Laser Cutting and Engraving Acrylic-Expert Guide

Laser Cutting and Engraving Acrylic-Expert Guide

Laser Cutting and Engraving Acrylic-Expert Guide

Acrylic or plexiglass is an affordable, versatile material with glass-like transparency and plastic-like durability.

Laser cutting and engraving on acrylic can be used to create sellable products like signs, displays, letters, or jewelry.

By using the right laser cutting machine and following the correct technique you can create smooth-edged, and polished acrylic products.

This article is all about the process of laser cutting acrylic and everything you need to know to do this successfully.

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Laser Cutting Acrylic

A laser cutter not only provides fast cutting speed but also provides high precision with a good surface finish.

A CO2 laser is best suitable for cutting acrylic because it works well even on transparent acrylics. Generally, 10W of laser power is required to cut through 1mm thick acrylic, therefore a high-energy CO2 laser with a power rating of 60W or higher is recommended for working with acrylics.

The reason that a CO2 laser can even cut through clear acrylics is its wavelength (9 to 11 µm), which acrylics absorb easily and vaporize.

Whereas a diode laser will pass through a clear acrylic without having any significant effect on the acrylic workpiece.

Acrylic is a type of plastic and hence you can follow similar techniques you would use for laser cutting or engraving plastics.

Types of Acrylic Suitable for Laser Cutting

Based on their manufacturing process, there are two main types of acrylics: Extruded acrylics and Cast acrylics.

It is important to understand both because they behave differently to laser processing.

Having good knowledge of the difference between the two will help you choose the right one for your application.

Cast Acrylic vs Extruded Acrylic
Cast Acrylic vs Extruded Acrylic (Source: Trotec)

Extruded Acrylic

Extruded acrylic is manufactured by extruding an acrylic mass through an opening of desired thickness.

The extrusion process results in non-uniform mechanical properties in the material along the x and y directions.

It is comparatively cheaper than cast acrylic and has good optical properties.

Extruded acrylics have high impact resistance and can be three times more durable than a window glass of the same thickness while weighing being 50% lighter than glass.

Laser-cutting extruded acrylics will result in a clean cut with flame polished edges.

Whereas laser engraving extruded acrylics will result in a grayish hue to the engraving and therefore is not ideal for engraving. 

In general, extruded acrylic is easier to cut and requires comparatively less laser power than cast acrylic of the same thickness.

Cast Acrylic

Cast acrylic is a high-quality acrylic made by casting a monomer, methyl methacrylate, between two sheets of glass.

The glass and methyl methacrylate assembly then undergoes polymerization and a sheet of cast acrylic is formed. 

This manufacturing process results in a homogenous material with uniform mechanical properties in all directions.

Cast acrylic is comparatively more costly than extruded acrylic but offers better optical properties.

Laser cutting cast acrylic will result in a good surface finish with some striation marks along the edge.

It is highly recommended for laser engraving because of its excellent frosty-white engraving outputs.

Both, cast and extruded acrylics, are available in a variety of different shades and colors.

Laser Cutter Setup for Acrylic Cutting

Laser Power

The power of the laser module determines the ability of the laser cutter to cut through the acrylic.

Higher the power, higher is the ability to cut through thick material.

However, a low-power diode laser can also be used to engrave acrylic and can even perform satisfactory cuts with multiple passes.

But a CO2 laser with a power rating of around 60W is recommended to cut through acrylic sheets as thick as 0.23 inches (6mm).

Cutting Speed

The cutting speed determines the surface finish of the cuts performed by laser cutting.

Laser cutting acrylics at low speed produces a glass-clear, flame polished edge without any burrs, but if you find chatter marks along the edge of the cut, then you should consider increasing the cutting speed.

Generally, when using a 60W CO2 laser for cutting a 0.2 inches (5mm) thick acrylic sheet, it is recommended to set laser power at 80% with a low cutting speed of around 0.5 inches/sec (5mm/sec).

Similarly, for high-quality raster engraving, the recommended laser power is 13% with a speed of around 9.8 inches/sec (250mm/sec).

Air Assist

Air assist is not usually required when cutting thin sheets of acrylic but is useful for thick sheets.

The air assist used for cutting acrylic should be a low-pressure (around 0.2 bar) air assist with a large-size laser nozzle.

This low air pressure and large-size laser nozzle allow enough time for the acrylic to cool down while forming glass-clear edges.

Cutting Table

When laser cutting acrylic, the laser beam can slice through the acrylic and get reflected back by the metallic work table.

This reflected laser beam can strike the workpiece from underneath and cause tiny defects called ‘reflection marks’.

In order to resolve this problem, you can use a pin table to elevate the acrylic workpiece from the work table and prevent the reflected laser to cause any defect in the workpiece.

While using this technique, make sure to cut the inner geometry first as the unsupported part will drop onto the work table after it is cut.

Laser Cutting on Pin table
Laser Cutting on Pin table (Source: Epilog Laser)

Laser Focus

The focal length of a laser determines the optimum distance of the workpiece from the laser head.

A focused laser results in quick cutting speed with a good surface finish.

While laser-cutting acrylic with a thickness of over 0.25 inches, it is recommended to defocus the focal point.

In such cases, the new focal point should be set inside the surface of the workpiece at around 1/3rd of the thickness of the material.

This will improve the edge quality of the cut and produce a smooth finish.

You can also perform sub-surface laser engraving by setting the focus point of the laser inside the block of acrylic.

Sub-surface laser engraving is a technique used to make engravings inside the material without affecting the outer surface.

Although it works best for glass, you can also get good results with clear acrylics.

Exhaust System

Although laser cutting acrylic generally does not produce toxic fumes, it might have an adverse effect on 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.

Steps For Laser Cutting Acrylic

With a good laser cutter at hand and knowledge about laser cutting acrylics, you can make many acrylic projects that sell well.

You must also be aware of the laser safety risks, hazards, and control measures before you start operating any laser equipment.

Here are the steps involved in laser processing acrylics:

Creating the design

A good vector design is a primary requirement for all the laser cutting processes and it actively affects the quality of the final product.

Preparing the design in LightBurn
Peparing a vector design for cut

You can follow these tips to ensure a good quality vector design for laser cutting and engraving.

Starting Point

Always choose the starting point of the cut in such a way that it is the least visible corner of the final product.

The starting point of the laser cutting usually has a rough surface finish with a slight over-burn.

For thick acrylic material, it is recommended to have the starting point outside the actual geometry of the cut , this is known as 'lead-in'.

Around 0.1 - 0.3 inches (3-8 mm) of lead-in is recommended and it should connect with the actual geometry in a straight line.

Minimum Anchor Points

A good vector drawing should have minimum anchor points in order to avoid the unnecessary stopping of the laser.

A continuous contour ensures a homogenous cutting process with an excellent surface finish.

Cutting Arrangement

While cutting multiple components from a single sheet of acrylic, it is advised to arrange the cutting sequence properly.

There should be enough cooling time in between the successive cuts performed in one segmented area to avoid overheating.

Performing Test Runs

Test runs are necessary when working with new material or new designs.

It enables you to understand various machining parameters and improve the quality of the final product.

While laser cutting acrylics, you can improve the quality of the edge by changing the cutting speed, frequency, and focal point of the laser after every test run.

Test runs can also help you to understand the work area and position the workpiece in such a way that there is minimum wastage of the material.

The Final Cut

With the proper adjustments after the test runs, you can begin the final cut and get a glass-clear cut with flame polished edge.

While engraving acrylic, you can engrave on the back of the acrylic sheet to attain a clear surface on the front which will also protect the engraved surface from any external factors.

To do that, remember to mirror the vector image of the job in the CAD/CAM software before you start engraving.

Laser cut Acrylic
Laser-cut Acrylic (Source: Etsy)

Advantages of Laser Cutting Acrylic

Laser cutting acrylic offers many advantages over traditional cutting techniques.

Acrylic LED gifts (Source: Etsy)
Acrylic LED gifts (Source: Etsy)

Quality

Laser cutting acrylic results in clean cuts with flame polished edges that do not require any post-processing.

This reduces the machining time and results in higher throughput. 

High Speed

Laser cutting acrylic enables a high production rate because of its high cutting speed.

It also provides the ability to cut acrylic in almost any geometry with flexible contour designs and eliminates the need for any secondary machining.

Precision

The high accuracy and repeatability of laser cutters ensure high precision and good quality cuts even when mass producing an item.

This precision is also useful while engraving acrylic with complex designs.

Versatility

The laser cutter provides the privilege of cutting, engraving, or marking the acrylic on the same machine, just by regulating the power and cutting speed of the laser cutter.

Challenges in Laser Cutting Acrylic

Despite offering so many advantages, laser cutting also has some drawbacks and limitations.

High Initial Cost

The price of Laser cutters can be fairly high when compared to traditional cutting equipment.

However, the high efficiency and low average operational cost of laser cutters make up for this disadvantage, but the initial cost is still quite high.

Thickness Limitation

Although laser cutters have a quick cutting speed, this speed decreases with the increase in thickness of the workpiece.

Depending on the power of the laser cutter, you might even have to perform multiple passes to cut through a thick acrylic sheet.

Need for Expertise

There is a reasonable learning curve before you can create great-looking products with laser on acrylic.

Toxic Fumes

The fumes produced while laser cutting acrylic might not be lethally toxic but a proper ventilation system is necessary.

These fumes can cause irritation to the lungs which can be a serious issue when inhaling it on a daily basis.

Best Laser Cutters for Acrylic

Depending upon the laser power, performance, and material capability, here are some of the best laser cutters that give good results with acrylic.

OMTech AF2028-60

OMTech-60 is a powerful laser cutter that offers a work area of 20" x 28" and the two-way pass-through door provides the opportunity to work with even larger workpieces.

It comes with a high-power 60W CO2 laser that enables OMTech to cut through 1/4" thick acrylic sheets.

The electric-lift workbed and auto-focus laser head make it a handy machine to work on acrylics of various thicknesses.

Depending upon the type and thickness of acrylic, it offers a maximum engraving speed of 23.6 inches/second (600 mm/s).

Glowforge Pro

Glowforge Pro is an easy-to-use laser cutter with a sleek design that offers a work area of around 19.5” x 11” with a two-way slit that provides the opportunity to work with even larger workpieces.

It has a 45W CO2 laser that can perform through cuts on thick acrylics sheets up to 1/7".

The low-powered laser module is complemented by its ability to make highly precise cuts with an accuracy of around 0.001 inches.

It offers features like a simple interface, auto-focus, and built-in cameras that help in the easy adjustment of the cutting layout.

Another important feature of the Glowforge Pro is its inbuilt air-assist that can be very useful while laser-cutting acrylic.

Full Spectrum Laser Muse Core

Muse Core from Full Spectrum Laser offers a work area of around 20” x 12” and can work with up to 2.5" thick workpieces.

It is a desktop laser engraver/cutter that offers a 40W CO2 laser and an add-on option to upgrade it to a 45W laser module.

The 40W laser of Muse Core can cut up to 1/7" thick acrylic and can perform high-resolution engravings of 1,000 dpi.

Full Spectrum provides various add-on accessories like air compressor, exhaust fan, and additional lenses that can improve its overall laser cutting performance.

Final Thoughts

With good design skills and knowledge of cutting acrylic/plexiglass, you can start making profitable projects that you can sell.

Choosing the right acrylic for the job and having a good vector design are equally significant parameters for high-quality output.

Irrespective of the type of acrylic chosen, make sure to use a pair of laser safety glasses that are appropriate for your laser machine.

Although laser cutting has some disadvantages, the advantages far outweigh those and make it a great way to make acrylic products.

Laser Cutting and Engraving other Materials

Check out these guides on laser cutting some popular materials.

MaterialLink to Guide
PaperLaser Cutting Paper
AluminumLaser Cutting and Engraving Aluminum
LeatherLaser Cutting and Engraving Leather
PlasticLaser Cutting and Engraving Plastic
PolypropyleneLaser cutting polypropylene
BrassLaser Engraving Brass
FabricLaser Cutting Fabric
FoamLaser Cutting Foam
PlywoodLaser Cutting Plywood
GlassLaser Cutting Glass
VinylLaser Cutting Vinyl

Laser Cutting Guides for other Materials

Frequently Asked Questions (FAQ)

What is a pin table?

A pin table is a DIY work table for laser cutting, which supports the workpiece by rows of pins. These rows of pins elevate the workpiece from the metallic base table, thereby reducing the effect of the reflected laser beam on the workpiece.

What is a vector design?

Vector design or vector graphic is the image made by geometrical lines and shapes that are based on mathematical equations. These drawings generally consist of the outline of the design to be cut or engraved and can be scaled without having any effect on the quality of the drawing.

What are anchor points?

Anchor points in a vector image are basically the guide points of a segment that can be used to control the direction and curvature of the path. For example, a line has only two anchor points (the start and the endpoint), but a circle has at least four anchor points to control its size and curvature.

About John

Hey I'm John. I talk about CNCs and Power Tools at Mellowpine. I'm a CNC hobbyist who has been making CNCs and writing about CNCs for a while. I currently also work as a consultant for business owners and hobbyists setting up their own CNCs. If you have any questions related to CNC, I'd be happy to answer them. Reach me at john@mellowpine.com

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John

Hey I'm John. I talk about CNCs and Power Tools at Mellowpine. I'm a CNC hobbyist who has been making CNCs and writing about CNCs for a while. I currently also work as a consultant for business owners and hobbyists setting up their own CNCs. If you have any questions related to CNC, I'd be happy to answer them. Reach me at john@mellowpine.com

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