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.