I bought a Boss8 R2E3 that already had servos and ballscrews and we have upgraded this machine from the original control to Geckodrives and the Linux EMC software.
We ran the first parts today and I noticed when measuring the finished part it is off from the size listed in the CAD drawing. Its an egg shape that is about 1.5" long and 1" wide at its widest part - just a simple 2D part. The length is off by about .05" and the width is off about .04". The part is oversized by this amount. We were using a speed of 2500rpm and 6ipm feedrate with a 2-flute 1/2" endmill with 1/8" depth of cut per pass. We tried machining the part out of PVC plastic first, and initially thought the error could be caused by shrinkage of the plastic. But then we tried it out of 7075 Aluminum with the same results.
Another interesting thing was that the path the tool followed was measured to be .525 and not the .500 expected. Measuring the tool shows .499 which is pretty dead on, so how come the cut path is off?
Any ideas about what could be causing my parts to be off? I was cutting the Aluminum dry and squirting on WD-40 occasionally to help lube it a little. I dont have the coolant hooked up yet (will do that soon).
Help!