On Friday, September 30, 2011 12:30:55 AM Martin Patton did opine: > > Martin, > > I have been using CamBam for 7 of 40 trials. I am amazed at how easy it > is to use so far. > I drew a mount for a stepper motor that has a cutout profile with tabs, > a pocket for the rim of the stepper and four spiral holes sized for > tapping 10-32. With all this advice, I already cut a part in plastic > that fits the motor. > > Jon, > > That is good advice too. I will look for backlash. How do I make it go > awayif I find it? The mill is a Taig. > Generally, 2 places to look, but I'm not a taig owner, mine is the small HF. First is end play in the screw mounts, with the handle retainer being the usual method of adjusting that clearance, but if there are no bearings you need to leave about a thou clearance there. I found some thin ball thrust washers, so mine are slightly preloaded & playless now.
Second is the nut the screw is turning in, and in the economy stuff it is usually a long, lots of threads nut that is sawn nearly through, and either cap screws to pull the saw slot together, or jack screws to split the saw slot even wider. Generally, getting that slop down to 3 thou won't last too long due to wear, but if you keep jacking on the screws it will eventually wear in and can be set at maybe 2 thou without binding. Emc has backlash comp settings that if you stay on top of the wear, can cut bearing pockets that are quite close to round, half a thou is not a lot of trouble. To get closer, one has to go to ball screws, which can be backlash free at normal loading. But those will be $200-500 a copy. > Thanks, > > marty > > > 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 of the data generated in your IT infrastructure is seriously > valuable. Why? It contains a definitive record of application > performance, security threats, fraudulent activity, and more. Splunk > takes this data and makes sense of it. IT sense. And common sense. > http://p.sf.net/sfu/splunk-d2dcopy2 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) The most difficult thing in the world is to know how to do a thing and to watch someone else doing it wrong, without commenting. -- T.H. White ------------------------------------------------------------------------------ All of the data generated in your IT infrastructure is seriously valuable. Why? It contains a definitive record of application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-d2dcopy2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
