Laser cutting and engraving acrylic

Tips and tricks for acrylic processing

CO2 lasers are an outstanding tool for processing acrylic. Laser cutting and laser engraving acrylic offers many application possibilities, including producing illuminated signs, displays, decorative objects, toys and more. Read on to discover how to select the ideal laser materials for your application and the laser settings which will give you the best results.

Cast acrylic vs extruded acrylic

There are two different types of acrylic, cast (GS) and extruded (XT). The different production methods used to create these materials leave the finished product with different material properties.
In principle, both types can be laser processed very well, however, the two types of materials behave differently during laser cutting and engraving. 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, resulting in a homogeneous, tension-free material with equal mechanic 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 laser acrylic is more expensive, resulting in higher costs than extruded acrylic.
Laser cutting cast acrylic creates burr-free cuts on both sides. Laser engraving also yields better results than with extruded acrylic, with a perfectly white engraved image being created.
At present Trotec's range of acrylic, TroGlass, 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 well suited to applications with plug connectors. When extruded acrylic is laser cut, it creates a flame polished cutting edge that is less sharp on one side. Extruded acrylic is generally less expensive, because of its production method and, as a series production is cheaper. 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 as unlike the white image produced on cast acrylic, extruded acrylic produces a matt grey result when laser engraved.

Machine setup for acrylic processing

Generally speaking, all CO2 laser machines from Trotec are suitable for acrylic processing. For example, a Speedy 100 can laser cut and engrave acrylic just as well as the SP3000, the differences only visible in terms of the processing speed and the quality of the finished results.

Laser power level

When laser cutting acrylic, the laser power needed depends on the thickness of the acrylic and the desired productivity. 60 watts or more is recommended.

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 laser cutting acrylic. 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 recommend moving the focal point to the interior of the material when it is more than 6 mm thick, as this allows you 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 laser cutting acrylic, the nozzle with the large diameter should be used and – if controllable – lessen the Air Assist to a max. of 0.2 bar. This will give the material enough time to cool off thus giving a glass-clear result on the edges.

In contrast, if a nozzle with the small diameter is used or the air pressure is too high, a dull, milky laser cutting edge is created as the material cools off too quickly.

Selecting the correct lens

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

The ideal table for acrylic processing

Selecting the right laser cutting table is equally important for achieving perfect acrylic processing results. Depending on the size of your application there are multiple table options. We recommend the acrylic slat cutting table or the acrylic cutting grid table, depending on your applications size.

An advantage of the acrylic slat cutting table is that it prevents kick-back during laser cutting, making it especially suitable for laser cutting thicker acrylic sheets (6 mm or more) and for parts that are cut larger than 100 mm. Smaller parts can tip and shouldn't be processed with this table.

For parts smaller than 100 mm, the acrylic cutting grid table or the acrylic grid overlay on the vacuum table are suitable as parts remain in a flat position after laser cutting. However, this work area is only recommended for acrylic up to 8 mm thick

Cutting table	Material thickness	Size of parts
Acrylic slat cutting table	Acrylic sheets > 6mm 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

A suitable exhaust system is indispensable when acrylic laser cutting, as with any laser application, so that the vapors in the machine room created during the laser cutting can be suctioned out. Sufficient ventilation is essential for achieving a high quality cut. Lack of ventilation can cause the vapors to ignite, leading to a fire. Laser machines should never be left unattended when operating.

Parameters for laser cutting acrylic

As a material, acrylic requires a higher frequency when laser cutting compared to other common materials such as wood. The higher frequency distributes the energy evenly into the material. This causes an even melting of the laser cut acrylic edges creating 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, also known as chatter marks, become visible on the laser cut edges. To counteract these, increase or lower the frequency of the laser cutting speed. However, if the cutting speed is too slow, this can lead to a cutting kerf below which increases the risk of fire.

It is important to figure out the perfect parameters when working with acrylic to work safely and efficiently.

Parameters for laser engraving acrylic

When laser engraving acrylic, the principle less is more should be applied.
The best results are achieved when only the surface of the acrylic is scratched, as this creates a white engraved image. Using a lot of laser power creates deep laser engraving results, however they will no longer be white.

Tip - Reverse laser engraving:

Engraving the acrylic on the back of the material gives the final result a higher quality and the engraving is better protected against external influences. Even with printing, the acrylic 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-laser-settings-acrylic-processing

Graphic and software settings for acrylic processing

Use a minimal number of nodes

Careful preparing your graphics can also significantly improve quality when laser cutting and engraving 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 laser cutting starting point

The definition of thelaser cutting start point is an essential factor. 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 of the material.

The thicker the laser acrylic used, the better it is to define the start point outside the actual graphic. This isknown as a 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. We also have a range of how to guides and tips & tricks available on our website and engraving supplies webshop.

Laser processing acrylic

Trotec acrylic assortment: TroGlass

With the TroGlass range of acrylics from Trotec, your creativity is your only limit. Featuring glass glass-clear acrylic in thickness of 3, 4, 5, 6, 8, 10, 15 and 20 mm and coloured acrylics in metallic, frosted, transparent, transluscent and fluorescent varieties, there is a TroGlass sheet for every application.

Discover the TroGlass laser acrylic range

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