Years ago when with my first homemade CNC that used leadscrews I found that I could get better results if after cutting the circle I then cut it again but in the opposite direction. You may get much better results because the cutting forces in the opposite direction will be opposite for each 90 degree segment of the circle.
John Figie --- On Fri, 3/26/10, Jon Elson <[email protected]> wrote: From: Jon Elson <[email protected]> Subject: Re: [Emc-users] accuracy question To: "Chris Reynolds" <[email protected]>, "Enhanced Machine Controller (EMC)" <[email protected]> Date: Friday, March 26, 2010, 11:22 PM Chris Reynolds wrote: > I have a quick question that I'm sure will be simple for one of the members > out there. I've been using emc now for about a year and I'm now running it on > my milling machine. I've got backlash set in the .ini file but I've noticed > now that when I'm cutting around a circle that it's not coming out > accurately. It's as if the motor when it changes direction while cutting a > curve or circle speeds up to take care of the backlash, but then what's > happening is that my cuts aren't coming out perfectly round. Any suggestions? > Yes, this is one of the N reasons that backlash compensation really doesn't work in any profiling application. It kind of works in hole drilling applications where you don't do anything with multiple axis coordinated moves. The problem is, for the most part, only solved by fixing the backlash. In your case above, every time an axis changes direction, the motor is required to instantly move from one side of the backlash to the other. This requires two instantaneous accelerations, which are of course physically impossible. So, anything the CNC program does is already wrong, attempting to do the impossible in the least awful manner. What is worse is that backlash leaves the table unconstrained by the motor/leadscrew. So, any time the screw is driving the table in one direction, cutting forces could pull the work further into the cutting tool. Just an overall bad situation. Jon ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
