Update: I've combined my fix for Issue 68 <https://github.com/LinuxCNC/linuxcnc/issues/68> with the jitter improvement in this branch (also pushed to the official repo for the buildbot):
https://github.com/robEllenberg/linuxcnc-mirror/tree/feature/nominal-vel-during-sync This branch also adds a canon-level warning if the user tries to start a G33 move that isn't capable of reaching the required feed. Unfortunately, the warning only appears when the motion starts, but it's better than nothing. Together, these fixes should resolve issue 68 without any backwards-incompatible changes to the 2.7 TP. -Rob On Mon, Sep 26, 2016 at 10:32 AM Gene Heskett <[email protected]> wrote: > On Monday 26 September 2016 08:22:23 Robert Ellenberg wrote: > > > Hi Kirk, > > > > The best way to compare would be Z acceleration. It's easy to add to > > the HAL file (needs an extra differentiator). Then, we can look > > directly at the magnitudes of acceleration. Lower amplitude = less > > jitter. > > > > On a slight tangent what do you think of adding a warning / error if > > the TP can't reach the requested feed in G33 moves? It seems that if > > you're doing threading, close enough is not good enough in terms of > > tracking. The user might want to know before they cut that the spindle > > speed or feed / rev is too high. > > > Field report: > > I actually ran into this on my G0704 when I had that 1600oz/in motor on > the Z. Because the tap in the spindle was a 1/2" 13 tpi, I had visions > of doing a peck tap that was a small enough peck that the stored energy > in the 800 rpm spindle would contribute to the cutting. But that 800 > exceeded the Z maxvel with that motor which was around 28 IPM. So I had > to slow it down. At 400 the tap slipped after about 3/4 turn into the > work, which I caught, backed it out and put a tap handle on the tap & > finished the hole by hand. > > That was when I questioned the list for a tap holder that would grab the > square butt of the tap, but even in R8, which is keyed to the spindle, I > was not able to source a tap holder I could afford. All north of a 100$ > bill and to cover all the taps I might use I would have blown a kilobuck > or more. > > I even knocked the T handle out of a hand tapper that looked promising, > but it was, when chucked up, about 5mm's out of plumb with its own > knurled nut on the other end. So bad I never put a tap in it, I'd have > broken the tap pushing it into line with the hole. The pick any 2 rule > hard at work... > > Even with Jon Elson's driver making a horse and a half, maybe 2 out of > that 1 horse, the spindles low gear still couldn't turn that tap > steadily to the bottom of the hole, not enough geardown. 800 revs was > about 55% of wide open in low gear. Its about a 2/1 gearchange, and the > motor rated at 1 hp at 2250 revs stock in high gear when driven by the > OEM driver, can be driven to 2850 with a 126 volt dc supply which is > current limited in the amp setup to about 16 amps. How many hp is that? > > And yes, I do recognize the singing when it limits. Even TLM does it at > startup. The gears in the G0704's head seem to be holding, but the > roller skate bearings in the head are destroying their ball cages. I am > hoping it hangs in there till I get this Sheldon working. :( That lack > of turn a tap torque is why the new brass gib on the front of the > Sheldon saddle will have a row of 4mm cap screws holding it. The saddle > castings front edge is not IMO, robust enough to do that job if > perforated for a row of 1/4" cap screws. So I figure a 4mm cap screw > about every 2 cm is about what the Dr. would order. It will need a few > thou of shimming. That I can cut from what Ed Nisley was nice enough to > send me, and punch the bolt holes with a paper punch. > > Thanks Robert. > > [...] > > 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-developers > ------------------------------------------------------------------------------ _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
