On Wednesday 22 February 2017 08:56:08 Valerio Bellizzomi wrote: > On Wed, 2017-02-22 at 08:14 -0500, Gene Heskett wrote: > > On Wednesday 22 February 2017 04:50:20 Valerio Bellizzomi wrote: > > > > Haveing a module processing data from a read above the actual > > > > port read inserts a one loop execution delay in processing that > > > > data, so unless you want a delay on purpose, the order is always > > > > the read at the top of the list, the data massaging in the > > > > middle, and the write of that data is always last in the addf > > > > order. The data twiddling can be a thousand lines below all > > > > this, but it will be executed in the order of the addf's. Delays > > > > in processing, then making use of that data affects the > > > > stability of the loop because the data is stale. Most > > > > noticeable when setting up the PID modules. > > > > > > Thanks Gene for this clarification about LinuxCNC internals > > > > You're most welcome. > > > > [...] > > > > > I'm not accustomed to inches, that should be 40 * 2.54 = 101.6 > > > mm/min > > > > Wrong multiplier, an inch is 25.4 mm's, so 75 ipm=1905mm/minute, > > almost 2 meters a minute. With the right motor instead of this 1600 > > oz clunker I'm useing, I could at least double that. > > That's true, oops, but well, yes the max speed is approx 2000mm/min > > > > with my current machine I can set a speed of up to 800mm/min (when > > > cutting wood) without any problem > > > > Thats about 31.5"/minute. None of my spindles can cut mahogany at > > more than 15"/minute, the spindle is way to slow, and then, since > > its generally 3/4 inches thick wood, I do it in 3 passes to full > > depth. I am fond of the Green and Green joint, a huge box joint > > whose fingers are somewhere between 22 and and 28mm's wide, for > > furniture, and make it on the G0704, including the assembly screw > > holes and the square pockets above those for the ebony buttons that > > hide the screws. I make those on the milling machine too. > > > > But the top speed on its spindle is around 2750 with the cheap > > bearings in the back gearing screaming for mercy. I've got to > > replace them with quality bearings. I don't often run it above 1500 > > in deference to those cheap bearings. > > > > Where on this ball of rock and water are you? > > > > Cheers Valerio Bellizzomi, Gene Heskett > > > > > > Cheers, Gene Heskett > > I can cut wood at 20mm depth at 300 to 500 mm/min > > but the vfd on my pantograph has a manual dial and a Hertz display, so > I don't know the rpm for sure, only the frequency is displayed which I > don't remember now > That motor, since you are cutting wood, is quite likely a "2 pole" motor, which would turn at 3575 revs or so w/o loading when the vfd says 60 hz, and would be turning quite close to 24 thousand rpms at 400 hz. If your vfd can go higher, the motor would speed up to even more rpms, but you'll eventually it a limit, either because the motor explodes or its inductance gets in the way of establishing a strong enough rotating magnetic field and the motor goes into mangetic slippage with almost zero torque to do work.
I'd add a pyvcp tachometer to the axis display, setting its full scale to the motors rated top speed, then feed it with the pwmgen.value input, thru a scale module to make the tach dial match the speed. Thats NOT the feedback obtained from a motor encoder, but if the scale modules gain is set correctly, it should match the motors speed within 1 or 2 percent. If the motors slip angle becomes too great, the vfd may complain, or even stop with an overload message. That equals a damaged project and quite likely a broken tool, obviously to be avoided. If the error message is accompanied by a signal that could be used to exert an e-stop, that is certifiably a Good Thing. My counterfeit vfd that is turning the spindle on this Sheldon 11x26 lathe I am converting, has no such tally output, darn it. Best I could do is compare the command to the vfd with the encoders output velocity, which in the grand scheme of things would also catch bad belt slippage and such, so that may get done. I just need to find a round tuit. I may have to make some of those yet. When I get the time. ;-) Cheers Valerio Bellizzomi, 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> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
