PNC-300 CNC mill retrofit - arrival
So I found a Roland PNC-300 mill on eBay. In college, one of my professors had a PNC-3000 in his office, and I always really liked that unit, and the PNC-300 seemed pretty much like a PNC-3000 with the addition of a chip containment cabinet.
So I went for it, and a few days later the unit showed up on my doorstep:
Pretty quickly it turned out that it could cut pretty nicely at level hight with very small depths of cut in soft materials:
But any cut at all that would put load on the spindle, especially in the z axis would cause lots of chatter. Time to take apart the unit and see if something is broken.
It turns out that the whole thing is constructed in a pretty flimsy manner. Instead of ball screws, it is using steel wires.
A quick check with a dial indicator did show that the thing does hold the promised 0.01 mm accuracy - as long as no load is applied. The worst offender is the z axis. Due to the use of a very flimsy linear bearing the z axis can deflect for several millimeters! at the cutter under the application of moderate load with my hand...