On Thursday 23 July 2020 01:57:46 John Dammeyer wrote: > Hi Chris, > > > -----Original Message----- > > From: Chris Albertson [mailto:albertson.ch...@gmail.com] > > > > Why on Earth do people still use US units? OK if your final result > > must be expressed that way, but do the math in metric then convert > > at the end. > > <SNIP> > > > I taught high school science for a while and never once would ever > > talk about US units like feet or pints or pounds. The students had > > no problems with this as their middle school teachers did the same. > > No one who is educated in the last few decades would know how to > > work with "feet per second squared" > > Appreciate the comments. But even if I used the servo motor 1.6Nm the > pitch of the lead screw is 0.2" so I could easily convert that to > 5.08mm or 0.00508m for that matter. In Canada much of what we do is > metric. And my program has a check box that lets a user switch along > with converting all the imperial units to metric and back. > > But that's beside the point I think. None of what you said explains > how to calculate the MAX_ACCELERATION in the INI file given parameters > like motor/leadscrew torque, leadscrew pitch, max speed and table > weight (mass). > > Any ideas? > John > I think its difficult, if not impossible, to accurately predict what performance you get just because there are so many variables. Take the x axis of my sheldon as a furinstance. With both axises running on honking big toroid supplies, making about 43 volts in the case of the x axis, it could not move at more than 30 ipm without stalling. Should be unrelated changing the z motor from a 1600 oz/in nema 34 that could move the Z at 72 ipm, on a 65 volt supply, out for a 3 phase, 3NM nema-23 running on a now 42.5 volt switcher, but because of the length of the 7.5 amp switcher, I had to remove both big toroids and install 2 of the 7.5 amp supplies. So x, still running on virtually the same voltage, one would think it would still run the same.
Guess again. I have a new X speed limit of 120 ipm! Actually thats above, but the motor doesn't stall, it trips off the driver decelerating from 120 ipm, but doesn't trip that 2M542 at 110 ipm. The newer 3 phase z driver can now do 120 ipm w/o any problems. The x difference is only the better regulation of the now switchmode supply thats within a volt of the supply removed. So I'll submit that only by building it and trying it, will you find the limits. Accel limits were able to be raised from 3.75 to near 20 at the same time. Results are so good that I may swap the nema-24 in the apron out for a 2NM version of the 3 phase as its short enough to fit whereas the 3NM is about 5mm too long and its rear would hit the bed. OTOH, a 4x improvement in both speed AND accel, just by swapping its power supply was a very pleasant surprise. But I'll put some time on it as is. The main problem with the full 120 ipm movements is that the 2M542's don't have a fault output. So LCNC keeps on blindly sending movements to a faulted driver. Thats not good when it happens, so I'll slow it back down a wee bit. Anyway, have fun finding the limits, stay safe and well, all of you. 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
