How To Choose A Laser Cutter

05 Mar How To Choose A Laser Cutter

With so many types of laser cutters out there, choosing the right laser engraving and cutting machine can be a daunting experience with plenty of pitfalls along the way.

Steve Cockerham, Managing Director at HPC Laser, takes an honest and practical look at some of the most common questions customers have when purchasing their first laser cutter.

Material Compatibility: What Can & Can’t You Cut

CO2 laser engraving and cutting machines are capable of processing a very wide range of non-metal materials and will produce excellent engraving results on metals that have been anodized, powder coated, or painted.

A CO2 laser engraver will not engrave directly onto uncoated metals such as steel, stainless steel, brass or aluminium.

However, a ceramic marking compound such as Thermark or Cermark can be painted or sprayed on the metal first, allowed to dry, and then engraved with a minimum tube power of 50W which burns the marking compound into the surface of the material.

The unused marking compound is then washed from the workpiece with clean water to produce a nice clear engraving on the parent metal. Marking compounds are available in various colours but can be very expensive.

If you are looking to engrave large volumes of uncoated metal components, then you may want to consider a fiber laser engraving machine which is much faster than a CO2 machine and, because of the fibre laser wavelength, will engrave onto uncoated metals directly without the use of a marking compound.

Cutting a Variety Of Materials: Plastics, Wood, Paper & Leather

The most common materials that can be cut using a CO2 laser include plastics, with acrylics being particularly popular and versatile.

Excellent results can be achieved on clear acrylic, with the heat and speed of a CO2 laser machine producing excellent, polished edges without any additional processing such as flame polishing required.

Great care should be taken to ensure that any plastics that are processed do not contain harmful materials that would be released during processing.

Typical examples include PVC or any other plastics which contain chlorine. These materials can release harmful products when heated – such as sulphuric acid – which will present a health hazard and also attack your laser machine.

Some plastics cannot be effectively processed on a CO2 laser machine, often because of the heat-resistant characteristics of the material.

These include ABS and polycarbonate, both of which a CO2 laser machine will cut and engrave but not to the same thickness or quality of results as acrylics. Processing of acrylics produces different results depending on the manufacturing method.

Cast acrylic cuts very well and produces a nice contrast when laser engraved, such as a white engraving on clear and coloured acrylics. Note that extruded acrylic can crack easily when cut, especially on sharp corners, and an attractive contrast is not always possible when the material is engraved.

Other Materials

Woods, including solid wood, plywood, MDF, paper, card, and leather, are also very common target materials, although the thickness and specific nature of material will dictate the power and type of laser cutter you need.

Cutting Paper & Card/Cardboard

Some of the most impressive materials that can be processed include paper and card.

This is not only because of the very impressive speed that the machine can operate at on these materials but also how intricate designs can be achieved with almost no burning of the cut edges.

Delicate lace designs can be produced at incredible speeds and it is capabilities such as this that make laser machines very popular for personalised products such as wedding invitations and greeting cards.

Cutting & Engraving Wood

Woods can vary significantly in their ability to be laser engraved and cut, primarily because they are a natural product and a single piece of wood can be inconsistent right the way across a single piece of material.

Knots and grain can make wood more difficult to engrave and cut in some areas, as grains react slightly differently to the heating effect of the laser, sometimes producing colour variations or stripes when engraved.

Plywood is a popular option for laser processing, but some plywoods such as poplar and birch are more laser-compatible than others. However, these materials still contain some inconsistency and natural variations such as grains and knots.

Plywood manufacturing processes also involve glues and can sometimes involve fillers to improve the quality of the finished product. Thin plywood can twist and warp in storage due to variations in humidity, temperature and many other factors.

This variation in the height of the material when placed on the laser bed can lead to cutting and engraving inconsistencies because the laser cannot remain correctly focused on a workpiece that isn’t flat.

Cutting & Engraving Leather

Laser machines can produce excellent cutting and engraving results on leather, but the results can vary depending on the exact type of leather and the tanning method used.

As with many other materials, it’s best to test and fine-tune the machine settings on a small piece of the material before attempting to process a full-sized piece.

It’s also good practice to assume that one piece of leather will require different settings to another piece because of the natural variation in material and tanning process.

Some Other Ideas…

Some customers have used our machines to good effect to engrave some more unusual materials including foodstuffs such as macaroons, breadcakes, pasta, pumpkins, fruit, and even to cut a pizza into equal slices!

Main Considerations When Buying A Laser Cutter

Below we run through all the various important considerations you need to make when buying a CO2 laser cutter, from laser tube type and power, to cooling and air assist.

Understanding Laser Tubes

CO2 laser cutter tubes are a very affordable alternative to the much more expensive metal DC RF tubes which are expensive to buy and can be very expensive to refurbish when the laser tube has expired.

Water-cooled, CO2-filled, glass laser tubes are reliable, durable, and flexible in their ability to engrave and cut a wide range of materials.

Furthermore, when the laser tube expires, they are very cheap to replace with a new tube and made from almost completely from recyclable materials.

Understanding Laser Power (Watts)

Laser power can be one of the most confusing aspects of machine selection but is actually relatively straightforward.

More power usually means the ability to cut thicker materials or the same materials faster. Larger machines tend to be offered with larger power tubes and many machines can be installed with several laser power options.

Essentially it depends on what you want to engrave and cut and how fast.

We recommend a maximum power of 80W for a nice balance of engraving and cutting. More powerful laser tubes are difficult to control at low powers, in addition to generally having a larger spot size, and therefore produce less consistent results when engraving.

We recommend that laser tubes above 80W be used only for cutting.

Laser tube powers are rated in 2 different ways – nominal and peak power.

• Nominal power is the maximum power that the tube is capable of delivering on a continual basis.
• Peak power is the maximum power that the tube is capable of delivering during its expected lifetime.

Some suppliers will rate their machine on the higher peak power but HPC prefers the option of transparency and rates their machines and tubes on the lower nominal rating.

Typical cutting capabilities by laser power are illustrated by the table below. However, it should be noted that glass laser tubes are handmade, have some natural variation in the manufacturing process, and therefore not all laser tubes of the same power and design perform the same:

Water Cooling & Your Options

CO2 laser engraving and cutting machines always require a source of water to keep the tube cool and prevent it from overheating.

There are 2 main methods to achieve this, a water tank and submersible pump or water chiller unit, understanding your requirements will help you make the right choice.

Water Tank Cooling

HPC supplies a 35-litre plastic water tank and pump for all machines below 80W unless the customer chooses to purchase a water chiller.

The tank is filled with water, the pump is placed in the bottom of the tank, and hoses are attached to the inlet and outlet ports on the laser machine.

The submersible pump is fitted with a regular 3-pin 13A UK plug and can be plugged into the back of the laser machine. When the laser machine is switched on, the submersible pump then starts automatically.

As the machine is used, the temperature of the water will gradually increase and use of the laser must stop immediately if the temperature of the water reaches 25°C otherwise the laser tube can be permanently damaged.

Water Chiller Cooling

A good quality water chiller contains a refrigerant gas, compressor, and pump, rather like the active components of a refrigerator.

Circulating water in the chiller is passed across cooling coils which actively chills the water and maintains a constant temperature, typically around 20°.

The main benefits of a water chiller are that the laser machine can be operated continually if required, with no need to monitor the water temperature.

Good chillers, such as HPC Lasers CW5200 or CW400 are capable of cooling a tube up to 150W in power and will produce an audible and visual alarm if the water temperature is too high or too low.

HPC Laser does not recommend the use of the CW3000 cooler for CO2 laser cutters as it is a simple radiator/fan arrangement and doesn’t contain the refrigerant gas and compressor required to actively chill the water.

What Type Of Water To Use?

Regardless of the method of water cooling chosen, HPC recommends the use of distilled or de-ionized water rather than tap water due to their ability to better restrict the formation and growth of bacteria and other impurities.

These can block water cooling components and passages if left unchecked hence regular water changes are required to keep your machine in good working order.

Important: Another key consideration concerning water cooling is the care required to prevent the water from freezing during cold weather.

Water expands as it freezes and so if the laser tube is full of water when it freezes the expansion causes the glass laser tube to crack and the tube will then need to be replaced with a new one.

Depending on where the tube cracks, it’s possible that the water can also flood the machine and cause damage to the electrical components.

Freezing of the water is an expensive situation but simple and inexpensive preventative measures can be easily applied.

Side note: All HPC laser machines are installed with water flow switches which prevent the laser from firing if insufficient water flow is present or the water hoses are attached to the laser machine the wrong way round.

Fume Extraction & Why It’s Important

Engraving and cutting all materials using a laser produces fumes that need to be extracted from the machine and exhausted from the local area to prevent potential health issues.

HPC laser offers 2 main options to address this issue:

A Fume Extraction Fan & Flexible Hosing

The fan is housed in a convenient protective steel enclosure and has an inlet and an outlet port. The inlet port is connected up the rear of the laser machine and the outlet port is routed to the outside of the building, ideally through a hole in the wall or roof.

The fan is installed with a regular 3-pin 13A UK plug and can be plugged into the back of the laser machine similarly to the water cooling and compressor so that the fan immediately begins to work when the laser machine is switched on.

Self-Contained Fume Filter Machines

If access through an outside wall or roof is not possible, such as in a school classroom, HPC Laser offer self-contained fume filter machines. These contain an extraction fan and usually 2 removable filter cartridges.

The HEPA pre-filter removes dust from the fumes extracted from the machine and then the activated charcoal or combined filter removes the smell from the fumes. The machine then exhausts cleaned air back into the room.

Pre and combined filters need to be replaced periodically for the machine to provide consistent results.

Materials with a high dust content such as plywood will saturate the pre-filter before the charcoal filter, whilst materials with a low dust content but high aromatics content such as acrylics will saturate the charcoal filter before the pre-filter.

It’s extremely difficult to offer information as to how long filter cartridges will last as their life depends largely upon the bed size of the machine, the material being processed and for how long.

It is also important to ensure that a fume filter is appropriately sized to ensure the filter cartridges do not saturate prematurely.

Fume filters are a relatively expensive solution but provide an excellent option when external ventilation is not possible.

Air Assist: Why Do You Need It?

Compressed air needs to be delivered to the cutting nozzle of a CO2 laser machine. This is to blow smoke and heat away from the nozzle and prevent damage to the focus lens.

HPC Laser provides a small diaphragm compressor with all their CO2 machines.

The air hose from the compressor is connected to a quick-release fitting on the back of the laser machine and the compressor then plugs into an electrical socket on the back of the laser machine so that it starts when the laser machine is turned on.

Not only is an effective air assist function essential on a CO2 laser machine for the reasons described above, air delivery to the cutting nozzle helps the laser beam to produce good quality cuts, and also helps to minimize the burning and flaming of some materials during cutting.

Laser Optics: How Do They Work?

Lasers work similarly to how the sun’s rays can be focussed and intensified using a magnifying glass.

CO2 laser engraving and cutting machines work by passing this invisible laser beam of typically 6-7mm diameter across a series of mirrors and through a focusing lens.

This reduces the beam diameter down to only microns at the correct focal height (usually around 50mm from workpiece to lens) which increases the intensity of the beam sufficiently to provide the engraving and cutting capabilities of the machine.

Once the unfocussed beam has passed through the lens it begins to diverge at the same rate at which it was focussed. Hence at 50mm below the focal point, the beam returns to its original 6-7mm. As the beam continues to diverge further away from the lens, it continues to grow and weaken and is scattered around the machine cabinet.

This scattered beam is then absorbed by the coated metal surfaces of the machine.

Because of the relative ease with which the focussed beam weakens and becomes harmless, it is the unfocussed beam that is considered the more hazardous of the two, particularly due to its ability to travel long distances whilst losing only a small proportion of its power.

Most machines have a series of 3 x mirrors to direct the laser beam into the cutting head. These mirrors are intended to be mounted at 45 degrees so that the beam is reflected at right angles. Each mirror mount has some adjustment screws which can finely tune the mirror angle so that the beam is traveling consistently across all 4 corners of the machine bed.

Periodic adjustment of these screws by the machine operator is necessary to keep the machine performing at its best. Adjustment of mirror alignment is not especially difficult but it does need to be carried out in a clear and organized manner.

Mirror alignment is a critical skill of laser machine ownership and day-to-day running, and gets easier with experience.

Because of the well documented issues owners experience with auto focus systems, HPC machines use a manual focusing method on their machines whereby a tab on the lens tube is set to the height of a focus tool by raising or lowering the worktable.

3 Reasons HPC Doesn’t Use Autofocus Systems

• Autofocus systems include moving parts such as springs and probes which can become clogged with debris and sticky deposits. Unless these parts are kept very clean, they can jam and provide false readings and can even lock the bed in upward travel, potentially damaging the bed, focus probe and transmission components.
• Focus probes are easily damaged by driving into workpieces.
• Sometimes it’s useful to be able to produce work slightly out of focus or to focus mid-point on a curved surface such as a hip flask. It’s much more difficult to do this on a machine equipped with auto-focus.

Cleaning Your Mirrors & Optic Lens

Cleanliness of machine optics is a very important aspect of machine ownership. During cutting and engraving, smoke and debris are released which can settle on the machine mirrors and lens.

If the machine is used with these deposits on the optics, the laser can burn them into the surface of the optic. This can produce a cumulative effect, with heat build-up further increasing damage to the mirror or lens, and in some cases the optical device can crack or shatter.

Cleaning of the optics is the best course of action to prevent such instances.

All mirrors and the lens should be cleaned regularly by wiping isopropanol alcohol across the optics with a good-quality cotton bud.

Any optical devices that cannot be cleaned should be replaced.

Controllers & Software: The Brains

The software that you can use to control your machine depends upon the controller, or motherboard, that you have installed in your machine.

The original generation of HPC Laser machines were installed with a Leetro controller which was compatible with Lasercut software.

The latest generation of HPC machines are installed with Ruida controllers which are compatible with RD Works and Lightburn software.

Lightburn is widely regarded as the best laser machine control software available and has a wide range of design and creative functions as well as the capability to communicate directly with the laser machine.

Some customers will design in an external design program such as Adobe Illustrator, Corel Draw, Autocad, Inkscape or 2D Design. In such cases, the design file is usually saved as a compatible file type, such as a .dxf file, and then imported into the laser machine software.

However, Lightburn includes the capability to open a wide range of design files directly, such as .ai, .svg, and .pdf.

Understanding Laser Classification & Safety

Laser classification is a key factor in machine safety.

Class 4 laser machines are usually either completely open or manufactured without safety switches which should prevent the laser from firing when the lid or other cabinet panels are open.

Direct access to the laser beam is possible with such devices and a badly adjusted mirror can even lead to the laser beam exiting the machine cabinet, potentially setting fire to items in the room or even causing eye damage if it were to strike someone in the eye.

For this reason, class 4 machines are forbidden in an educational environment. Laser safety glasses should ALWAYS be used with class 4 laser machines, with the lenses filtering out any harmful laser radiation if the laser beam strikes them.

However, it is critically important that laser safety glasses with the correct wavelength protection are chosen. For CO2 laser engraving and cutting machines, HPC Laser recommends laser safety glasses with a protective wavelength of 10.64µm.

Class 1 laser machines have a protective enclosure, usually painted or powder-coated steel. They include safety switches on panels that could be opened to gain access to the laser radiation such as the machine lid.

The laser beam should not be allowed to fire when any panels installed with safety switches are open. The latest generation of HPC Laser CO2 machines are installed with safety switches on the machine lid, laser tube access door, and debris recovery drawers.

This generation of machines is installed with CE-marked Allen Bradley Guardmaster safety switches with LED status lights to indicate when the switches are registering as being open or closed.

Fire Safety & Maintenance: How To Stay Safe

Because flammable materials are often processed on a CO2 laser engraving and cutting machine, fire is one of the main hazards, but is easily mitigated through attention to a few simple principles:

• Firstly, and most importantly, never EVER leave your machine unattended whilst operating. Small flames might break out during the processing of some materials, especially during the cutting of complex designs in wood, acrylic, and other plastics. If a small flame breaks out whilst processing your material, simply press pause on the machine keypad and then resume once the flame is extinguished. If you need to leave the machine for any reason, pause operation and resume when you return.
• HPC machines are fitted with a keyed lock to turn the machine on. Ensure that only suitably trained and competent personnel have access to the keys and that they supervise other personnel at all times.
• Regular maintenance practices. Clean your machine regularly. Flammable oils and other products can accumulate on your machine bed so clean it regularly. Dettol-type floor wipes work well. Make sure all material offcuts are removed from the machine on a regular basis. Click here for a complete guide on laser cutter maintenance.
• Avoid duplicate lines in your design that cause the laser to pass over the same part of the material more than once. This has the potential to heat or even ignite any material offcuts that are present underneath the machine bed.
• Always have a good quality fire extinguisher close to hand. Remember that your laser machine is an electrical device so a CO2, Halon or other compatible extinguisher should be used. Do not place your extinguisher in a location that would be difficult or impossible to reach in the event of a fire.
• Use your machine supplier’s recommended settings depending on the materials being processed. Excessive heat build-up from high power or slow speeds can cause ignition of the material, especially in thick plastics such as acrylics.
• Keep your air assist and fume extraction in good working order. Inadequate air delivery to the cutting nozzle can cause some materials to “flare” and significantly increase the risk of a fire. If in doubt, stop work and check adequate air delivery from the compressor to the nozzle.

Summing Up

Well, we hope that this guide has taught you everything involved with buying, operating, and maintaining a CO2 laser cutter.

As always, our team is on call 5 days a week to help guide you to a machine that is suitable for your needs, so please feel free to call us on 01422 310800 or email us at sales@hpclaser.co.uk.