Every Renishaw probe I have used has had to have the spindle oriented when probing. Otherwise I could not trust the results. Try the probe. It will measure much better than .005. Hth Stuart
On Wed, Feb 27, 2019, 12:58 PM Gene Heskett <ghesk...@shentel.net> wrote: > On Wednesday 27 February 2019 12:16:17 Jon Elson wrote: > > > On 02/27/2019 07:50 AM, Gene Heskett wrote: > > > But repeated measurements require I add about > > > 2 counts to the scale value for every repeated measurement done that > > > way, and I've added around 20 counts trying to catch up. In a 16750 > > > count, 20 is not that much. > > > > This is not a MATH problem. I'm assuming open loop steppers > > here, hope that is what you have. > > yes. > > > If you get a fairly consistent accumulating error every back > > and forth movement, it is likely something to do with timing > > of the step pulses relative to the direction pin. Make sure > > the space between step pulses is in the right sense, so that > > the direction never changes when the step pulse is "true". > > That is the one that will surely foul up many step drivers, > > especially if they are microstepping. > > These are, by 8 I believe. > > > Also, check all > > details of the step timing, pause between step pulses, etc. > > If you don't have detailed specs for your drives, then try > > doubling the step pulse, step space and setup time on the > > direction and see if that helps the problem. > > Ok. > > > Jon > > > I haven't checked with a scope to see if the pulses are right side up, > meaning the opto's are only driven for step time, with a large off time > in between pulses but will. With the 7i76, thats very easily reversible > as it has both polarities of drive available. > > The hole patterns its cutting are round and it takes 12 passes thru the > loop to cut one hole, stopping and digging 8 thou deeper per pass around > the circle. I'd thought of that, which is why I checked them for round > although the pattern in the spoil board might be questionable, its > cherry ATM & tends toward leaving a little fuzz. It doesn't cut as clean > as mahogany. > > But I'll double check with a scope yet this afternoon. The drivers are > the original 2M542's, step and space are 1750ns, setup and holds at > 4000ns. Thats some longer in each case than what I've found for that > driver. All 4 are running with that timing. Getting a solid 5 volts on > the + and the -signal for on time from the 7i76 on its - terminal. > > Its crowded up there though as the garage door motor impinges on the > space on the overhead shelf where everything but the coolant tank > resides. > > I should also comment that a g0x0.000000 always ends up at 0.000xx when I > do that, then grab the moving caliper and slide it back against the side > of the tool, with the xx often less than 10. > > Far more accurately than this renishaw clone can do. I find in the spec > sheet its a .005" device. Thats so discouraging I haven't even mounted > it. I'd assume one measures the ball, and figures in half the ball > diameter plus a fudge of 2 to 4 as its true trip point. Piece of junk > IOW. Not at all concentric as it recommends locking the spindle to use > it. Moronic waste of money on my part. > > Thanks Jon. I'll go fix the missus some lunch and get to it. > > 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-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers > _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
