Laser processing on acrylic

Tips and tricks for processing of acrylics

CO₂ lasers are ideal for laser cutting and engraving acrylics. They offer optimum conditions for fabricating illuminated signs, displays, decorative objects, toys and more. Here are some guidelines for choosing the correct materials and laser settings to achieve the flawless results.

Difference: cast and extruded acrylic

Acrylic is manufactured in two different ways, it can be cast (GS) or extruded (XT). Each method creates its own set of material properties.
In principle, both versions can be processed successfully, however, they react differently while being processed with a laser. It is helpful to have a basic understanding about the options when choosing a suitable acrylic material for your application.

Cast acrylic (GS)

Cast acrylic is poured as a liquid mass between two glass plates. The result is a homogeneous, tension-free material with equal mechanical properties in directions x and y. Due to this manufacturing process, however, the thickness tolerance is significantly higher and is approx. ±15%, which must be observed for applications with plug connections. The manufacturing process for cast acrylic is more expensive which is why it costs more than extruded acrylic.
Laser cutting cast acrylic creates burr-free cuts on both sides. Laser engraving also yields better results than with extruded acrylic - a perfectly white engraved image results.
Currently, the Trotec material assortment only contains cast acrylic sheets.

Extruded acrylic (XT)

Extruded acrylic is produced through an extrusion process that presses an acrylic mass through a nozzle with the desired thickness. This manufacturing method gives the extruded acrylic contrasting mechanical properties in the x and y directions. In addition, it has a lower thickness tolerance of ±5% and because of is very well suited to applications with plug connectors. When extruded acrylic is cut with a laser, it creates a flame polished cutting edge that is less blunter on one facet. Extruded acrylic is more cost effective to manufacture, and is thus cheaper as a series production. As a rule, extruded acrylic requires less laser power than for cast acrylic in the same sheet thickness. Laser engraving on extruded acrylic is not recommended because the result is only a matte gray.

Machine setup for acrylic processing

In principle, all CO2 laser machines from Trotec are suitable for processing acrylic. For example, a Speedy100 can cut and engrave acrylic just as well as the SP3000. The variences are only noticable in terms of the speed of processing and the quality of the finished product.

Laser power level

The laser power required for cutting acrylic depends on the thickness of the acrylic sheet and the needed productivity. For the most productive work procedure, we suggest a laser power of 60 watts or more.

The rule of thumb is: 10 watt laser power per 1 mm sheet thickness for a high quality cut
(Maximum thickness of 20-25 mm)

Selecting the correct lens

Choosing the correct lens plays an extremely important part when cutting acrylics. The thicker the material, the longer the focal length of the lens should be.

Material thickness	Speedy Series	SP Series
thin acrylic sheets < 5mm	2" lens	2,5" lens
thick acrylic sheets > 5 mm	2,5" lens	5" lens

Move the focal point to the material interior

We suggest adjusting the focal point to the interior of the material when it is more than 6 mm thick to achieve an even, homogeneous cut.

The following guiding values apply: Move focus to about 1/3 of the thickness of the material.
For 6 mm acrylic, it would be a z value of -2 mm.

Selecting the nozzle and setting the Air Assist

When cutting acrylic, you should always use the nozzle with the large diameter and – if controllable – lessen the Air Assist to a max. of 0.2 bar. This gives the material enough time to cool down - and results in glass-clear edges. On the other hand, if a nozzle with the small diameter is used, or the air pressure is too high, the result is a dull, milky cutting edge because the materials cooled off too rapidly.

Selecting the correct lens

Choosing the correct lens plays an extremely important part when cutting acrylic. The thicker the material, the longer the focal length of the lens should be.

Selecting the correct table

Choosing the correct cutting table is an just as important for achieving perfect results with acrylics. There are multiple options, depending on the size of your application. We recommend the acrylic slat cutting table or the acrylic cutting grid table depending on the size of the application.

The acrylic slat cutting table prevents kick-back during cutting and because of this, is especially suitable for cutting thicker acrylic sheets (6 mm or more), as well as for parts that are cut larger than 100 mm. Smaller parts could tip and are therefore not ideally suited for this table design.

For parts smaller than 100 mm, the acrylic cutting grid table or the acrylic grid overlay on the vacuum table are well suited, because the parts remain flat after cutting. However, this work surface is only recommended for acrylics up to 8 mm thick. For thicker acrylic, you should always use the other version.

Cutting table	Material thickness	Size of parts
Acrylic slat cutting table	Acrylic sheets > 6 mm thick	Parts that are cut wider than 100 mm
Acrylic grid cutting table	Acrylic sheets < 8 mm thick	Parts that are cut smaller than 100 mm

Using an exhaust system

Using the appropriate exhaust system is crucial with acrylic cutting, as with any laser application, so that the vapors in the machine room created during cutting can be suctioned out. Adequate ventilation is paramount to achieve a high quality cut. A lack of ventilation can result in the vapors igniting and creating a fire. Laser machines should never be left operating unattended.

Parameters for laser cutting acrylic

Acrylic materials, need a higher frequency when laser cutting, compared to wood for example. The raised frequency evenly distributes the energy onto the material. This results in an even melting of the cutting edges which produces a glass-clear, flame-polished edge.

For GS materials, we recommend a frequency of 5,000-20,000 Hz
For cutting XT materials, a frequency of a max. of 5,000 Hz.

If the frequency is too low, fine ridges, called "chatter marks", become visible on the cutting edges. To eliminate these, raise or reduce the frequency of the cutting speed. However, if the cutting speed is too slow, this can lead to a cutting kerf below - which increases the risk of fire.
Determining the ideal parameters is very important, in other words, when working with acrylic, work safely and efficiently.

Parameters for laser engraving acrylic

When engraving acrylic, the following rule of thumb applies: less is more.
The most desirable results are achieved when only the surface of the acrylic is scratched, creating a white engraved image. If too much power is used, the engraving results may appear deep, however, they will no longer be white.

Tip - Engraving on the reverse side:

Engraving the acrylic on the reverse side gives the finished products a higher quality and the engraving is better protected against external elements. Even with printed acrylic, the product appearance is better when printed on the back.

Caution: Don’t forget to mirror the job!
This can be done either in the graphics program or simply directly in the printer setting when you send the job to the laser.

Graphic and software settings for acrylic processing

Minimum number of nodes

The careful preparation of the images can also significantly improve quality when working with acrylic. First, the number of nodes in the cutting contour needs to be reduced to a minimum. This allows the laser to process homogeneously without unnecessary stops.

Optimal selection of the cutting start point

The definition of the cutting start point is also extremely important. When the laser cuts into the material, it is visible at this point and cannot be avoided. Start points that are on a straight line or in the middle of a curve are especially noticeable. That’s why a start point should always be placed in an unnoticeable corner.

The thicker the acrylic being used, the better it is to define the start point outside the actual graphic. This is a so-called lead-in. The lead-in should be about 3-8 mm outside the finished contour and go to the actual contour in a straight line. You can draw this lead-in easily with your graphic program, or use our supplementary software package TroCAM as part of the work preparation.

Defining the cutting sequence

The cutting sequence for individual objects can also have an influence on the quality for larger quantities. If many small objects are being cut in the area, the material heats up relatively strongly at this spot, and the risk of fire increases. If you want to cut many small graphics from one large sheet, we recommend that you arrange the individual parts so that the material can cool off in between cuts. The cutting sequence is visible in the graphic program (CorelDraw, Adobe Illustrator) in the level window and is always processed from down to up.

Do you have more questions about working with acrylic?

Our laser experts will be happy to help you.

Trotec acrylic assortment: TroGlass

The Trotec acrylic product assortment contains a large selection. It ranges from glass-clear acrylic in thickness of 3, 4, 5, 6, 8, 10, 15 and 20 mm to colored acrylic sheets with different surface versions (shiny, satin, frosted, matt/shiny combined...) Your creativity won’t have any limits.

Everything about TroGlass in the Trotec Webshop