On Saturday 08 September 2018 18:30:42 Chris Albertson wrote: > This has already been done on Merlin. Merlin is the software that > interpret g-code for most 3D printers. > I see, but that also is dealing with what effectively is a plain one dimension rendered in 3d.
A lathe is a slightly different critter, and the major src of the error is the tilting of the carriage in and out due to different amounts of wear front and rear, so the correction consists of moving a dial along the centerline height, and measuring this in and out wobble the tilting creates and applying an in or out correction of 3 thou maximum, so the cutting tool effectively follows a straight line. Due to the wear createing a height of tool motion, its acknowledged but unless working on a eighth inch or smaller part, this height change is surely under 0.001" in effect on the part unless its super teeny. > The way it works is there is a distance sensor on the print head and > it probes the entire bed in a grid pattern. It ALWAYS finds that the > bed is not level and not flat. There are several kinds of probes > sorted. One is a simple microswitch. > > Then after probing the bed and seeing that it is not flat or square > it computers a transformation matrix and then later all X,Y,Z values > in the g-code are transformed. In the end you have a part that is > perpendicular to the bed but maybe not vertical. Depending on where > on the bed your part is it might be leaning in a different direction. > Again, an effect that on a lathe, that is quite miniscule, and with only stepper motors to microstep control, plus the lash in the ball nuts and thrust bearings, is quite low. So low that its a non-problem if not working on the hubble mirror. > It works well within reason. Actual errors need to be only a few > thousands. In my case the bad is slightly bowel shape with the > =center being about 0.2mm deeper than the corners. This level of > error is easily corrected. I assume you meant "bowl" shaped. :) Do we have a receiver/logger module for the digital output of a scale I intended to put on the tailstock barrel, one of Shar's lower cost models with a remote display. This, fed to some math to detect the high and low spots and how high or low which would allow the error to be logged. I could mount it in a tool holder and put a teeny ball bearing to ride the calibration rod, and rubber band its slider toward the rod. Its a thought anyway. I'd have to obtain the data cable, or just log it from its own display every 1/4" if no recording module is available. At least I would have a good starting point, which may in fact be "good enough for the girls I go with". Thanks Chris. > > On Sat, Sep 8, 2018 at 12:23 PM Gene Heskett <ghesk...@shentel.net> wrote: > > Greetings all; > > > > I am about to give up on this bedwear comp project. > > > > How I determine the amount of correction needed has been tried by > > watching the dial as Z is moved, taking notes as to which way the > > center of the wobble (the spindle is running about 15 rpms) moves, > > and putting that DRO's RAD in the hal files lincurve "setp" list. > > Makes it worse, change sign of lincurve y-val, still worse. Seems > > like the correction is being multiplied by 3 or more. > > > > I have run it to a lincurve X-val-nn point, and using the jog dial, > > centered the dials wobble on zero, then put the obtained rad into a > > y-val-nn, again making it worse with either sign. > > > > So how do you folks derive the correction needed? > > > > I'm assuming the offset itself is in radius, not diameter. In which > > case the needed radius correction max's at about 2.5 thou. And that > > the sign is the "tricky" part. > > > > Thanks everybody. > > > > -- > > 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) > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > 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) Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
