PET vessel so that it is wear resistant, fast, cheap, difficult to alter/counterfeit and eco-friendly to produce as there are no inks involved.

Using a 10.6µm laser marking machine to mark PET directly creates a clean, glossy mark with some material ablation. When filled with liquids that are highly transparent, such as water for example, the 10.6µm laser engraved code can be low in contrast and therefore hard to read.

When the bottle is filled with a carbonated beverage the engraved (ablated) area can cause a weak spot that in some cases can cause the vessel to fail and the liquid escape, wasting the product completely. This is an increasing problem as bottling plants move towards thinner walled vessels to aid in lowering material use and product cost/weight.

Using the same laser marking machine but at the 9.3µm wavelength creates a different material reaction where the laser marking is frosted in appearance without any ablation taking place, thereby increasing the contrast and readability of the mark no matter what the contents are and reducing the risk for failures of the vessel near to zero.

PET is also used in some specialist applications. For example, it can be combined with PVC to make a film used for the hologram on a credit card. Here, a specifically configured laser cutting machine at the 9.3µm wavelength can kiss-cut the surface film without piercing its backing film with a far cleaner edge and less adverse heat reaction than a similar machine would produce with a 10.6µm laser. Therefore, using the 9.3µm laser for this laser cutting process increases output quality while simultaneously reducing waste through rejected parts.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Why Laser Marking is Fast Replacing Printing

For many years Continuous Ink Jet printing (CIJ) has dominated the industrial sector for coding applications such as, for example, applying time/date/batch codes to food and beverage packaging.

During recent years, laser marking technology has seen a significant improvement in both performance and reliability simultaneous to a lowering of prices. These advancements now make laser marking a viable alternative to CIJ.

In terms of the code itself, laser marking offers many advantages over CIJ.

The CIJ process utilises ink, which as a consumable is costly to purchase over time and the printing heads of CIJ must be constantly cleaned and/or replaced too. A laser marker has no consumables, so running costs are far lower, as is the requirement for maintenance.

The low requirement for maintenance of a laser marking machine can mean that it’s a far more reliable method compared to CIJ and the fact that the laser uses no ink makes the laser marking process more environmentally responsible too.

In cases where the mark requires the application of logos as well as simple coding, here the laser is often a much better solution. CIJ is very limited as to what type of mark it can produce and over what area but a laser marking machine can deliver a wide variety of graphic formats from logos to barcodes to simple text and over a much bigger area too than a CIJ can apply.

For the mark itself, a laser mark is permanent and difficult to counterfeit. CIJ is quite the opposite; for example, when coding milk cartons by CIJ it is common for the mark to rub off as the carton is exposed to temperature changes, condensation and wear. A laser mark is resilient to such things.

A laser marker can also be easier/better to integrate to production lines. With CIJ the head is commonly positioned close to the surface to which it is printing. With a laser marking machine it is possible to place the beam deflection unit (sometimes known as the scan head) several hundred millimetres away from the product being marked.

A laser mark can add significantly to the perceived value of the item itself. For example, for a recent project we configured a fiber laser marking machine to brand stainless steel razor blades. Historically the blades were marked by CIJ. The aesthetic of the laser mark was significantly better, raising the perceived value of the item itself and addressing the counterfeiting issue our customer was having with their product marked by CIJ.

CIJ is a single process solution; i.e. it is simply a surface print. In some cases it’s possible for the laser to code and produce other processes at the same time such as, for example, perforation of packaging or cutting of thin films

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

When to Use a DC or RF Laser for Laser Cutting

At the heart of every 10.6µm laser cutting machine is the laser source. For low power (<100w) laser cutters there are two different types of laser source most commonly available.Both are essentially gas lasers emitting a laser at the 10.6µm wavelength but here the similarity ends. We cover the specification and manufacture differences between these technologies in other articles.

The oldest, most stable and reliable, highest performing laser is the RF variety. A high quality RF excited laser can produce excellent beam quality with a very short (fast) rise/fall time. This makes the RF laser ideal for laser cutters where the process needs to be delivered at high speed.

RF lasers are also much better for applications that require a high degree of detail to be cut. This is because when the motion system slows down to turn an acute angle or change in direction, to avoid burning-out the material where the motion system turns/dwells the laser power must be ramped down proportionally. DC lasers are difficult to control when ramping, often producing unreliable results.

The high-speed pulse of the RF laser is also much better suited for laser cutting materials that react adversely to overheating where the RF laser will minimise this undesirable reaction. For example, laser cutting wood with an RF laser can produce a cleaner edge than when using a DC laser. Another example would be the laser cutting of thin materials, such as laser cutting veneers where too much heat can cause the material to warp. Using an RF laser will again minimise this adverse effect.

Another preferred application for using an RF laser is where the cutting control needs to be very precise: for example, the laser kiss-cutting of labels where the laser cuts the surface material but not the backing paper. This application can require the use of very low laser power, even just a few watts. All gas lasers do not work well when the duty cycle falls near to or below 10%. For DC lasers at 60w we find they do not perform well below 30% (18w), which is often too much power for kiss-cutting.

A DC laser is best applied to laser cutting materials that work well with heat and where the duty cycle is almost always 100%. For example, laser cutting acrylic, especially at thickness >3mm (1/8”) where the slower pulse and greater heat of the DC laser can be an advantage. In this example a DC laser will often laser cut acrylic with a far smoother edge than its RF alternative.

Of course, DC lasers being a fraction of the price of the RF alternative means the user can afford to use a far higher DC laser power than the nearest cost RF alternative closest in price. This means that using a higher power DC you can cut thicker materials much faster. For example, one of our 30w RF machines actually costs more money than the same machine fitted with a 100w DC laser. In this example, the DC version would cut thicker materials near to three times faster.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Laser Marking Stainless Steel With a Black Annealed Effect

Stainless steel is an excellent material for laser engraving at the 1µm wavelength where a range of different effects can be produced such as ablation (engraving), thelaser marking of various degrees of shading from light to dark and even a limited range of colours can be produced too.

One of the most visually appealing of laser marked effects is dark annealed stainless steel where the near jet-black effect of the laser mark contrasts beautifully with the clean and crisp surface of the stainless steel finish.

This type of mark is high in contrast and is often used to increase the perceived value of products that are marked in this way.

The colour change occurs by using the laser to heat the metal and create within it an oxide layer. Colours and shading will vary according to the amount of heat generated during the laser marking process.

A laser marking machine with a higher laser power can produce these types of mark at a much faster rate than a lower power laser marking machine.

For a laser engraver with a lower power, the feed rate (speed of beam delivery) will need to be lowered in order to expose the material to the laser for longer and generate enough heat. Even more heat can be added by closing the distance between the hatch lines in the graphic thereby multiplying the degree of overlapping of the focal point from hatch line to hatch line. Even more heat can be generated by delivering the hatch in a localised way; hatching small connected areas at a time.

The smoothest, most uniform results are achieved by deliberately marking the material out of focus (defoucused). This provides for a much larger, softer focal point to add even more heat. The required degree of defocus will vary depending on the configuration of the machine. How far to defocus in order to achieve the best result is initially a trial and error process but once the ‘sweet spot’ is found the process is easily repeatable.

If using a lens with 163mm f/l (110mm work area) the sweet spot is usually found between 3-5mm defocus. When using a lens with 254mm f/l (180mm work area) the sweet spot is usually found between 7-9mm defocus.

The oxidised layer of annealed material will only be approx 20-30µm in depth. Therefore, this is not a particularly hard-wearing form of laser mark. To produce a harder wearing mark it is possible to fist ablate (engrave) the steel then to anneal the material to further darken it. While this type of mark is certainly more resilient to wear and tear it is however not a visually smooth and lustrous as a mark annealed without ablation. Using a machine with a Z-axis that is controllable by software is essential for this process.

Even further enhancement can be achieved by first lightening the surface of the material with the laser delivered at an alternative angle, such as 45 degrees for example, then annealing over it with further passes. This procedure can produce a near to black on white effect for maximum contrast.

The laser annealing process can raise the stainless steel to nearly 600c, so this is not a suitable process to apply over large areas and/or to thin material as to do so can cause the material to deform. Materials that do not have a flat surface are not suitable for this process.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Laser Marking Polycarbonate

Polycarbonate (PC) is a thermoplastic that can be purchased in sheet form as well as a granular form for use in plastic moulding or extruding machines.

PC is a strong and lightweight material, with good properties for shock absorption and electrical insulation. Polycarbonate is easy to thermoform and is available in various transparent and opaque varieties, therefore, polycarbonate can be found as a base material in many products from the casings of electronic devices to windows in aeroplanes.

When laser marking polycarbonate a laser operating at 1µm or lower is required. Laser marking machines at longer wavelengths, such as 10.6µm (CO2 laser) will simply cause the material to melt.

When exposing polycarbonate to a 1µm fiber laser marking machine the material will undergo a carbonization process: this is where the carbon within the material is released to show a contrasting grey to jet-black result. The greater the degree of exposure, the darker the result.

Laser carbonization of polycarbonate is visually appealing and normally of a high perceived value. The mark can be made to penetrate deep into the material, so it’s very hard wearing too. Laser marked polycarbonate is therefore often found on machine control panels and other such functional devices.

When using a lens with a short focal length it is possible to laser mark photos to polycarbonate with incredible resolution and quality.

Using a 1µm fiber laser marking machine it is also possible to foam polycarbonate. This process occurs when the material is sufficiently heated by the laser engraver to a point where gases are released and the material bubbles then reforms raised slightly from the surface of the original material.

As well as laser marking with excellent contrast, it is also possible to laser mark polycarbonate at extremely high speeds using even the lowest powered laser source. Therefore, laser marking polycarbonate is often a viable alternative to other forms of marking such as pad printing, for example.

Laser marking applications for polycarbonate can range from laser marking ID cards, to laser marking phone cases, to laser marking meter boxes.

Laser marking polycarbonate with a shorter wavelength laser such as 532nm (green) or 355nm (UV) can produce even higher detailed results. These short wavelength lasers also produce less thermal reaction within the material.

Laser marking polycarbonate is a clean process with near to zero waste as a by-product. It is therefore no surprise that many thousands of laser marking machines are dedicated to laser marking products made of polycarbonate.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Laser Cutting and Laser Marking Foils With a 1µm Laser

The use of micro-thin foils is widespread across several industries such as food packaging, electronics and the medical sector to name but a few.

These types of foil can be manufactured from a variety of metals and sometimes incorporate plastics too, especially in the form of surface films.

One such example would be the use of aluminium foil to seal the openings of polypropylene test tubes used within the medical sector to contain and grow biological samples and cultures. The foil can be laminated between two lasers of plastic; the surface layer acts to protect the aluminium from scratching/tearing or prematurely perforating and the underside layer is used as a catalyst to help affix the foil to the rim of the tube and form a perfect, strong and airtight seal.

In this example a number of these plastic tubes will be loaded to a tray, biological samples placed within the tubes, then one sheet of laminated foil is used to seal all of the tubes within the tray. Historically, the tray will then pass to a punching process where steel tools will cut away the unused material, in the process separating one tube from the next.

The process described above places a high degree of wear/tear on the steel tools, which require frequent replacement. Also, the user has no way to adjust the cut and this contact method of cutting produces a high number of rejects through broken seals or damaged tubes.

By replacing the physical cutting tool with a laser cutter, the non-contact process is more accurate, cleaner and can be faster too. As there is no tool to blunt, there is no degradation in the quality of cut even when the production volumes are high, so the degree of rejected product is minimal if any at all.

In the past we have used several configurations of 1µm fiber laser machine, primarily configured as a laser marking machine, to cut these types of foil. When laser cutting foil the system parameters as well as the number of beam delivery passes can be adjusted to create the ideal cut.

An added benefit is that the same machine being used for laser cutting of the foil can also be applied for laser marking too.

In the food industry it is common to find a 1µm fiber laser marking machine applying UID marks, such as barcodes and manufacturing time/date and other such marks to the wrappers of ice-cream, potato chips (crisps) and other foods that are commonly foil wrapped.

At Lotus Laser Systems we manufacture a wide range of technology solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

How Materials React to a Laser

There are generally three ways that a material can react to a laser: Engrave, mark or cut.

Laser engraving is defined when material ablation (removal) occurs. In this case the laser engraving machine will vaporise some of the material to create some depth.

Some materials can only be laser engraved, such as wood for example. In other words, the material cannot be exposed to the laser without some ablation occurring, however, in this example ablation is desirable because the perceived quality and value of laser engraved wood is further enhanced when there is a significant degree of ablation.

Some materials work well with minimal ablation but react adversely when over-exposed to the laser. Cast acrylic is a good example in this case where some ablation by a 10.6µm laser creates a beautifully lustrous effect but when over-exposed the engraving can become very powdery and tainted by an adverse reaction to an excessive degree of thermal stress.

Laser marking constitutes the majority of laser applications and is where the material reacts without ablation to show a contrast between the area exposed to the laser and the area that has not been exposed to the laser. Laser marking is usually some form of colour change but can also include a reaction called ‘foaming’. Foaming is a material specific phenomenon that occurs when the laser marking machine heats the material to release gasses that raise and then solidify above the surface of the material.

Polycarbonate is a good example of a plastic that if exposed to a 1µm laser will colour change and foam with a highly contrasting and desirable effect.

Laser marking without ablation can provide for an incredibly detailed result, at super-high speeds and with zero to minimal adverse reactions from the base material.

Some materials can be laser marked or laser engraved according to the system configuration used and the laser parameters set. For example, a CO2 laser at the 10.6µm wavelength can only mark the surface of anodised aluminium. Increasing the intensity of the exposure can cause removal of the anodised surface but this is not very noticeable. Using a solid state laser, like a fiber laser at the 1µm wavelength, the same material can be surface marked or ablated to a considerable depth.

Laser cutting occurs when the laser vaporises the entire thickness of the material to create a void from upper to lower surface.

Solid, flat sheet materials are used for the vast majority of laser cutting where highly accurate and detailed cuts can be made by the laser that are impossible to produce by other forms of cutting technology.

For example, laser cut acrylic provides for an instantly polished edge and some textiles, such as silk for example, are heat-sealed by laser cutter where they may otherwise fray.

For some applications a finely controlled cut takes place by the laser. For example, ‘kiss-cutting’ of adhesive labels where the adhesive surface is laser cut but the backing material is not and also, the laser scoring of some materials to form a line that can form a break point, for example for snapping-off labels out of a sheet format.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Cooling of a DC Glass CO2 Laser

DC excited (glass) CO2 lasers at the 10.6µm wavelength are rapidly growing in popularity and fast overtaking the number of RF (metal) lasers sold, especially in the more price conscious markets such as laser cutting machines for schools and laser engravers for hobbyists.

Compared to an RF alternative, DC lasers have limited functionality, lower performance and a much shorter working life but they do offer the possibility of owning a laser cutter to some that would otherwise never be able to afford a laser cutting machine with an RF laser source.

All lasers require cooling and these days modern RF lasers are all cooled by air. DC lasers, however, are a less efficient technology and generate more heat as a by-product of the process so all DC laser need to be water-cooled.

Cooling the laser effectively and efficiently is a critical process. Failure to do so will cause massive fluctuations in the performance and reliability of the laser cutter, significantly shorten the working life of the laser itself and can in some cases lead to a premature, catastrophic laser failure.

Some very low cost machines ship with no more than what is an aquarium pump for the cooling device. Such devices are wholly inadequate as they do no more than to recirculate increasingly hotter water around the laser tube, some with variable rates of flow and pressure too.

For the laser to be cooled efficiently and effectively the coolant (water) must pass through a device specifically designed to control its temperature. In a laser cutting machine this device is called a chiller, although this can be a bit of a misleading description because the chiller will only actually reduce the coolant temperature after it reaches a set-point. It is therefore an ‘on-demand’ device, continually monitoring and keeping the coolant temperature constant.

Most chillers will use deionised water for the coolant, which helps to keep both the coolant and the internal workings of the laser clean. No matter what the coolant type the chiller must be regularly monitored and maintained to ensure that it is performing correctly.

Periodically, the chiller should be drained, the internal workings of the laser flushed and the chiller replaced with new coolant. Care should be taken to ensure that any air filters/vents on the chiller are also regularly cleaned/replaced. DC lasers are a consumable part. When replacing the laser the user should never use a chiller containing old coolant

The chiller should not be placed above the height of the laser. Ideally, it should be placed on a stable surface approximately 500mm from the floor and away from all other electrical devices. This minimises the likelihood of contamination of the cooling veins.

Pay careful attention not to allow the workplace to fall below 0c as this will cause the coolant to freeze and the chiller and the laser to become damaged.

Most DC lasers <100w work best when operated at a set temperature of 21c. If the laser cutting machine is within an environment that has a high temperature and/or relative humidity the operating temperature of the chiller should be set with 10c of the dew point, otherwise, condensation may form on the internal workings of the laser and the chiller causing a short. At maximum the chiller should not operate above 24c.

Maintaining an effective cooling device for your laser can save you significant time/money and prolong the life of your laser cutter.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Hatch Settings for Laser Engraving

To simulate a solid (usually black) effect within artwork a laser engraving machine will follow a series of parallel lines to ‘fill in’ the solid area in a way similar to what you would shade between outlines on paper with a pencil.

For a plotter format laser engraving machine this software parameter is called ‘DPI’ or ‘resolution’ and for a galvo laser engraving machine it is called ‘Hatch’. For the purpose of this article we’ll call this parameter ‘hatch’.

With a plotter laser the options for adjusting the hatch parameters are very limited. All plotter lasers are constraint to engrave (raster) at one angle, this being zero degrees (left to right) so all plotter lasers only allow for one hatch variable, which is the distance that can be set for the spacing between the hatch lines selected from a list of approximately 6 or so predefined spacing. For example, 1000dpi, 600dpi, 333dpi and so on.

A better designed plotter laser engraver and all galvo laser engravers will allow for the hatch spacing to be set as a unit of measurement, usually down to increments as small as 0.01mm. This provides for a wider range of engraving effects as well as more flexibility to balance the job speed with the output effect and quality of the laser engraving.

Galvo lasers offer the very widest range of hatch parameters because all galvo laser engraving machines can hatch at any angle (a full 360 degrees) and most will have additional controls for the start/stop of the hatch line and also how the laser is control as the motion controls turns out of one hatch line and enters into the next.

The biggest influence on output effect is the hatch spacing and hatch angle. For some jobs a smaller distance between hatch lines will not only increase the resolution of the engraving but it will also influence how the material reacts with the laser. For example, smaller values for hatch spacing can produce on some materials, such as laser engraving stainless steel, a darker effect but add significantly to the process time.

Conversely, a low hatch density (larger hatch spacing) will not only provide for a much faster, lower resolution mark but on some materials it will cause a completely different effect, such as for example a silver effect on stainless steel.

When setting the hatch values it’s also important to consider the material type as well as the characteristics of the lens being used because these factors also determine the maximum achievable resolution.

If using a galvo laser engraving machine, experiment with multiple hatch angles that overlap each other. For some materials this will not only help to darken and deepen the laser engraving but it will also help to make the effect much smoother too.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Laser Cutting and Laser Engraving Leather

Leather is a general term predominantly used to describe some form of hide (skin) that can be natural (of animal origin) or synthetic (man-made). If at all possible, when laser engraving or laser cutting leather try to use synthetic materials. Not only is this morally responsible but often the job is easier to achieve with a more predictable result due to the consistent nature of a man-made product compared to a natural animal hide.

There are a multitude of different colours, thickness and types of leather. Leather can be plain in finish, embossed with patterns or even retaining fur or hair.

When laser cutting or laser engraving leather the best laser wavelength to use is a CO2 laser at 10.6µm.

When laser engraving leather the best effects are produced by using lighter colours, such as tan or even better results can be achieved using colour dyed leathers where the contrast can be further enhanced.

One of the main obstacles to overcome is the adverse reaction that leather can have to the heat of the laser engraver, particularly when laser marking over larger areas. One way to overcome this is to pre-soak the leather before it is placed within the laser engraving machine. CAUTION: do not place wet materials inside the laser machine! Prior to attempting this technique seek detailed advice from our support department.

When pre-soaked the excess moisture within the material acts as a heat-sink to minimise the material warping and/or excessively charring during the laser cutting and laser engraving process. The retained moisture also adds weight to the leather, which minimises it from moving as air flow across it from the laser fume extraction unit.

After laser engraving, some types of leather can be further enhanced by rubbing hand cream or sun lotion onto the material to moisturise it and provide for a luxurious looking lustre, especially where it has been intensely laser engraved.

If using leather with hair, such as cowhide for example, some visually stunning effects can be produced by setting the parameters of the laser engraving machine to remove the hair but without marking the hide beneath. The results can be very eye-catching, similar to some hairstyles supported by basketball players! One examples of this technique is use the hide associated with one type of animal but etch it with a fur pattern associated with another type of animal.

Commercial applications for laser cutting and laser engraving leather range from decorative marking and branding of wallets, purses and handbags to cutting intricate patterns for shoes or even the creation of decorative hides to be used in manufacturing footstools.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Nucleation of Beer Glasses by Laser Engraving

Nucleation is a process whereby the inner surface of a drinking glass is marked to provide for a roughness to which the gasses from carbonated drinks, such as beer, will be attracted and released into the liquid at an accelerated rate.

There are several ways to mark glass like this but none come anywhere near to being as fast, effective, clean or low in cost to produce as a CO2 laser marking machine.

Compared to a standard glass, after the drink is poured, a nucleated glass will enhance the visual appearance of the liquid by making it look ‘fizzier’ and in particular with lager beers it increases the volume of the frothy head, characteristics that are highly desirable to both the seller and the consumer.

When comparing a nucleated glass to one that is not nucleated the difference in effect of the appearance after pouring can be massive. By comparison, the non-nucleated glass will show a liquid that looks very flat.

To reach into the bottom of a pint glass requires a significant degree of clearance from the lens of the laser engraving machine. There is also the speed of the laser marking to consider too. Therefore, the only viable system configuration for this process is a galvo delivered CO2 laser engraving machine at the 10.6µm laser wavelength.

Not much laser power is required for nucleation. A 45w laser is usually sufficient

A typical nucleation mark by a galvo laser engraver will be produced in approximately 1 second. Therefore, when combined with well designed automation for handling the glasses it is possible to laser engrave well in excess of 3,000 glasses per hour with a single laser engraving machine.

As no material is vaporised during this process there is no requirement for fume extraction; somewhat of an exception compared to most other applications where a CO2 laser engraver is used.

As with all laser engraved glass, it is very important to balance the laser parameters well so as to create enough of a mark to work well and look good but not too much so that the glass engraving starts to fracture and splinter. Once the machine parameters are perfected this type of system will work reliably and consistently 24/7 with near to zero required maintenance.

Compared to conventional glass marking processes, another major advantage of laser engraving glass is the ease with which the content can be changed. It is in fact quite possible to create marks that are individual from one glass to the next without any user intervention.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Laser Engraving Stone

Laser engraved stone can have a stunning visual impact, especially laser engraving photos to granite.

Not all forms of stone will laser engrave so careful selection of the material is important. Stone is a general term that can be used to describe two distinct materials:

1. Naturally occurring stone, mined from the ground and shaped by breaking, sawing, cutting, grinding and polishing. Examples would be granite, marble or slate.
2. Man-made stones, also known as synthetic, composite or engineered stone such as alabaster, quartz and a range of trade names the most famous of which is Corian. These composites contain a blend of natural stone materials encapsulated by bonding resins such as acrylic. Composite materials are available in a wider range of finishes, more consistent in their make-up and are much easier to machine into shapes.

Each different type of stone will laser engrave with differing degrees of effect. Most natural materials will not vaporize. Laser engraving granite, for example, produces a result that is very similar to laser engraving glass where the highly polished surface fractures when pulsed by the laser with little to no depth.

Softer materials such as some types of marble and most of the composites will to a varying extent vaporise with some depth. This can be beneficial if, for example, it is desired to paint-fill the laser engraving to nhance the visual impact.

Materials that are dark in colour and more uniform in their make-up produce the best results. For example, some of the best effects that we have seen have been to carefully selected, black marble or granite that shows minimal flecks or veins in the material. If the stone has too much character this can irregularities in the mark and interfere with the image too.

Also important is the selection of the laser wavelength. For the majority of laser engraving to stone a CO2 laser at the 10.6µm is used. This type of laser is required especially when laser engraving composites with depth.

However, some materials such as slate, for example, can be marked with amazing detail using a fiber laser at the 1µm wavelength. This type of laser produces a focal point that can be x10 smaller than a CO2 laser and so the resolution can therefore be x10 higher.

Flatness of the material is important too, especially for stone that is Riven such as slate, for example. Too much variation in height will cause the laser to defocus and produce and undesirable result.

Last but not least, it’s important to note that stone is a very heavy material. With most machines there are limitations with regard to the weight of the material that can be loaded to the worktable. In such cases a workaround can be to use thinner stone tiles that after laser engraving can be mounted to a larger stone backing.

Some laser engraving machines exist that are specifically designed for use by monumental masons. These types of machine generally use a gantry mounted laser to move the laser over the stone. This type of machine is very limited in scope and is generally not well suited to a wider range of laser engraving applications.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions ideally configured for laser cutting and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.

Laser Cutting Wood

Insofar as laser cutting is concerned, wood can be separated into two distinct groups:

1. Natural timber from various species of tree. For example, maple or cherry wood.
2. Man-made wood manufactured by bonding wood pulp, fibers or shavings. For example, MDF or plywood

All natural timbers can be cut by a CO2 laser at the 10.6µm wavelength. Limitations only apply with regard to thickness and the degree of charring that is acceptable to the customer.

Special versions of laser cutting machine are made for specific wood cutting applications such as, for example, laser cutting plywood for label dies. However, for the purpose of this article we are referring to a typical benchtop format laser cutter <100w.

For most industries laser cutting anything beyond 12mm natural timber and 9mm plywood produces an undesirable result because the feed rate (speed of cut) combined with optical limitations causes the wood to adversely burn.

When laser cutting wood the rate of laser fume extraction, particularly underside extraction and air assist delivered through the nosecone, can never be too much. When vaporised, wood produces a very dense fume that if not immediately evacuated from the cutting line will rise into the path of the beam and absorb laser power, significantly dropping the feed rate of the cut and in turn accelerating the degree of charring at the edge of the cut.

High amounts of debris from laser cutting wood can also contaminate laser optics causing them to fail prematurely and also cause HAZ (Heat Affected Zone), which is an undesirable staining to the edge and surfaces of the material.

In machines where the design of extraction is poor, surface HAZ can be minimised by first applying a low-tack, paper based tape to both surfaces of the wood. The tape acts as a masking barrier, attracting the contamination. After laser cutting the paper is removed and the wood surface underneath is clean.

Natural timber has a tendency to warp, which is challenging for laser cutting as this causes the beam to defocus, producing undesirable results. Therefore, if the application calls for laser cutting of natural timber it is best to process the material as soon as possible after receiving it from the mill.

Man-made or engineered woods can contain resins that are actually designed to be fire retardant. This is unhelpful when trying to burn through the wood with a laser cutter! Therefore, if the application calls for using a form of engineered wood it’s wise to be very selective about the exact type of material you use. For example, plywood is most commonly available in a WBP or exterior grade. The resins used to bond this type of plywood are among the least laser friendly and will resist thelaser cutting process, accelerating HAZ.

Interior grade plywood, sometimes called white glue plywood, is among the most laser friendly plywood’s. Not as commonly available as exterior grade, interior grade should be used as a preference for laser cutting if the job specification allows it as the resins in the material will vaporise much cleaner.

An often overlooked aspect is that of the surface finish of wood prior to laser cutting. If the part to be laser cut is the finished item then the surface should always be sealed/finished before it is laser cut. This reduces HAZ and any HAZ present can be wiped off with a slightly damp cloth. If however the material is to be post processed, such as sanding for example, then pre-sealing the wood is not absolutely necessary as the HAZ will be removed during post processing.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions ideally configured for laser cutting and laser engraving wood. Our experts would be happy to recommend which configuration best suits your application.

Laser Engraving Photos To Wood

Many owners of a laser engraving machine will tell you that laser engraving wood has to be the best looking effect that alaser engraving machine can produce.

This is especially true for laser engraving a photo to wood where the grain of the material can have a significantly enhancing effect on the image itself.

All natural timbers and most engineered wooden boards can be laser engraved by a CO2 laser at the 10.6µm wavelength but some natural timbers will not mark with contrast. Therefore, when selecting timber for photo laser engraving it’s wise to consider this point to gain maximum effect.

Timbers that contain a high oil content generally vaporise with a good contrasting effect. Cherry wood and maple would be too of my favourites. These woods also tend to have quite fine grains that enhance but do not interfere too much with the image itself. Oak, for example, is not a favourite of mine because the coarse variations in the look and density of the wood can detract from the effect of the image being marked.

Although it is a slow machine, a plotter format laser engraver is best suited where the application requires a mark made over a large area and especially where a high degree of detail is required because the Plano convex lens of the plotter produces the smallest possible focal point, which provides for the highest possible resolution.

Just note however that even when using a lens with the smallest possible focal point, the size of the pulse into wood is far larger than with other materials that vaporise, such as cast acrylic, and certainly a lot larger than materials that do not vaporise, such as laser marking anodised aluminium. This is because the pulse into wood continues to grow in size a little after the pulse has been delivered and also that in order to achieve a good, contrasting effect, most laser engraving to wood has some depth (deeper = lower resolution).

When using a plotter, in terms of resolution it is not beneficial to raster engrave with hatch spacing greater than 0.08mm (300dpi). Higher resolutions can in fact cause the dot pattern to merge and reduce the perceived resolution of the laser engraved photo. Some of the best photo etching to wood work that I have seen has actually been produced with a hatch spacing 0.10mm (250dpi).

Good system software will allow you to adjust the dot pattern of the image at the laser engraving machine itself, however, for machines that do not provide for this, such as those that work via a print driver, it’s important to match the graphical image resolution with the resolution of the machine itself (image resolution in dpi = focal point size and hatch spacing).

Laser engraving photos to wood is quite a slow process and if this is your core business then nothing beats the speed of a galvo laser. Typically, for this process a galvo laser will be somewhere between x3 and x10 (or even faster!) than the speed of a plotter for this application. Therefore, if you plan to grow your business in this field and so long as the image is no larger than 175mm (approx 7”) consider carefully investing in a galvo laser engraving machine because a single galvo system can be an overall much lower cost investment as it can produce at the rate of a whole factory full of plotters and with far lower maintenance issues too.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions ideally configured for laser cutting and laser engraving wood. Our experts would be happy to recommend which configuration best suits your application.

Laser Marking and Engraving Glass

The word ‘glass’ is an all encompassing name given to materials that can have significant variations in chemical and other properties, however, it is most commonly used to describe various forms of silica based transparent materials that are often quite fragile in nature such as spectacles, drinking vessels, vases, etc.

Aside from the chemical differences in many forms of glass, variations in process of manufacture contribute towards making glass a material that is somewhat wide in scope and inconsistent in make-up. Even glass of the same make-up and shape can vary in size due to thermal inconsistencies during the cooling process, therefore, unlike most other materials glass can be difficult to laser engrave with a highly consistent effect.

At shorter laser wavelengths glass is generally transparent, allowing the beam to pass through. For example, the lower layer of a 1µm f-theta lens found in a laser marking machine is made from glass. However, with a specially configured 532nm green laser it is possible to mark some forms of glass within the material itself to create some stunning effects.

For surface laser marking glass the 10.6µm laser wavelength is most suitable.

When marked by laser glass will not vaporise. When exposed to a 10.6µm laser, glass thermally reacts and micro cracks are formed. During the laser marking process it’s very important not to thermally overload the material as the desired micro cracks will form into larger material fractures that will flake away from the main body of the material causing an undesirable effect. To minimise this risk, techniques like marking through wetted newspaper or marking through dish soap are often used where this surface applied additive acts as a heat-sink to minimise any thermal overload to the glass itself. Use of such additives can however significantly reduce throughput.

Aside from the laser wavelength the optical configuration of the laser engraving machine has the biggest influence on how glass appears after it is laser engraved. The focal point of a galvo laser can be as many as x5 the size of a typical plotter laser. Therefore, marking hatch filled designs is best performed by a plotter laser. When using a galvo laser the best results are created by only marking vector lines.

The plano convex lens of the plotter format laser engraving machine provides for the smallest possible focal point, as small as 90µm, which delivers a high energy density and a very locallised thermal reaction the result of which is a mark closest to resembling that of chemical etching or sand blasting. This type of machine is best used for marking higher value items such as presentation awards, for example.

However, laser engraving glass with a plotter laser can be a very slow process, often taking minutes to produce.

For more industrial applications a galvo laser is often the only system that can be used because it will create a mark in mere seconds. Actually, for simple marking applications like laser marking wine glasses with volume fill lines a galvo laser can produce a mark well under a single second, so fast that the mark will appear after the laser has finished; much the same way that the sound of thunder can follow the flash of lightening.

Today, most plate glass for fenestration is marked by a 10.6µm galvo laser and whole new processes such a nucleation of beer glasses can only be produced with this type of laser marking machine because aside from the rapid marking speed a very long focal length is required for the laser to reach into the bottom of the glass.

At Lotus Laser Systems we manufacture a wide range of laser marking, laser engraving and laser cutting machines. Our experts would be happy to recommend which configuration best suits your application.

Laser Cutting and Laser Engraving Acrylic

Polymethyl Methacrylate (PMMA), more commonly known simply as acrylic, sometimes with the trade names of Perspex or Plexiglas, is one of the most popular of all materials to laser cut or laser engrave.

Available in a huge range of colours and finishes, acrylic is easy source, relatively inexpensive and easy to fabricate. It’s no surprise then that acrylic is one of the top plastics used for making signs, point of sale displays and machine guards to name but a few uses of this amazingly versatile material.

Acrylic is manufactured by one of two processes: Cast or Extruded .

Each process produces a material with slightly different physical, chemical and machining properties.

Cast acrylic is by far the best material to use for general applications. It has better scratch resistance and transparency and is available in a wider range of colours and thickness. It has a higher melt point so when laser engraved it will result in a clean, off-white frosted effect similar to that of sand blasted glass.

Extruded acrylic is lower cost and of a more consistent thickness. Its lower melt point provides for an almost polished effect when it is laser engraved, which provides well for processes such as reverse paint filling and it is easier to thermoform into shapes.

In a laser cutter or laser engraving machine shorter wavelength lasers cannot be used for laser cutting or laser engraving acrylic as they pass through the material. Acrylic absorbs the 10.6µm laser wavelength, more commonly known as a CO2 laser. At this wavelength acrylic acts as a waveguide, which allows for a far greater thickness of material to be cut than other materials that do not waveguide, such as wood for example.

When laser cutting acrylic the constant wave (CW) properties of a DC (glass) CO2 laser provides for a superior smooth polished edge.

When laser engraving acrylic the superior beam quality and speed of pulse of the RF (metal) CO2 laser provides for a excellent uniformity of mark and a higher resolution too, especially when laser engraving at high speed.

If the job allows, the protective film should be left on while the acrylic is cut and careful consideration should be given to the type of machine table used because acrylic is easy to damage through backward laser reflection. A table with lamella bars is by far the best to use to minimise this.

Careful attention should be given to the rate of extraction and air assist delivered through the nosecone. Too little and the material may flame, potentially catching fire; too much and the degree of polishing of the edge will be diminished.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions ideally configured for laser cutting and laser engraving acrylic. Our experts would be happy to recommend which configuration best suits your application.

Cooling for a Low Power CO2 Laser

CO2 lasers generate heat as a by-product of the beam generation process. If this heat is not removed effectively it can cause the laser to overheat and at best perform unreliably and shorten the working life of the laser or in a worst scenario the laser can fail catastrophically.

An effective and efficient cooling mechanism is therefore a vital element of the laser cutting or laser engraving machine design and function.

For low power (<100w) laser cutters there are in simple term two types of laser source:

1)DC excited; generally made from glass

2) RF excited; generally made from metal with some now being made from a ceramic.

DC lasers are significantly less efficient than RF lasers and as a consequence they generate a higher heat load so they must be water-cooled. Most modern RF lasers are so efficient that air-cooling is perfectly adequate up to 100w.

Air-cooling is performed by positioning a number of fans around the laser cavity and by moving ambient temperature air over the surface of the laser the heat is removed. Air-cooling is a much tidier, lower cost method of cooling a laser, however, it can be somewhat noisy, especially for higher power lasers where the air flow must be increased to remain effective.

Water-cooling RF lasers is a more reliable and efficient cooling method, however, it adds significantly to the cost of the laser cutting machine so it’s not common to find RF lasers being water-cooled that are <100w. Higher power RF lasers generate significantly higher heat loads and so must be water-cooled.

All DC lasers require water-cooling. Some very low cost machines incorporate what is no more than an aquarium pump to recirculate a reservoir (a bucket) of water. This is a wholly inadequate and somewhat unsafe design for cooling a laser as the water temperature will consistently rise to a point where the coolant (water) is too hot to effectively remove heat from the laser. Also, it is wholly unsafe to have open containers of water close to any electrical device.

Professional, well designed laser cutting machines incorporating a DC laser will use a specifically configured recirculating water chiller. Here the coolant is pumped around the laser to pick-up the heat then returned through a cooling mechanism, which lowers the coolant to a set temperature. The function is similar to that of a radiator in a car. The coolant temperature is monitored by the unit, which self-adjusts to increase/decrease the rate of cooling and maintain the set-point.

It is important to note that devices like this require periodic maintenance, such as frequent replacement of the coolant for example. If the coolant is not changed frequently it can contaminate and in turn cause contamination of the laser itself resulting in a catastrophic failure.

Well designed water-cooled laser cutters will also incorporate a flow sensor so that the laser cannot be accidentally operated when the cooling unit is not powered-on or should the cooling unit fail.

I cannot emphasis enough just how important it is to effectively cool the laser source as significant variance in thermal load to the laser is the single biggest cause of premature laser failures.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions and we have installed machines all over the World to the widest range of environments. Our experts would be happy to advise you on this or any other aspect of your laser system installation.

Choosing the Correct Focal Length of a Lens for a Laser Cutter

In a previous article we explained the types of lens that can be used in a laser cutting machine. The most common lens type used in a low power (<100w) laser cutter is the Plano convex lens.

These lenses are available in a variety of focal lengths to provide for a range of varying beam profiles and focal point sizes. When laser cutting sheet materials many people get confused about which focal length of lens to use.

A short focal length lens, like 1.5” for example, provides for a very wide beam profile with a very small focal point to deliver maximum energy density. For laser cutting applications this lens is best used for thin materials such as laser cutting paper, laser cutting card and laser cutting wood veneer because the smaller focal point provides for minimal kerf; kerf is the width of the cut.

When thin materials retain heat they are susceptible to warping, which causes a defocus leading to deteriorated output quality and material waste. The smaller focal point of the 1.5” lens delivers less heat into the edge of thin materials so the 1.5” lens can help to minimise warping.

A long focal length lens, such as one with a 4” focal length, provides for a narrower beam profile but a larger focal point. When laser cutting thick materials the profile of the beam is the most important factor because a narrower profile will be more consistent in width as it passes through a material of greater thickness.

As a very rough guide, you can use a simple formula to choose the appropriate lens for the thickness of material you want to cut as follows:

Focal length of lens in inches x n = max material thickness in mm where n is 2 for the shortest focal length and for each lens thereafter is n+1.

For example:

A lens with focal length 1.5” x2 = Change to a longer focal length after the material is 3mm thickness

A lens with focal length 2” x3 = Change to a longer focal length after the material is 6mm thickness

A lens with focal length 2.5” x4 = Change to a longer focal length after the material is 10mm thickness

A lens with focal length 4” x5 = Change to a longer focal length after the material is 20mm thickness

No matter what the lens used, considerations with regard to available maximum power and the wave guiding properties of the material must be considered too. For example, it’s generally not viable to use a 4” focal length lens with a 10w laser.

At Lotus Laser Systems we manufacture a wide range of laser cutting, laser marking and laser engraving solutions. We pride ourselves on the quality and depth of knowledge of our support staff. Our experts would be happy to advise you on this or any other aspect of your laser system operation.

Preventing Fires in a Laser Cutting Machine

Some suppliers include warning devices within their laser cutting machines designed to indicate the presence of a fire and would have you believe that material flaming during laser cutting of potentially flammable materials, such as laser cutting acrylic, laser cutting wood or laser cutting card is a normal part of the process.

Nothing could be further from the truth.

Allowing the material to flame is at best an incorrect use of a laser cutting machine and at worst a very dangerous risk of causing a major fire. Flaming during the laser cutting process will damage the material as well as deteriorate the system optical components leading to wasted time, wasted materials and expensive repairs.

Allowing the flaming to develop into igniting the material is extremely dangerous and nothing short of user negligence.

If the material is flaming it indicates a serious fault in the process that could relate to a misguided use of the equipment (incorrectly specified machine and/or inappropriately trained operator), incorrect parameters being used, incorrect focus or optical configuration (lens) and a variety of other common user errors.

In most cases flaming during laser cutting can be related to two specific causes:

1) An inadequate rate of laser fume extraction and/or air assist. If the vapours generated during the laser cutting process are not quickly and effectively removed from the path of the laser beam they can combust. In vapour form the material will ignite much easier than it will as a solid.

The best way to remove these fumes is by way of aggressive extraction from the underside of the material combined with a targeted delivery of high pressure through a small bore nosecone. This keeps the vapours away from the cutting point, preventing flaming.

2) An inappropriate use of the laser cutting machine. Some suppliers would have you believe that it is perfectly safe for a 30w laser to cut 20mm thickness acrylic. Just because the machine can do such a thing doesn’t mean it should. Using a laser of very low power to cut thick materials requires a very slow feed rate and sometimes multiple passes.

Also, using a lens with a short focal length (anything less than 127mm or 5” f/l) to cut thick material (>12mm or ½”) means that even for waveguide materials, such as acrylic, the majority of the material is being cut with a beam significantly out of focus. This maximises the heat absorbed by the edge of the material and in so doing brings closer the flash-point where the material ignites.

It is therefore more important that when using a lower power laser to cut thicker material, the user is even more vigilant with their supervision of the process.

Whenever the machine is laser cutting, no matter what the materials are in terms of type or thickness, the laser cutting machine should NEVER be left unattended for more than a few moments at most. We train operators to have a constant ‘line of sight’ to the machine at all times that it is laser cutting. In the event that flaming appears the process must be stopped and the system configuration and/or parameters adjusted accordingly. In the event that flaming still occurs our advice is not to continue with the process. If the user has no option but to continue while the material is flaming then we advise to do so with a great degree of caution and a real understanding of the risks being taken.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions and we pride ourselves on the quality and depth of knowledge of our support staff. Our experts would be happy to advise you on this or any other aspect of your laser system operation.

Control Options for Efficient Use of a Laser Cutter

Although there are now a large number of suppliers of laser cutting machines there are primarily just two design principles of how to control the machine.

Some manufacturers prefer to use an on-board user interface with a buffer to which the user downloads a file via some kind of graphics or CAD package through a print driver. The user then selects the file to run via the laser cutting machine user interface. This type of control for a laser cutter has a limited level of functionality and will have a finite buffer file storage capacity, so there is a limit to the number/size of files that can be downloaded to it. Another downside of using this design is that the commonly used buttons, such as START for example, will wear-out at which point the whole panel needs changing, which for some machines can be an expensive part swap.

An alternative way to control the laser cutter is directly from a PC. This kind of control is more like the advanced CAD/CAM interface found on high-end CNC machines with the most functionality and virtually no limit to the size/complexity of the job file. However it can be more risky to control the laser cutter like this if during production the skill or experience of the user is limited or even, for example, for security reasons the operator is not allowed access to the PC. Controlling the laser cutting machine in this way can also be more time consuming, especially if the system is of a larger format and the PC is some distance away from the main laser cutting area.

Some laser cutting machines offer a combination of both of the above options so that the operator can select the method that is best suited to the skill of the operator and the application at hand.

Sometimes the operator can use the two methods for one job. For example, during initial set-up a skilled operator will use the enhanced CAD/CAM functionality of controlling the laser cutter from the PC but at the point where production starts and possibly another lower skilled worker is used for the labour, the operator can download the file to the laser cutting machine so that that all the operator has to do is to handle the materials and press the START button on the machine interface.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions. All of our laser cutting machines incorporate both of the control methods described above. Our experts would be happy to advise you on this or any other aspect of how best to configure a laser cutter for your application.

7 Tips to Buying a Laser Engraving Machine

1) Focus on the core application: laser engraving or laser cutting It is easy to be allured by how many other applications a machine can perform. A good all-rounder is a compromise machine in almost every aspect. Just because a machine can cut as well as engrave doesn't mean it can do both functions very well. Machines designed for a specific purpose will always perform the core application better so it should be no surprise that a laser cutter will cut better than a laser engraver and vice versa.

2) Throughput (how many parts produced per hour) is almost always the key to commercial success. Speed of production is of paramount importance even if right now your business volume is low. Higher throughput will deliver the opportunity to lower your sales price while simultaneously increasing your margin and you can deliver faster too. These three elements are the key to competitiveness, winning and growing your laser engraving business.

3) Consider carefully the true cost of ownership as this has a huge impact on profit erosion. Nobody intends to buy a laser engraving machine to use for just a year and then throw it away. To most this is a long term investment but the majority of buyers focus primarily on the purchase price. The real cost of a machine should be judged by the cost of ownership over its entire working lifetime, which for a good machine will be approximately 10 years. Commonly, cheap machines cost far more to own by way of replacement parts, excessive maintenance and lower output quality/productivity. The best indicator for a high cost of ownership is a machine built with consumable components so be wary of sales hype such as 'easy to change' or 'cheap to fix'.

4) Consider the technology first then consider the brand. We often see whole workshops installed with rows of the same laser engraving machines where the buyer has made purchases based on 'we always by brand X'. If a brand can supply the right machine for the job then brand loyalty certainly has many advantages, however, performance of the technology should be a bigger priority.

If we all stuck to brand only purchases then we'd all be using Nokia or Motorola phones today. It's often newer and sometimes smaller companies that deliver innovation simply because they have to in order to enter a market or even to survive so before you buy, take a good look at what else is available from the lower profile brands before you consider buying what you are used to. A look beyond page #1 of Google can save you a small fortune.

5) Buy from a well established, reputable supplier that has knowledge of applications as well as the kit they are selling.

You would expect most providers of machinery to understand the product they are selling but this should never be taken for granted. Before buying push the salesperson to test their knowledge of the product, how it functions and especially their knowledge of applications. Don't settle for a preset demo that's been tried/tested by the manufacturer.

If the salesperson does not understand your application how can they recommend to you an appropriate system configuration? Remember that many sales people will try to sell you what they want to sell rather than what you should be buying. It is unfortunately all too common that we see companies using the wrong tool for the job because they were misinformed.

6) Look carefully at warranty and support guarantees.

Despite the hype, especially on the Internet, the only guarantee that you can rely upon is that nothing lasts forever: all machines will fail at some point. The more successful you are then the harder your laser engraving machine will work and the more likely it is that it will suffer a fault. If you are fortunate enough to be successful there is never a good time to have a machine down.

When a failure occurs you want to know how quickly it can be fixed and what the overall cost will be so look carefully at the small-print of system warranties and look even more carefully at the support resources of the supplier. If you can, talk to a support technician or two as well as the salesperson as these types of people often speak very differently about the same product.

7) Remember the core fundaments to a good system design is a careful balance of Functionality, Affordability, Reliability.

A system that is more functional is often by default less affordable and can actually be less reliable. A system that is more affordable is by default less functional and can also be less reliable. Logically, an average machine will be a happy medium of all of these things but an average machine will most likely deliver no more than average results.

It's therefore of vital importance to 'buy right' and choose a system that can deliver to the demands of today with a percentage of ability to cover some of the demands of tomorrow.

This consideration is not just about laser power, laser marking speed, etc but is also about software capabilities too. Today you may need to mark text and logo but tomorrow you may need to laser mark barcodes, for example.

Don't buy a Ferrari if you have 3 kids to take to school and don't by a Nissan Micra if you want to race along the German Autobahn. If you need to do both then in this analogy you actually need two different machines. The same is often true for a good laser engraving workshop.