Milling acrylic: 6 useful tips

Do you need to cut a particular shape from an acrylic sheet? If so, it’s better to mill the perspex rather than to saw it. Milling is the preferred method, especially when complex shapes and professional edge finishing are required. Milling perspex using only standard DIY tools is a piece of cake with our 6 handy tips.

Requirements for milling acrylic sheet:

#1. Use cast acrylic sheet

In principle, it’s possible to mill both cast and extruded acrylic sheets. However, we strongly recommend that you opt for cast acrylic sheet when milling perspex. This is because the manufacturing process of extruded acrylic causes more internal stresses, making it more prone to breakages. Cast acrylic glass is much easier to machine and should always be the preferred choice for milling.

#2. Choose the right tool for milling PMMA

Professional plastic sheet converters have machines with a large bed to support the sheet material properly. In these CNC (Computer Numerical Control) devices, the acrylic sheet is clamped in a milling machine and processed with a computer-controlled, multi-axis milling cutter. But it’s easy to rout perspex using regular DIY tools, such as a wood milling machine or router.

The critical thing to remember is to make sure that your milling machine has a sharp blade and that it doesn’t get clogged up with chips. If your milling machine has a vacuum connection, we recommend using it. When you start milling, you create a lot of chips. That’s why it is also a wise precaution to wear safety glasses while milling.

#3. Adjust the cutter diameter to the thickness of the acrylic sheet

Use cutters with a cutting edge made of carbide (HSS) and choose the correct diameter cutter. How do you know which diameter cutter to use? Consult our handy guide below.

Tip: use a higher speed for smaller diameter cutters than for thicker blades. Find the right speed by first milling pieces of scrap material.

#4. Support the acrylic sheet and the cutter during milling.

Both the panel and the cutter must be well supported during milling. To prevent the acrylic sheet from vibrating during milling, place the acrylic on a solid surface. For this, use a wooden board in which the cutter can run. The top of the sheet also needs to be well supported. Make sure that the acrylic sheet is pressed firmly against the solid surface. Do this with the help of battens and screw clamps or vices that support the panel along the milling line. If you prefer to make straight milling lines, run the cutter along a straight bar.

#5. Mill your perspex in several stages

Depending on the sheet thickness, it may be necessary to mill your acrylic sheet in several stages. This does not apply to thin sheets with a thickness of 5 millimetres or less. You can usually mill these acrylic sheets in one pass. Make sure that you mill these thinner sheets against the direction of rotation of the cutter. This gives you a cleaner milled edge than with down milling.

Mill thicker sheets in several stages. Sheets up to 10 mm thick must be milled in two passes. Larger thicknesses take four steps. Even if you think that the sheet could be milled in three passes, our advice is to mill in four stages. At the fourth pass, run your mill slightly slower and use a lower throughput speed; this creates the most pleasing edge finish.

#6. Polish the milled edges of your acrylic sheet

For an even more beautiful and smoother edge finish, you can opt to polish the milled edges of your perspex sheet. Read how to do this in our blog Polishing acrylic.

What can you create when you mill acrylic?

Once you start milling, you can make any shapes you want from a sheet of perspex. Acrylic is usually milled to create circles, diagonal cuts, house numbers and other shapes. Frequently seen examples are the milled letters used for advertising and perspex signage.

Questions about milling acrylic

Do you have any questions about milling acrylic or are you not sure about which materials you need? Please don’t hesitate to get in touch; we’re happy to help.