Need Help!- Backlash

[rodzilla]

O.K. i changed this weekend from a single ballnut to a preloaded ballnut and my problem with moving axis 1", 2" 3" etc.. cleared up i am now using 10000 steps per in Mach3 and if i move the axis 1-5" i am getting either right on the money or +/-.001. My problem is when cutting an actual part if i cut a circular pocket it will come out .005 - .010 smaller than it should i also get the same problem with profile cutting circles, squares, etc.. Do you guys think that i don't have enough preload on the bearings should i add more disk springs in to make the load heavier

[philbur]

Have you checked your cutter size. Have you checked the run-out on the cutter. Is the "circular" pocket circular or can you actually see backlash in the part at the point of axis direction reversal.

Phil

Originally Posted by rodzilla O.K. i changed this weekend from a single ballnut to a preloaded ballnut and my problem with moving axis 1", 2" 3" etc.. cleared up i am now using 10000 steps per in Mach3 and if i move the axis 1-5" i am getting either right on the money or +/-.001. My problem is when cutting an actual part if i cut a circular pocket it will come out .005 - .010 smaller than it should i also get the same problem with profile cutting circles, squares, etc.. Do you guys think that i don't have enough preload on the bearings should i add more disk springs in to make the load heavier

[rodzilla]

The cutter size is correct. What do you mean by runout on the cutter, I can't see signs of backlash in the circular pocket

[LongRat]

Phil is talking about the cutter not rotating true. You might have play in your spindle bearings, for example. Check their preload. Also check for tightness of your z-axis gibs. Any slack here could cause your head to move when taing a cut, or plunging up or down. Alternatively, your machine may not be of sufficient rigidity to hold those tolerances under load - you are getting elastic push-off. The solution here is to try a spring cut: simply run the same path again as a second pass, and see if the situation is improved.

[rodzilla]

O.K. i will try that I am running a HF 33686 Mill same as the Ronfu round column mills that other people are using and they are saying that they get good results with this setup i'm just trying to figure out where i am going wrong thank for your help guys