Gene, This tool will allow you to check the relative square of a machine tool.
https://www.travers.com/cylindrical-square/p/57-020-263/ On Mon, May 11, 2020, 2:45 PM Chris Albertson <[email protected]> wrote: > Mathematically, you don't need an absolute reference. If you have a > perfect mill it would still be a perfect mill if put in on a slanted > floor. What matters is the relative angles of the axis. > > Yes we can mesure these angles with inexpensive tools assuming you > have one "good" larger size square you can trust. Those cheap > inductive distance sensors on eBay have sub-micron repeatibilities. > They are intended for use as non-contact limit switches and they work > well for that. If you put one in a chuck facing down you can detect > axis tilt. In fact, you do the same with a dial indictor, Then you > scan the sides of your "good" steel square. to detect z-axis tilt. > > What the system would do is do a scan and see the error. Then it > would compute what compensation is required and does the scan again. > This way it sees that moving in X or Y no longer effects Z. > > But there is nothing you can do about tool orientation. Drills and > fly cutters can not be fixed but the system could report the angle you > would whack it with a mallet then re-test. > > On Mon, May 11, 2020 at 11:52 AM Gene Heskett <[email protected]> > wrote: > > > > On Monday 11 May 2020 14:22:26 Chris Albertson wrote: > > > > > So, lets say I have a machine that has non-tricial kinematics (I mill > > > with the z-axis tilted 30 degrees) and I write the kinematics routines > > > correctly. Then you are saying the machine will not honor accel and > > > velocity limits? > > > > > > But all machines are like this, not 30 degress certainly but some > > > number of arcseconds. A nice feature would be to compensate for all > > > the errors, not just the bed. > > > > That then raises the question: What reference point then becomes the one > > true reference? Do we have the reasonably priced tools to measure it? > > For me that answer is no, but I have observed many times that the hole I > > drill by putting the work in the spindle, and a drill straight up from > > the bed, are oviously out of alignment by the time that hole is 1" deep, > > I am bending the drill. This is likely because it was required I remove > > the post while installing the ball screws, and the post is attached to > > the base with horizontal bolts into the rear of the base casting, > > meaning any slop in those boltholes will allow the post to lean left or > > right at least a degree. And it is very noticeable. But, where is the > > square that I can use to loosen those 4 bolts that mount the post to the > > rear of the base casting, and adjust it for plumb? Such a > > _3_ dimensional square isn't for sale that I know of. > > > > > I would not be surprised if non-trivial kinematics is broken as so few > > > people have machines with not-square axis the code would not be well > > > tested. That said, te velocity problem is proportional to the cosine > > > of the tilt. It is going to be tiny. > > > > > > On Mon, May 11, 2020 at 11:03 AM andy pugh <[email protected]> wrote: > > > > On Mon, 11 May 2020 at 18:38, Chris Albertson > > <[email protected]> wrote: > > > > > Perhaps kinematics is the place to do the > > > > > bed compensation. > > > > > > > > We tried that with "probekins" and it turned out not to to work very > > > > well. external-offsets seems like a better way as it honours accel > > > > and velocity limits. > > > > > > > > -- > > > > atp > > > > "A motorcycle is a bicycle with a pandemonium attachment and is > > > > designed for the especial use of mechanical geniuses, daredevils and > > > > lunatics." > > > > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > > > > > > > > > > _______________________________________________ > > > > 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 > > > > -- > > Chris Albertson > Redondo Beach, California > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
