I purchased my mill in May and have intended on contributing back to the forum since then because it helped me so much in my setup and initial research of my 7x12 mill. Unfortunately, the files that I created for this case were done on a 40 day limited version of SolidEdge, so hopefully it can perhaps inspire ideas or improved versions.
I picked up the plastic (acrylic I believe) at a local plastics shop. It was free because they considered the pieces I got to be scraps. I had different thicknesses, so I had to work around that in my design.
This is the side panel where the fan mounts. It is in the process of being milled.
I had some trouble milling the plastic. The bit would heat up and the material being cut would stick to the heated bit. This would create a glob of plastic that would eventually scrape the surface of the plastic along the edges of my cut. I did not remedy this problem to my satisfaction. I simply had to stop the machine to clear the globs occasionally. Vacuuming up the plastic bits occasionally did cause the bit to cool slightly, but I am all ears if anyone has a fix for this. I was milling at about 7000RPM, 400mm/min.
This is the front panel with most of the switches and holes milled.
This is the case partially assembled and the assembled parts drawn in SolidEdge.
I have created a youtube video to show the nearly finished project, and it shows how the parts fit into the case, and where the case will attach to the mill.
Generally with plastic, especially acrylic, faster feedrate and lower spindle speed is best which minimises heat. More passes at less depth will also help. As you may not be able to slow your spindle sufficiently and you are already at max feedrate for standard screws you could try some cooling instead. I built a wall around my cut area with plasticine to for a dam and filled it with water. Alternately you can just stand there and keep spraying it with a water bottle. Not only will you save your bits and plastics, the cuts are so much cleaner.
I look forward to getting things back in working order so I can try out the suggestions. I created the motor speed controller specifically for milling plastic, so hopefully I can get it to work. Now I just need this school semester to end so I can take some guilt free time to do this stuff...
I have since started to use the technique described by 'roller' above using water. I drip beads of water using a syringe to the area being cut to cool the bit. The cutting quality improves tremendously and I no longer require the slower RPM that a spindle speed controller would provide.