As you can see it has nice clean edges and it measures 34.07mm by 60.02mm by my cheap electronic calipers so is pretty accurate.
Getting the feed rate and cut depth right took a few attempts. The problem was that the plastic kept melting as you can see here :-
I found that with a cut depth of 0.5mm I could only feed at about 0.2mm per second to prevent melting. Reducing the cut depth to 0.1mm allowed me to increase the feed to 10mm per second which is ten times more productive. I probably could have pushed it further but I am not particularly interested in making anything from this material. Here is a video of the test :-
I now have a small but highly accurate CNC milling machine. A few improvements are definitely needed :-
- Dust extraction!
- Tool height detector
- Spindle motor control and stall detect