Laser Cutting on a Lamella Table

In an earlier article we discussed two types of table used in a laser cutting machine one of which was a lamella table. Here in this article we take a more detailed look at this type of cutting table.

A lamella cutting table is essentially a series of thin bars laid on edge onto which the material to be laser cut is placed. These bars can be manufactured from sacrificial material such as acrylic or more commonly they are made from anodised aluminium.

If made from aluminium the shape of the bar is critical to its effectiveness. A well designed lamella will be shaped like an arrow head with a slightly rounded tip, which is the point where the material comes in to contact with the bar. Such a shape will deflect any laser beam that passes through the material away from the underside thereby minimising or even eliminating any backward reflection.

This is particularly useful for transparent materials such as laser cut clear acrylic, heat sensitive materials such as laser cut mirrored acrylic or materials that contaminate very easily because of the high amount of debris they produce, such as laser cutting wood.

A well designed laser cutting machine with a lamella table will allow for reasonably thick and therefore heavy sheet materials to be placed upon it without any distortion.

The best machines incorporate a design where the lamellas are easily removable. This allows for the removal of bars that are not required, reducing the surface area that the material is held by to a bare minimum and thereby creating a total void beneath the material.

Well made lamellas will last for many years and unlike the alternative, more commonly found honeycomb table, lamella bars can be cleaned, will not distort and so are not a consumable item. Should the bars ever require replacement then they can be replaced just a few at a time for a negligible cost.

For processing sheet materials like laser cutting acrylic or laser cutting plywood a lamella cutting table will produce results that far surpass that of any other form of cutting 

When combined with a well specified laser fume extraction system, especially when extraction is from the underside of the material, cleaning of the laser cutting machine will be massively reduced in frequency.

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

Laser Cutting on a Honeycomb Table

In an earlier article we discussed two types of table used in a laser cutting machine one of which was a Honeycomb table. Here in this article we take a more detailed look at this type of cutting table.

The honeycomb cell structure is made from what are essentially very thin strips of aluminium that are in some places glued together. This glued section is then extruded, concertina fashion, to form a sheet of honeycomb shaped cell structures.

This honeycomb material is actually designed to be laminated between two sheet materials, for example MDF, where it's used primarily in the construction industry. The resulting 'sandwich' board is very light weight and very strong, however, without this lamination the opposite is true; the honeycomb is incredibly weak.

The idea behind using this honeycomb is to minimise the occurrence of backward laser beam reflection; where the laser beam passes through the material into the honeycomb cell there is a void that allows the beam to pass well out of focus and so not reflect back into the material.

In some respect this works and a honeycomb table can be good for cutting non-rigid materials such as laser cutting textiles or when the requirement is to laser cut very small parts, however, because of the weakness of the structure it deteriorates very fast. It is also impossible to clean this type of table and problems occur when placing heavy materials upon it and/or when using extraction from below the material.

Therefore, this type of cutting table is truly a consumable item and frequent replacement can be costly over time.

Common faults with a honeycomb are that the aluminium sheet deforms, which actually can cause the very backward reflection that this type of table is trying to avoid. When processing heavy material, such as laser cutting acrylic, it can have a tendency to sag, casing for beam defocus. Once dirty it can cause debris to stick to new materials and using it with higher power CO2 lasers can actually cause the cell structure to separate.

Furthermore, there are limitations with regard to the overall size of a honeycomb cutting table.

In short using a honeycomb cutting table often has more limitations than benefits so unless it is your only available option or your application is one of the few where a honeycomb table works well it is far better to use a lamella type table when laser cutting sheet materials.

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

Cutting Tables For CO2 Plotter Lasers

For low power (<100w) CO2 cutting lasers one element of the machine that is often overlooked and misunderstood is the worktable.

The design and type of worktable can have a significant difference on the performance of the laser machine, the working life of its components and the quality of its output.

Most systems that are commonly available on the market today will consist of one or a combination of the following worktables:

• A stainless steel plate: This type of worktable is usually found in machines designed primarily as a laser engraver. For most laser cutting applications this type of table produces very undesirable results and requires significant maintenance (cleaning) even after the smallest of jobs.
• Honeycomb table: This type of worktable is manufactured from very thin aluminium that is glued and extruded to form a honeycomb structure onto which materials are cut. The design of this table is to minimise backward reflection and to allow hot gases and particulates to pass away from the underside of the material.
• Lamella table: This type of worktable incorporates thin bars that are usually made from anodised aluminium and indicates that the system has truly been designed as a laser cutting machine.

Most users would have had experience of a honeycomb table because this is the type of table supplied by most of the major EU and US laser machine manufacturers. Such tables are not very robust as the honeycomb material was never intended to be used in this way and will quickly deteriorate by way of bending and impact damage as well as contaminating very fast.

Therefore a honeycomb table is deemed a consumable item because it cannot be cleaned or repaired and with frequent use will require replacement in a number of months if it is to perform correctly. This is not a cheap item so it is therefore no wonder why equipment manufacturers like to incorporate this table in their machines!

It is however a good solution for laser cutting textiles and similar non-rigid materials.

For laser cutting acrylic, laser cutting wood and other rigid sheet materials a lamella table is a far more robust solution. In a good machine the lamella bars are very strong, allowing materials of a greater size/thickness/weight to be laser cut and the bars can be easily and quickly cleaned. It’s therefore common for these bars to last for several years of heavy use and replacement bars are often very low cost.

For best results when laser cutting rigid materials a high performance laser fume extraction unit should be combined with a lamella table as this combination delivers the ultimate solution in almost every aspect.

Why To Choose A Galvo Laser For Cutting

For some laser cutting applications the material is in a roll format. There are also circumstances where high levels of detail need to be cut very quickly to thin sheet materials, such as paper or card.

In such circumstances no other form of mechanical beam delivery is as fast as that delivered by a galvo beam deflection unit. Speed of cut is vital to the commercial viability of most jobs and in many cases if the cutting is very fast the material shows less adverse reaction to the heat.

For simple label cutting applications where the part is small (within 150x150mm) a standard set-up will likely suffice, however, where it is important to hold a smaller focal point and/or where it is required to mark beyond the work area of a conventional galvo machine a special design system is required and it is called a Dynamic Focus Galvo Laser (DFGL) or sometimes a 3d scanner.

Such a specialist machine incorporates an optical component in front of the XY beam deflection mirrors, which adjusts the convergence/divergence of the beam to provide for a consistent focal point over an area of up to 800x600mm.

These machines can cut materials held static (no part movement) or ‘on the fly’; where the material is continuously moving during the laser cutting process.

Examples of use would be for laser cut greeting cards, laser cut packaging or laser cut labels and other printed materials to name but a few.

With these machines the cutting speed is incredibly fast, often up to 10m/sec so it is required to use a laser source measured in several hundreds of watts; typically 200w or 400w.

While the purchase price of these kinds of laser can be perceived as being very high, often x2 to x3 the price of a typical plotter laser alternative, the production speeds can be x10, x20 or even faster.

By comparison, a decent galvo laser will often cut a job in mere seconds where an alternative plotter would take several minutes or more to perform the same task.

It is therefore in many cases far cheaper to use a single, higher performing galvo machine rather than a bank of plotter lasers as well as the fact that often, using a galvo laser is the only way to cut some jobs in an economically viable way.

Beam Delivery For A Laser Cutting Machine

For the majority of laser cutting applications the material is in a sheet format.

The advantage of the plotter mechanism when used as a laser cutter is that the beam can be delivered with a consistent power and minimal variation in focal point over a relatively large area.

When the CO2 laser power is <100w the types of material that are processed are usually non metals; materials such as acrylic, card, wood, textiles, etc. These materials are most efficiently processed at the 1000x600mm size, which provides for minimal material wastage, maximum efficiency of fume extraction and part loading/unloading.

Sectors that would benefit from using this type of machine are architects for model making, sign companies and point of sale fabricators to name but a few.

In recent years there has been a big increase in the number of educational facilities such as schools, Universities, etc who buy a laser cutter for schools to assist with Design & Technology subjects.

This type of machine is available in a range of laser powers typically from 25-100w. Higher powered lasers will deliver faster cutting speeds and often a superior edge quality but will also cost more to purchase as well as more to maintain/own over time.

This type of machine will typically be fitted with a plano-convex lens delivering a short focal length, such as 2.5” for example. The short focal length should be combined with a nosecone to deliver an air assist close to the material for increasing edge quality and minimising lens contamination.

An often overlooked part of the machine is the software. Most machines in this format are designed for laser engraving, which often is the least efficient way to use such a machine. Therefore, the software tends to be designed for the engraving process. This can be significantly limiting when using the laser as a cutting tool.

A good laser cutter will use software similar to that of a CNC router and have optimising features to minimise wasteful motion control movements as well as improving the output quality of the part that has been cut.

At Lotus Laser Systems we manufacture a wide range of plotters systems for laser cutting and our experts would be happy to advise you which configuration would suit your application best.

Most Common Types Of Laser Beam Delivery

Many people don’t realise that within a laser marking machine there are different ways to deliver the laser beam to the work piece and even fewer consider the massive difference that choosing the correct form of beam delivery can have on process times and output quality.

Contrary to popular conception it is not a good idea for a single format of system to be applied to all jobs even if technically it’s possible to do so.

Choosing the right form of beam delivery can determine whether or not you will meet customer price, quality and delivery requirements or even whether or not you will win the job at all and the wrong choice can have serious implications relating to system reliability, maintenance and running costs.

In a laser engraving machine there are most commonly two types of laser beam delivery:

1. Via a plotter type motion system that usually contains stepper or servomotors, linear bearing rails and belts. To this motion system are attached a series of 3 or 4 mirrors that deliver the beam via deflection to a focus carriage that usually contains a single layer plano-convex lens. The lens moves over the work area, which is usually large and rectangular in shape, to deliver the focused laser to the work piece; technically this is a flying optic laser.
These machines are commonly called a laser engraver or a laser cutter and predominantly incorporate a CO2 laser at the 10.6µm wavelength.

2. Via a sealed unit containing 2 mirrors that are attached to galvanometers; these are very accurate, high speed motors one of which turns through 0 degrees (X axis) and the other through 90 degrees (Y axis). The beam is focused through a fixed lens known as an F-Theta lens that at the 1µm wavelength is multi-layered and at 10.6µm is usually a single layer.
The work area is constraint by the characteristics of the lens and is usually quite small and circular in shape; technically this is known as a beam deflection laser.
 These machines are commonly called a galvo laser, a marking laser or sometimes a laser marker and can be fitted with a very wide range of laser wavelengths such as 355nm, 532nm, 1064nm (1µm) and 10.6µm.

At Lotus Laser Systems we manufacture at our UK facility all of the above mentioned system formats and our experts would be happy to advise you which configuration would suit your application best

Laser Engraving Machine Basics: CO2 vs Fiber

When selecting a laser engraving machine, the first step should be ensuring you choose the correct wavelength for the material you are working with. The wavelength will ultimately determine the results you get with various materials. The two most common wavelengths are 1 micron and 10.6 microns. At 10.6µm, CO2 laser tubes are used whilst at the 1µm wavelength; fiber is generally accepted as the best all round laser source.

1µm laser engraving machines are usually used on metals although there are a number of other materials that also mark very well such as polycarbonate. The small spot size a fiber laser engraving machine offers makes it the best choice when you are looking to mark or engrave metal with a high level of detail. The 10.6µm wavelength will not react with metal at low power although people often attempt to work around this by using chemical sprays which are generally time consuming, messy and highly toxic. Aside from the smaller spot size, one of the big advantages of the fiber laser source is that it is highly durable and is generally going to have a much longer life than the CO2 laser source which means you should get many more years of life from your machine. As expected, you are likely going to have a larger initial outlay when choosing the route of fiber technology.

10.6µm is the most common laser source and is often used to engrave wood or plastic and is what you are likely to see fitted to most standard flat bed laser cutter. Like fiber laser tubes, these can actually be delivered using both galvo and plotter systems although many people have not yet realised the major advantages of engraving with a galvo as opposed to a plotter. As mentioned, CO2 lasers are more geared towards dealing with woods and plastics so if you are working with these materials 10.6µm is certainly the way to go. One of the advantages of working with CO2 laser tubes is that their cost is generally significantly lower than their fiber counterpart. The trade off is that their expected life is shorter so you should be prepared to have to replace the tube more frequently.

Overall, there are a number of complex factors that will play a part in determining the right laser engraving machine for you. However, selecting the correct wavelength for your application should certainly be your number one priority.