Wendy asked me long ago if I could make a sign for her family farmhouse. I bought some plastic sign material almost a year ago from Trotec at engraving-supplies.ca but never got around to making the sign. Well, I corrected that today.
The sign as it came off the CNC machine
I had made a small name sign on a piece of scrap 2-colour plastic I had laying around so I was pretty sure that my feeds and speeds were good. When milling plastic, the thing to avoid is going too slow. If you do, the plastic will melt on the bit.
So I used a 1/8 inch single flute upcut bit with a feed rate of 500 mm/min which is about double my normal feed speed for wood. I also took a deeper per pass than normal because of the softer plastic material. I cut the design to a depth of 0.6 mm in a single pass into the 1/8 inch (3.175 mm) material. These settings seemed to work well as I made lots of plastic chips and no melting.
The sign presented a challenge because at approx. 300 x 300 mm, it was twice as large as the work are on my 3018 PROVer (280 x 165 mm). The design had to be split into two separate carves, each of which being within the limits of my machine. After carving the top half of the sign, I repositioned it on the bed and cut the bottom half. The piece was held down with double-sided tape as it was too big for me to clamp it. Man, that tape really holds! I was worried I might break it prying it off the tape, but I was careful and successful.
I have a happy customer with this one!