Laser cutting and engraving on acrylic can be used to create marketable products such as signs, displays, letters or jewelry.
By using the right laser cutter and following the right technique, you can produce acrylic products with smooth edges and a polished finish.
This article is about the process of laser cutting acrylic and everything you need to know to do it successfully.
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Laser Cut Acrylic
Laser cutting machines not only provide fast cutting speed, but also provide high precision and good surface finish.
CO2 lasers are best for cutting acrylic as it works well even on clear acrylic. Typically, 10W of laser power is required to cut 1mm thick acrylic, so it is recommended to use a high-energy CO2 laser rated at 60W or higher to process acrylic.
The reason a CO2 laser can even cut clear acrylic is because of its wavelength (9 to 11 µm), acrylic easily absorbs and evaporates.
Whereas the diode laser will pass through the clear acrylic without any significant effect on the acrylic workpiece.
Acrylic is a type of plastic, so you can use techniques similar to laser cutting or engraving plastic.
Types of acrylic suitable for laser cutting
According to the manufacturing process, there are two main types of acrylic: extruded acrylic and cast acrylic.
It is important to understand both because they behave differently than laser processing.
A good understanding of the difference between the two will help you choose the right one for your application.
Extruded acrylic is manufactured by extruding an acrylic substance through an opening of the desired thickness.
The extrusion process results in non-uniform mechanical properties of the material along the x and y directions.
It is relatively cheaper than cast acrylic and has good optical properties.
Extruded acrylic is highly impact resistant, three times more durable than window glass of the same thickness, and 50% lighter than glass.
Laser cutting extruded acrylic will produce clean cuts and flame polished edges.
And laser engraving extruded acrylic will cause the engraving to be gray, so it is not suitable for engraving.
In general, extruded acrylic is easier to cut than cast acrylic of the same thickness and requires relatively less laser power.
Cast acrylic is a high-quality acrylic made by casting the monomer methyl methacrylate between two pieces of glass.
The glass and methyl methacrylate components then polymerize to form a piece of cast acrylic.
This manufacturing process produces a homogeneous material with uniform mechanical properties in all directions.
Cast acrylic is more expensive than extruded acrylic, but offers better optical properties.
Laser cut cast acrylic will produce a nice surface finish with some streak marks around the edges.
Highly recommended for laser engraving due to its excellent frost white engraving output.
Both cast and extruded acrylics are available in a variety of different shades and colors.
Laser cutter setup for acrylic cutting
The power of the laser module determines the ability of the laser cutting machine to cut acrylic.
The higher the power, the higher the ability to cut thick materials.
However, low-power diode lasers can also be used to engrave acrylic, and can even cut satisfactorily with multiple passes.
However, it is recommended to use a CO2 laser rated at approximately 60W to cut 0.23" (6mm) thick acrylic sheets.
The cutting speed determines the surface finish of the cut performed by laser cutting.
Laser cutting acrylic at low speed will produce a glass-clear flame-polished edge without any burrs, but if you notice chatter marks on the cut edge, then you should consider increasing the cutting speed.
Generally speaking, when using a 60W CO2 laser to cut 0.2 inch (5mm) thick acrylic sheet, it is recommended to set the laser power to 80% and the cutting speed to be low, about 0.5 inch/sec (5mm/sec).
Likewise, for high quality grating engraving, the recommended laser power is 13% at a speed of approximately 9.8 in/sec (250 mm/sec).
You can also refer to the laser cutting thickness and speed charts to determine the ideal laser parameters for your application.
Atomstack air assist is usually not required when cutting acrylic sheet, but is useful for thicker sheets.
Air assist for cutting acrylic should be low pressure (approx. 0.2 bar) air assist with a large size laser nozzle.
The low air pressure and large size of the laser nozzle give the acrylic enough time to cool while creating a glass-clear edge.
When laser cutting acrylic, the laser beam can cut through the acrylic and be reflected back by the metal table.
This reflected laser beam can strike the workpiece from below and cause tiny defects called "reflection marks".
To solve this problem, you can use the needle table to lift the acrylic workpiece from the table and prevent the reflected laser from causing any defects in the workpiece.
When using this technique, make sure to cut the inner geometry first, as unsupported parts will fall onto the table after cutting.
The focal length of the laser determines the optimal distance between the workpiece and the laser head.
Focused laser for fast cutting and good surface finish.
Defocused focus is recommended when laser cutting acrylic thicker than 0.25".
In this case, the new focal point should be set approximately 1/3 of the material thickness inside the workpiece surface.
This will improve the edge quality of the cut and produce a smooth finish.
You can also perform subsurface laser engraving by setting the focal point of the laser inside the acrylic block.
Subsurface laser engraving is a technique used to engrave inside a material without affecting the outer surface.
While it works best with glass, you can also get good results with clear acrylic.
While laser-cut acrylic generally does not produce toxic fumes, it may adversely affect your health in the long run.
Therefore, it is recommended to use the laser cutter in a well-ventilated area with a dedicated exhaust system.