On Tuesday 29 June 2021 18:28:13 Viesturs Lācis wrote: > Hello! > > I have a question about a machine that I converted to LinuxCNC 5 or 6 > years ago. It is a 4 axis mill that is used for making jewelry - > milling wax parts that are then turned into nice things with lost-wax > technique. > > The issue is that Z axis is losing height. That is best observed, when > the milling is done with rotary head. Here is an example - the height > difference of first passes vs last passes is approximately 1 mm: > https://www.picpasteplus.com/v.php?i=507b0d6be4 > > The thing is that the client told me about this problem few years ago, > but then it somehow disappeared or at least the position error was not > that huge and it was possible to fix the wax part before proceeding. > > Machine is running 2.7.4 version. Here are the INI and HAL files: > https://pastebin.com/N7tk8nnW > https://pastebin.com/epyUVbpp > > I am convinced that all the possible mechanical causes have been > checked. For the final check, we brought Z axis to particular > position, marked motor shaft placement regarding motor case, then did > the milling and afterwards brought it back to the same position - > marks on motor shaft _did not_ match the case. > > I changed the feedrate and acceleration values 2x lower just to make > sure that machine was not missing steps. Or is it still missing steps? > > So I would like to ask for some ideas, what else should I try and > where to look. > > Viesturs > I have not looked at your files so I don't know if servo's or steppers are in use. If steppers, I would make the assumption that dir-setup and dir-hold needed more, you are losing one step every time the direction changes, but only in one direction. So add half a u-sec to DIRSETUP and DIRHOLD to see if that fixes it.
Take care Viesters. > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
