On 08/06/2013 10:25 AM, andy pugh wrote: > I am in discussion with a chap who is retrofiting a Hardinge HXL. It > has linear scales, interpolator boxes set to 256x and is running a > 5i25/7i77 combo. > > The repeatability is good. Actually is is better than good, it returns > to the exact same digit on a 0.1um (0.000004") length probe every > time. > http://youtu.be/2oWc6val6ME > > The problem is that the travel distance isn't accurate. A 50mm move is > out by 0.158mm. The encoder scale is set to 25600 (10um scales, 256 > interpolation). > It doesn't seem like it could be missed encoder counts or the > repeatability wouldn't be so good. > > Any ideas where to look? Bear in mind that this is all done by linear scales. > cosine err? the motion of the axis must be colinear with the motion of the scale theres a few pages supplied wiht all Heidenhain scales describing the mounting techniques and qualifications. i could assume this has been verified, but it would explain motion that returns to same point yet has constant distance err regards tomp
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