Laser Processing:
Acrylic

Tips & Tricks for Acrylic Processing

CO2 lasers are the best possible tool for cutting and engraving acrylic. They offer the best conditions for producing illuminated signs, displays, decorative objects, toys and so much more. Here, you will be able to read all about how to select the correct materials and settings to achieve the best results.

Cast Acrylic vs Extruded Acrylic

Acrylic is produced by one of two methods: it's either cast (GS) or extruded (XT). Each method is unique and has its own set of distinguishing material properties. Ultimately, both kinds of acrylic can be processed very well. However, it is important to note that they behave quite differently to each other when laser processed. It's very useful to have a basic knowledge about these differences when deciding on a suitable acrylic for your chosen application.

Cast Acrylic (GS)

Cast acrylic is made by pouring a liquid mass between two glass plates. The result is a homogeneous, tension-free material with the same mechanical properties on the x and y axis. Due to this manufacturing process, the thickness tolerance is significantly higher - about 15% - which needs to be considered when completing applications with plug connections. The process is also more expensive than extruded which is why the product's price can be quite high. Laser cutting cast acrylic creates burr-free edges on both sides, and laser engraving yields beautifully white engravings which are otherwise impossible with extruded acrylic. Currently, Trotec only supplies an assortment of cast acrylic sheets.

Extruded Acrylic (XT)

Extruded acrylic is produced via an extrusion process. It presses an acrylic mass through a nozzle with your desired thickness, making it a quicker process than with cast acrylic. This manufacturing method gives the acrylic different mechanical properties in the x and y axis. It also has a lower thickness tolerance - 5% - and is very well suited for applications that involve plug connectors. When extruded acrylic is laser cut, you will be left with a beautiful flame polished edge that is much less sharp on one side. It's cheaper to produce, therefore cheaper to use for things like series productions and mass producing. It also requires much less power than cast acrylic. Laser engraving extruded acrylic is not recommended as the result will only ever be a matte grey.

Machine Setup for Acrylic Processing

Every single one of Trotec's CO2 laser machines are suitable for processing acrylic. For example, a Speedy 100 laser machine can cut and engrave acrylic to the same standards as the SP3000. The only real difference is the speed in which the machine works, as well as a slight variation in the quality of the results.

Laser Power Level

The laser power required for cutting acrylic depends greatly on the thickness of the sheet that needs to be cut, as well as your desired productivity. For a quick and trouble-free working method, we'd recommend a machine with 60 Watts of power or more.

Rule of Thumb: 10W laser power per 1mm sheet thicknesses = high cutting quality (20-25mm max thickness)

Choosing the Right Lens

Selecting the correct lens is a very important factor to consider when cutting acrylic. Remember: the thicker the material, the longer the focal length.

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

Adjusting the Focal Point

We suggest moving the focal point to the interior of the material whenever it is more than 6mm thick. This will help you achieve an even, homogeneous cut.

Remember: Move the focus to about ⅓ of the thickness of the material. For 6mm acrylic, z value = -2mm

Selecting the Nozzle & Setting Air Assist

When you're cutting acrylic, you should always use the nozzle with the largest diameter and - if possible - lessen your air-assist to a maximum of .2 bar. This will give your material enough time to completely cool off, meaning you will achieve glass-clear cutting edges every time. Ultimately, if a nozzle with a small diameter is used or if the air pressure is too high, the result will be a dull, milky or matte cutting edge due to the rapid cooling of the material.

Always Choose the Right Lens

We want to reiterate how important it is to select the correct lens at this point on your acrylic cutting application - the thicker the material, the longer the focal length should be!

Selecting the Correct Table

Akin to choosing the right lens, selecting the correct laser table is an equally important factor for achieving optimal results when processing acrylic. Depending on the size of your machine and application, there are many different tables you can choose from. We usually recommend the acrylic slat cutting table, or even the acrylic cutting grid table for most acrylic applications.

The acrylic slat cutting table will prevent 'kick-backs' while cutting, which is especially useful when cutting thick acrylic sheets (6mm or more), as well as for parts that are cut any larger than 100mm. Smaller parts might slide around or fall through the gaps of this table, so we don't recommend its use in these situations.

For those smaller parts (100mm or less) the acrylic cutting grid table, or the acrylic grid overlay on top of the vacuum are much more suitable. This is because the parts will always remain in a flat position, even after cutting. However, these configurations are only recommended for acrylic up to 8mm thick. For thicker acrylic, always use alternative cutting tables.

Cutting Table	Material Thickness	Size of Parts
Acrylic Slat Cutting Table	Acrylic sheets > 6mm thick	Parts cut wider than 100mm
Acrylic Grid Cutting Table	Acrylic sheets < 8mm thick	Parts cut smaller than 100mm

Using Exhaust Systems

Utilising an appropriate exhaust system is extremely important when cutting any kind of acrylic material. In fact, it is paramount when completing any kind of laser application. This is because the vapours within the machine can be dangerous to you, your machine and the environment. However, a good filtration system will suction these fumes out. Good ventilation is always 100% necessary to achieve a perfect cut, while a lack of ventilation could cause vapours to ignite and start a fire. Machines should never be left running unattended!

Always remember to treat your machine with care and respect - Trotec machines are the safest laser engravers and cutters on the market, but you still need to adhere to safety rules and ensure that safety features are running to their full potential.

More About Exhaust Systems

Acrylic Cutting Parameters

Acrylic usually requires a much higher cutting frequency than something like wood. The higher frequency ensures that the energy is transported evenly into the material, and your processes can be completed to a high standard. It usually causes a careful melting process to begin on the cutting edges, creating glass-clear, flame-polished edges.

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

If the frequency is too low, fine ridges or 'chatter marks' can become visible on the cutting edges. To counteract these, be sure to increase or lower the frequency accordingly. However, if the cutting speed is too low, you could be left with a cutting kerf underneath. This is a big fire-risk and we implore you to take extra care.

Remember: Determining your parameters is very important. You'll want them to be perfect to achieve a high-quality result, but also to remain safe.

Acrylic Engraving Parameters

When engraving acrylic, remember: less is more!

The best engraving results are always achieved when only the surface of the acrylic is scratched. You will be left with an elegant, white engraving result. If too much power is used, the engraving will be very deep, and it will lose its white appearance.

Tip - Engraving on the Reverse

Engraving acrylic from behind can give your result a very high-quality and smooth appearance. It will always be optimally protected against all external influences. Even when using printed acrylic, the product can look much better when printed on the reverse.

Remember: Don't forget to mirror the job! You'll be able to do this in your graphics program or the printer settings when you send it to the laser machine.

Graphics & Software Settings for Acrylic Processing

Minimal Nodes

The careful preparation of your graphics can significantly improve the processing quality when working with acrylic. Firstly, the number of nodes in the cutting contour needs to be reduced to a minimal amount, which allows the laser to process homogeneously without any necessary stops.

Start Cutting at the Optimal Point

Determining the perfect cutting start-point is also essential when processing acrylic. When the laser machine cuts into a material, it becomes visible from this point and cannot be avoided. Starting points that are situated 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 a discreet corner.

The thicker your acrylic, the better it is to define the start point outside your actual graphic. This is what we call a 'lead-in'. The lead-in should always be about 3-8mm outside of the finished contour and should make its way towards the actual contour in a straight, smooth line. You can easily draw this lead-in within your template, or you can use supplementary software packages like TroCAM as part of your work preparation.

Define the Cutting Sequence

The cutting sequence for individual objects can also have a heavy influence on the quality of larger quantities. If a lot of small objects are being cut, the material will heat up at the laser point. The risk of your material flaming up will increase here as well, not to mention the material may fuse back together once it’s been cut. If you want to cut lots of small graphics out of one large sheet, we suggest arranging the individual parts so that the material can cool off in between cuts. The cutting sequence is always visible in the graphics program (CorelDRAW, Adobe Illustrator, etc) within the level window, and it's automatically processed from the bottom up.

Trotec Acrylic: TroGlass

The Trotec acrylic product assortment contains a large selection is exciting acrylic sheets. It ranges from glass-clear to coloured sheets, all with different surface variations (shiny, satin, frosted, matte/gloss and combined). Sheets are available in many different thicknesses too, including 3, 4, 5, 6, 8, 10, 15 and 20mm. The sky is your only limit!

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