twigtheoracle

guides

Cutting and Engraving Acrylic on a 60 Watt Epilog Helix Laser Cutter

A bunch of notes that I use to cut and engrave 1/8" acrylic on a 60 watt Epilog Helix laser cutter (exact settings are at the bottom). As a couple of initial notes, the acrylic I use is ChemCast Cast Acrylic, which comes in virtually every single color and with transparent/opaque versions. Mask refers to the covering that protects acrylic from chipping when it is cut with sharp tools (like a table saw). Also, all laser cutters are different so even if you are using the exact same laser cutter, play around a little before cutting/engraving for real.


Cutting With and Without Masks

The purpose of cutting acrylic with masks is to have all burn marks be on the mask, which can then promptly be removed. On the bottom, you get scorch marks, from when the laser penetrates too far and vaporizes the vector grid underneath the acrylic. If cutting with a mask, the bottom mask is the one you always want.

image of no top mask effect goes here

perhaps show a bunch of different size holes?

The top mask is only required when cutting small things (smaller than a 1/4" hole). If the top mask is not left on, you get marks around the cut like shown in the picture to the left. However, these marks are not the end of the world, they can only be seen under certain light angles, however, they do detract from the aesthetics.

The downside to cutting with masks comes apparent when cutting many small parts. It is difficult and very time consuming to remove the masks from say 150 tiny circles without fingernails of literal steel (I speak from experience). Thus, when cutting many small parts, it is advisable to cut without a mask.

The downside to cutting without masks is somewhat shown in the image above. On the bottom, there will be some scorch marks, and on the top you get heat marks. Scorch marks can be very eaisly cleaned off with isopropylkl alcohol, however, the heat marks will presist unless you sand them off, which many leave scratch marks unless you are careful.

To sum, the decision of cutting with and without a mask on is a question of which will result in more post processing. If you are making a few large parts, cut with the mask on and remove it after cutting. If you are making many small parts, cut without the mask and get your alcohol ready.


Engraving/Etching

Engraving, also know as etching or rastering, can be thought of as making tons of micro-scratches in a constrained area to produce a shade different from the base acrylic. When engraving, make sure that you are using cast acrylic (instead of extruded) for a better end result. Also, note that the advice below only applies to my specific application, which is text only. Engraving images is a whole new beast that requires a lot of trial and error that I have not done.

engraving speed limits go here

Engraving is different from cutting in that the settings are not cut and dried. When engraving, there is a "speed limit" based on the smallest left right movement the laser head has to make (the settings are shown on the left).

Speed limits exist because engraving involves very fast left right movement. If you don't slow down on smaller engraves, then the acceleration from whipping back and forth will wear down the driving stepper motor. It's not a super big deal to go faster than the speed limit, but over time it will increase maintainance and therefore the cost of the machine.

Engraving or Etching can also be done with a mask or without a mask. Engraving without a mask requires lower power and no post processing. Engraving with a mask requires a lot more power and a tiny bit of post processing (as well as lower quality). It may seem like engraving without a mask is the better way to go, but that increases your post processing if you cut afterwards.

The post processing involved with engraving with a mask is due to two primary reasons. One, when peeling the mask off of engraved text, letters with holes like "o" and "p" will leave mask behind in the hole. Then you have to peel off mask that got left behind. Two, where the engraving happens, the glue melts and doesn't come off with the mask. However, the glue does not bond to the acrylic so it is eaisly removed with a rub of isopropyl alcohol.

engraving image goes here


Cut Settings

Cutting With One Mask

Speed: 12/100

Power: 90/100

Frequency: 5000/5000

Cutting With Two Masks

Speed: 11/100

Power: 90/100

Frequency: 5000/5000

Engraving With One Mask

Speed: 60-90/100

Power: 80/100

Engrave Direction: Bottom-Up*

Image Dithering: Standard

Engraving With No Mask

Speed: 60-90/100

Power: 35/100

Engrave Direction: Bottom-Up*

Image Dithering: Standard

* We engrave bottom up because the vaccum pulls material down. If you engrave top-down then there is a chance that the vaccum will not fully pull material off the acrylic. Then, when the laser tries to engrave, it will hit the material on top and lower the engrave quality.