Tips and tricks for acrylic processing

CO2?lasers ?are outstanding for?laser cutting and laser engraving acrylic . They offer optimal conditions for producing?illuminated signs ,?displays ,?decorative objects ,?toys ?and more. Here are some guidelines for selecting the right materials and laser settings to achieve the best results.

Difference: cast and extruded acrylic

Acrylic is produced through two different methods, it can be?cast (GS)?and?extruded (XT).?Each method produces its own set of material properties.In principle, both versions can be processed very well, however, they behave differently during the laser processing. It is useful to have basic knowledge about the differences when deciding on 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 different mechanical properties in the x and y directions. In addition, it has a?lower thickness tolerance of ±5%?and is thus 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 sharp on one side. Extruded acrylic is cheaper to produce, 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 working with acrylic. For instance, a?Speedy100 ?can cut and engrave acrylic just as well as the?SP3000 . The differences are only visible in terms of the speed of processing and the quality of the results.

Laser power level

The laser power needed for cutting acrylic depends on the thickness of the acrylic sheet and the desired productivity. For a productive work method, we recommend 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 cutting quality (up to a thickness of 20-25 mm)

Selecting the correct lens

Selecting the correct lens plays an essential role when cutting acrylic. The thicker the material, the longer the focal length of the lens should be.?

Move the focal point to the material interior

We recommend moving 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 definitely use the?nozzle with the large diameter? and – if controllable –?lessen the Air Assist to a max. of 0.2 bar. That gives the material enough time to cool off - and glass-clear edges result. In contrast, 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 material cools off too quickly.

Selecting the correct table

Selecting the right cutting table is an equally important criterion for achieving perfect results in acrylic. There are several versions, 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 is thus especially suitable for cutting thicker acrylic sheets (6 mm or more) and for parts that are cut larger than 100 mm. Smaller parts can tip and are thus not suitable 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 suitable since the parts remain in a flat position after cutting. However, this work area is only recommended for acrylic up to 8 mm thick. For thicker acrylic, you should always use the other version.

Using an exhaust system

Using an appropriate?exhaust system ?is indispensable with acrylic cutting, as with any laser application, so that the vapors in the machine room created during cutting can be suctioned out. Sufficient ventilation is absolutely necessary to achieve a high quality cut. A lack of ventilation can cause the vapors to ignite and lead to a fire. Laser machines should never be left operating unattended.

Parameters for laser cutting acrylic

Acrylic, as a material, requires a?higher frequency ?when laser cutting it compared to wood, for example. The higher frequency brings the energy evenly into the material. This causes an even melting of the cutting edges which creates 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, so-called chatter marks, become visible on the cutting edges. To counteract these, increase or lower 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. Figuring out the perfect parameters is very important, in other words, when working with acrylic to work safely and efficiently.

Parameters for laser engraving acrylic

When engraving acrylic, the principle applies: less is more. The best 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 be deep, however, they will no longer be white.

Tip - Engraving on the reverse side:

Engraving the acrylic on the back gives the final result a higher quality and the engraving is better protected against external influences. Even with printed acrylic, the product looks better when printed on the back.

Caution: Don’t forget to mirror the job! You can do this 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 graphics 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 essential. 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.

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.

Do you have more questions about working with acrylic?

Our laser experts will be happy to help you. Contact us!