The Importance Of A Good Environment For A Laser Cutter

The environment where you operate your laser cutter or laser engraver has a fundamental influence on the efficiency, reliability and long-term working life of the machine and its components.

All lasers generate heat as a by-product of the process inefficiencies so the room temperature is of a major concern. over heating can cause a catastrophic and somewhat expensive failure of the laser. The effective removal and control of this heat is key to prolonged and reliable use. All lasers will have an inbuilt cooling mechanism by way of fans (air-cooling) or some kind of chiller unit (water-cooling).

Most people understand this, however, an often overlooked aspect to temperature is how cold the environment gets, especially when the laser cutter is not in use. Even in the hottest of countries the temperature can fall to below freezing overnight.

During weekends and other non-working days, some environments are not temperature controlled so the temperature can fall/rise to abnormal levels. Extremes of temperature will cause many elements within the machine to expand and contract. This is particularly bad for RF lasers manufactured from metal.

Humidity is another influencing factor. High humidity, especially when combined with rapid changes in temperature, can cause condensation to form on sensitive electronics components, in turn causing those components to short-circuit.

An ideal ambient temperature for the room is between 15-30c. Rapid changes in room temperature can also cause adverse reactions. For these reasons we see spikes in support calls after times of long public holidays, such as Christmas for example.

TDusty and oily environments are not suitable to site a laser cutting machine because a build-up of dust/oil can cause components to overheat, moving parts can seize-up and optical components can fail through external contamination

Laser cutting machines should not be placed near to any source of heat/cold/air such as radiators, fans or air conditioning units and they must not be placed near to south facing windows where solar gain may cause overheating issues.

As with any form of electrical device a laser cutter must be protected from water and any form of moisture as well as unstable power supplies.

Some workshops incorporate machines that generate significant vibration, which can cause optical elements in the laser cutter to misalign

The floor type is often overlooked as a potential influencing factor. All laser cutters should be placed on a flat and stable floor. As the machine becomes larger and heavier this is more of an issue. Mezzanine and other flexible types of floor are not suitable as they can cause the system frame to twist in turn causing the motion system to bind.

If the environment is industrial and the above factors cannot be mitigated consider building a room within it where the laser can be isolated from the potentially harmful factors of the main factory area

As a general rule of thumb, the best environment to place your laser cutter is one where you are comfortable to work while wearing normal, office style clothing.

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.

The Effective Use And Maintenance Of Lamella Bars In A Laser Cutting Machine

For most applications where you are laser cutting sheet materials, such as laser cutting acrylic or laser cutting wood, by far the best form of cutting table is one that incorporates lamella bars.

Lamella bars are stronger and more resilient than other forms of cutting table and we’ve written other articles to explain this in detail. With this article we shall overview the best way to use and maintain your laser cutting machine lamella table.

One of the main benefits of a lamella bar cutting table is the way in which it deflects any laser power that passes totally through the material away from the underside of the material. This prevents adverse material reaction and minimises the risk of flaming

If the machine is fitted with an underside extraction design the larger spacing of lamella bars also provides for greater efficiency of laser fume extraction.

The surface edge of each bar supports the weight of the material. These bars are very strong and will not deform under the heaviest of materials being placed inside the laser cutter.

Depending on the job at hand, it’s often desirable to remove as many of the bars as possible so that the overall surface area of the bars holding the material is minimised. This further increases the cutting quality and extraction efficiency.

Judge carefully how many mars to remove. Too few bars and the material may deform. Also, it’s important to consider how the cut parts will fall through the gaps in the bars. Spacing bars that allow materials to kink upwards but not fall through completely must be avoided, especially where the laser cutter is fitted with a nosecone moving close to the surface of the material as kinked/traps parts may collide with the nosecone

High debris applications, such as laser cutting wood and laser cutting card will contaminate the cutting table faster and to a greater degree. Unlike other forms of laser cutting table lamellas are not consumable items and can be cleaned. We recommend setting aside a small number of bars that can be in the cleaning process while others are being used in the laser cutter.

Lamella bars can be cleaned by simply wiping them down with a light detergent. If they are highly contaminated then they can be soaked overnight in a weak mixture of light detergent and water. Be careful not to use a corrosive cleaning agent as the bars will be made from aluminium and when old some of the protective anodised layer will be removed

In the UK we have the brand products Cilit Bang and Mr Muscle. Both brands make products for degreasing, usually labelled as a kitchen cleaner, and these are good for cleaning lamella bars in a laser cutter.

Spray each bar directly with the cleaner. Allow it to sit for 1-2hrs. Dilute 1 part cleaner to 20 parts water and use a decorator’s plastic wallpaper tray to hold enough solution to cover the bars. Place the pre-soaked bars in the tray and leave overnight to soak. In the morning, remove the bars and wipe down with a clean, wet cloth. Usually, the bars will then look as new.

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 maintenance.

Contaminated Optics within a Laser Cutter

Some of the most important components of a laser cutter are the optical elements. These are components that either deflect the beam (mirror) or allow the beam to pass through (lens).

Even when completely new, all optical components will cause some degree of attenuation: in other words, remove a small amount of laser power. Therefore, especially when the design of a laser cutter incorporates a large number of optical elements the laser power that arrives at the lens is less than the power that emits from the laser source.

Contamination of the optical elements of a laser cutting machine causes further attenuation and if left unchecked can have a massive detrimental effect on cutting speeds and in turn production efficiency.

Attenuation is more of an issue where the laser cutting machine incorporates a laser source of a lower power.

For example, if a laser cutter outputting 30w incorporates four mirrors, a combining optic for a positional diode and finally the lens, then if each element draws 2 watts of power the net attenuation is a 27% (almost 1/3rd) power loss.

Contaminated optics can often draw much more than 2w of laser power so it’s quite possible that a laser cutting machine <50w can be losing more than half its potential power simply through optical attenuation and/or contamination.

Laser optics will suffer accelerated contamination if the main application creates a high amount of debris; for example, laser cutting wood or laser cutting card. An ineffective or incorrectly specified exhaust system will further compound this problem

Low levels of contamination of laser optical elements can be easily cleaned, however, if the contamination is allowed to build-up too much it is often impossible to remove. At some point an over-contaminated optic will draw so much power that the heat generated will cause it to fail catastrophically.

For these reasons optical elements within a laser cutting machine are deemed consumable items so for users where the laser cutter is of strategic importance it’s a wise precaution for the user to hold stock of replacement optics.

Over-cleaning of optical elements can cause undesirable removal of the coatings, which is almost as bad as not cleaning them enough. As a general rule of thumb it is the frequency of checking for contamination that is more important and optics should only be cleaned if they show obvious signs of contamination.

With most system designs, optics that are closer to the focal point will contaminate faster than those that are closer to the laser source so, for example, inspection of the lens should be performed far more frequently than the first mirror.

We cover the cleaning of laser optics in another article.

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 maintenance.

Plano Convex Lenses for a CO2 Laser Cutter

In an earlier article we explained about the two main types of Zinc Selenide (ZnSe) lenses used within a laser cutting machine and that the most commonly used of these is a Plano (flat) Convex (curved outwards) lens

Aside from physical dimensions this type of lens has three defining characteristics:

1. Focal Length (F/L): the point from the lower (flat) surface to the point of beam convergence
2. Focal point: the point of beam convergence
3. Depth of focus: a range measured between a point above and below the focal point in which the lens delivers a desirable result.

The focal range is application specific and will vary depending on the material being processed and whether the application is laser cutting or laser engraving.

During manufacture, by variation of the convex surface the point of convergence can be shortened or lengthened and in turn the size of the focal point and depth of focus will vary too

As with photography, selecting a specific lens for certain applications can enhance significantly the output quality; for example, a close-up lens or a telephoto lens. The same is true for lenses within a laser cutting or laser engraving machine. 

Lenses in a laser cutter are interchangeable.

By increasing the focal length of the lens, the truncation of the beam becomes narrower and the focal point becomes larger. This is particularly useful for laser cutting through materials of a greater thickness or for laser engraving surfaces that are not uniformly flat because longer focal length lenses have a greater depth of focus.

Some manufacturers refer to long focal length lens as a 'cutting lens' and a short focal length lens as an 'engraving lens'. Technically, this is not accurate.

Longer focal length lenses are more useful when engraving high debris materials, such as wood for example, where the greater distance between the lens and the material provides for a lower risk of lens contamination.

Using a lens with a short focal length will have a very wide truncation with a very narrow depth of focus, so the uses for such a lens are very limited, however the resulting very small focal point provides for the highest possible resolution and also for maximum energy density of the laser; good for removing more material in a single pass. A good use for this type of lens would be marking photographic detail or engraving rubber stamps

The short focal length lens is commonly misunderstood as being only for laser engraving. Actually, it can also be useful for some laser cutting applications. For example, some materials are very heat sensitive and a lens with a very small focal point is less likely to draw heat away from the cutting point into the material causing adverse effects, such as material warping.

In a typical laser cutting or laser engraving machine the range of Plano Convex ZnSe lenses will be as follows:

1. 38.1mm (1.5”) F/L: high resolution engraving, <1mm material thickness cutting
2. 50.2mm (2”) F/L: good resolution engraving, <5mmmaterial thickness cutting – this is the best 'all-round' or 'general purpose' lens
3. 63.5mm (2.5”) F/L: lower resolution engraving, 3-10mm material cutting
4. 101.6mm (4”) F/L: low resolution engraving, 10-20mm material cutting

Lenses of longer focal length are available but only used for cutting and will not generally be suitable for smaller format machines.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions with a variety of lens options. Our experts would be happy to advise you which configuration would suit your application best.

Types of Air Assist for a Laser Cutter

Most laser cutting machines will incorporate some form of air or gas assist the function of which is three-fold:

• To improve the efficiency of the laser cutting process. Generally, this works by the positive air keeping vaporised debris away from the path of the beam in order that all of the laser energy is applied to the material.
• To improve the quality of output. This works by the positive air helping to keep vaporised debris away from the surface or the edge of the material being laser cut so that contamination of the material is minimal.
• To reduce the requirement for maintenance (cleaning) and prolongue the life of optical elements. This works by positively pressurising air at the focus carriage (the laser head) so that contaminants are kept off of the sensitive surfaces of the optical elements.

Well designed laser cutting machines will provide for all three of the above functions.

Some machines do not incorporate a nosecone. These are not good for laser cutting but are sometimes better for laser engraving because without the nosecone the laser head is lighter in weight, so it can move faster with lower vibration. If these machines have air assist then it’s usually delivered via a small bent metal tube delivered at an angle to the work surface at the focal point. The angled air assist helps to dislodge debris, pushing it into the flow of the extraction across the material surface.

It’s important to note that unless the laser fume extraction is very well specified then this type of directional air assist can cause premature contamination of the lens. At Lotus we do not favour this design of air assist.

For best results when laser cutting the laser head will incorporate a nosecone, which will sit a few millimetres away from the surface of the material. At the end of the nosecone will be a small hole through which both the beam and air assist are delivered. If the bore of the hole is too big and/or the distance of the nosecone from the material is too great then the whole process of air assist becomes very inefficient.

Nosecones with smaller holes work better as they direct the air more locally through the cut instead of around the cut. The smaller hole also helps to increase air pressure and allows for a smaller air pump to be used. In case where a gas is used instead of air, such as nitrogen for example, a small nosecone is essential to minimise the waste of a potentially expensive gas.

An often overlooked aspect to the design of air assist is the hose bore (diameter) through which the air flows from the pump to the nosecone. Many machines use a tube with a bore that is too small. This greatly reduces the volume of air that can flow through it.

Using a larger bore air assist delivery tube reduces the speed at which the motion system can run but greatly increases the efficiency of the air assist process. With some models of Lotus Laser Systems it’s common for customers that process high debris materials like laser cutting wood or laser cutting card for many hundreds of hours without the need to clean the optics. Conversely, many machines on the market with poor air assist designs will require almost daily cleaning of optical elements.

One important point to note is that when a nosecone is fitted air assist MUST always be used otherwise the process can work in reverse and the lens can quickly suffer contamination and even catastrophic failure.

Lastly, it is very important for the laser cutting machine to be able to activate the air assist through its control software.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions with a variety of air assist options. Our experts would be happy to advise you which configuration would suit your application best.

Efficient Extraction From a Laser Cutting Machine

Most people when evaluating which laser cutting machine to purchase perform a simple tick-box exercise listing the various functions and features as listed in the manufactures sales brochure. Few actually analyse those features in detail to see how well designed they are and even fewer test those features to see how well or efficient they work.

Inefficient laser fume extraction is very costly in terms of increased maintenance, decreased throughput, poor quality output (wasted materials) and reduced component life. Bad extraction will be hazardous to the health of the operator and is the biggest cause of flaming (fires) in Laser Cuttes.

One of the most misunderstood and overlooked aspects of a laser cutter is the efficiency of the laser fume extraction design. In the majority of plotter format machines, extraction is taken from a vent positioned at the rear of the worktable. This causes fumes to be drawn over the surface of the material.

This type of extraction is generally OK for laser engraving but not at all good for laser cutting because the rising fumes block the path of the beam, dropping laser efficiency. The direction of air can cause lightweight materials to move on the worktable and this design of extraction often allows contaminants to contact with the laser head. The platen used in almost all such machines will quickly contaminate, causing a restriction with air-flow.

Some of the larger format machines utilise extraction from the laser head by way of a long, flexi hose. Again, this only works for engraving but it has many inherent faults. Firstly, the hose contaminates fast, restricting flow and dropping efficiency and with constant flexing it will perforate over time. Because of the narrow hose diameter the vacuum pressure needs to be very high and the volume of air that can be taken in this way is very low. It’s therefore not possible to use an extract to atmosphere system with this type of local extraction. This type of extraction cannot be used when cutting small parts and/or lightweight materials as they can be pulled into the path of the beam by the air-flow.

By far the most efficient way to extract from a laser cutter is from underneath the material. We call this Underside Extraction or UE for short. This causes a vacuum underneath the material, which if the blower is strong enough can hold slightly warped materials flat to the work-table. This is especially useful for laser cutting paper, laser cutting leather or laser cutting textiles. When combined with a well designed air assisted nosecone UE will pull the laser fumes down through the cut line virtually eliminating any chance of those fumes contacting the laser head. This will often increase edge quality, especially for high debris cutting applications like laser cutting wood and reduces maintenance in some cases to near zero.

Well designed UE will provide for an even pressure and flow of air across the whole worktable so the best machines incorporate some kind of funnel underneath the worktable with the point of extraction placed centrally to the funnel.

The best laser cutting machines will incorporate dual extraction ports: one to draw over the material and another from the underside.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions and can supply a wide range of extraction solutions. Our experts would be happy to advise you which configuration would suit your application best.

Extract to Atmosphere for a Laser Cutter

In an earlier article we discussed two main types of laser fume extraction for a laser cutting machine one of which was laser fume filtration and the other Extract to Atmosphere (ETA). Here in this article we take a more detailed look at the correct design of an extract to atmosphere system.

This is a highly specialised subject. Most laser cutting machine and laser engraving machine suppliers as well as many fume extraction suppliers do not truly understand what is required to provide for an efficient, well performing extract to atmosphere set-up for a laser cutting machine.

By some standards ETA is merely a small turbine with enough flexi-hose to hang out of the nearest window. Nothing could be further from the truth or in fact nothing could be more inadequate and potentially dangerous than this type of set-up.

For an ETA system to perform well and most importantly for it to be safe, the contaminated air within the laser cutting machine must be quickly removed and expelled well beyond roof height where it will quickly dissipate into the atmosphere safely.

This requires moving very large volumes of air, a by-product of which is the generation of high levels of noise. This is the main reason why some sites, such as those in inner cities, simply are not suitable for ETA.

Start at the laser machine by connecting a 1m flexible hose from the extraction port to some kind of gate. The gate will be used to control flow as well as shut-off the machine from cold/damp air that may enter from outside when the system is not in use.

The type of flexible hose is critical; under no circumstances use cloth or foil types of flexi hose as these are designed for very low pressure extraction, such as tumble-dryers, and they will collapse and perforate.

The only type of flexi hose to use is made from PU, sometimes treated to be ant-static and with very strong reinforcing wires. Use a transparent version as you can then monitor the level of contamination and change it when necessary

After the gate the duct must be made from galvanised steel with at least 150mm diameter. At each join it must be riveted and sealed using a suitable mastic. This duct will widen to match the diameter of the fan inlet. From the fan it will be a constant diameter to match the fan outlet.

The fan MUST be positioned OUTSIDE of the building so that the duct from the laser cutter is under vacuum. This is safer because if the duct is compromised fumes will not escape from it into the work environment. If circumstances allow, site the fan on the floor as it will be easier to service.

The performance of the fan is critical to the efficiency of the machine and should be specified by a professional making careful calculations for the size of the laser machine and the length/design/resistance of the duct.

To reduce noise, just before and just after the fan fit a pair of attenuators. These act similar to the baffle box on a car exhaust.

Beyond the fan outlet attenuator the duct should run in a straight line upwards to a point 1m beyond the roof line or apex of the building. The duct should terminate with a jet cowl and NOT any other type of duct cap.

Careful consideration should be given to the discharge point to allow for maximum dissipation of the expelled air and minimal nuisance to neighbours.

This type of set-up will provide for many, many years of use with next to no deterioration in performance and little to no required maintenance.

At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions and can supply custom designed ETA solutions. Our experts would be happy to advise you which configuration would suit your application best.