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.