Both cast and extruded acrylic sheets can be milled, although you must take the internal stresses into account when milling extruded acrylic. If you know that the acrylic will have to be milled before purchasing the sheet material, we recommend that you always opt for cast acrylic. Milling is preferable to sawing acrylic sheets, especially with complex shapes and when edge finishing is important. In this article, we provide you with the most important advice for milling acrylic.
Requirements for milling acrylic sheet:
The right tool for milling acrylic
Professional processors of acrylic sheets have machines with a large bed on which the sheet material is well supported. This stability is very important to prevent cracks. Acrylic can also be milled very well with regular DIY tools, such as a wood milling machine/router. The most important thing is that your milling machine has a sharp milling cutter and that the chip removal is free. Does your milling machine have a connection for a vacuum cleaner? Then you should definitely use this.
Use milling cutters with one carbide cutting edge (HSS) and choose the correct milling diameter. For milling sheets with a thickness of up to 5 millimetres, use a milling cutter with a diameter of 4 millimetres, for sheets up to 10 millimetres use a milling cutter of up to 6 millimetres. For larger thicknesses, we recommend a cutter of 8 – 10 millimetres. For smaller cutters, use a higher speed than for thicker cutters, we recommend that you find the correct speed by milling pieces of scrap material.
Preparations for milling acrylic
It is extremely important that the acrylic sheet and the cutter are properly supported during milling. The sheet must not vibrate during processing so place the sheet on a solid surface, preferably one into which the cutter can run, such as a wood board. The top of the sheet must also be well supported and it must be pressed well against the surface. For this, use slats and clamps or glue clamps that support the sheet along the milling line. Do you want to make straight milling lines? Then run the cutter along a straight bar.
Milling different sheet thicknesses
Depending on the sheet thickness, it is necessary to mill the sheet in different ways. Thin sheets, up to a thickness of 5 millimetres, can usually be milled in one pass. We do recommend that you mill these thinner sheets against the direction of rotation of the cutter, which will produce a cleaner edge than when milling along with it. Do you want to mill extruded acrylic? Then we advise you to mill along with it.
Thicker sheets must be milled in several passes, sheets up to 10 millimetres can be milled in two passes, larger thicknesses can be done in four passes. Even when the sheet can be milled in three passes, we recommend milling in four passes. With the fourth pass, let the cutter run a little slower and use a lower transfer speed, which gives you a better edge finish.