Luke,

0.05mm is probably the best you will get without spending megabucks on the actual bearings, preloaded ballscrews with very heavy preload and loads of tweeking and an autolubrication system. Just for your information, if you were to ask 0.05mm tolerances on a drawing sent for RFQ on a milled part, you may be shocked at the price difference it will have compared to a 0.1mm tolerance.


You will also be losing motion in the actual friction of the machine. Have you installed and autolubrication system yet?

When you did the circle test, did you do roughing and then a finishing pass or two? Small endmills may introduce some issues too so you get around that with a finishing pass that is easier on both cutter and machine.

Finally, how did you calibrate the x and y steps/unit? DRO? measurements or based on the 200 steps per revolution and screw's pitch.

Another thing to note is that you probably have C7 accuracy ballscrews if I read Damien's site correctly. These cannot be preloaded evenly throughout their travel. They are rolled and have an error allowance of 0.05mm/300mm of travel. The price goes up exponentially with accuracy of course.

So your best bet is to fiddle with the backlash compensation of the CNC program you are using (MAch/EMC) and be happy with what you have. You will definitely be hitting the limits of the machines accuracy too. I had my Chester Superlux re-scraped it was so out.

Feel free to drop me a line if you need more detailed help.

George