Martin Patton wrote: > Hi EMC users, > I have EMC running on an old pc, latency number about 25000. I got an > occasional real time error with latency number set at 22000. > I drew a part in CamBam, generated some g-code and cut a part. The part > looked right but the caliper says every dimension cut a little small. A > circle pocket drawn 1.50 diameter cut about 1.42 in diameter, The tool > diameter matched the tool specified in the cad program. Is there a good post > on calibrating for a stepper motor machine? > First, you need to measure the actual movements with some kind of measuring tool, even if it is just using a dial caliper. You need to separate linear movement error, backlash and tool deflection. Without separating these different error mechanisms, you will not make the right correction. Linear error is pretty easy, put a pin in the spindle and measure between it and a block fixed to the table. If you move in the same direction, backlash will not alter the reading. Moving a number of inches so as to use nearly the full range of the caliper will give the most informative result.
Then, approach the same coordinate from both directions and measure position. This may be harder to do with a caliper, as hopefully your backlash is relatively small. It is best to do this with a tenth-reading dial test indicator, if you have or can borrow one. Backlash alone could cause the error you report above. It will also leave 4 steps in the walls of a circular pocket, at those places where the axis needs to reverse, but takes a moment before the linear motion picks up on the other side of the backlash. If your problem is backlash, these steps should be really obvious on the part you mention above. Finally, it could be tool deflection, which will cause milled pockets to come out small. (Your measurement above seems to big to be tool deflection, however.) But, tool deflection will NOT leave bumps in the wall like backlash. Jon ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
