On Thursday 24 January 2019 08:41:47 Todd Zuercher wrote: > I have a fair amount of experience with high speed spindles. And I've > found that most are incapable of running much below about 1/3 of their > rated speed for any length of time, and cutting anything at those > speeds is certainly out of the question. If you don't believe me, > start your 18k rpm spindle at 4000rpm and then check the current > readout display on the VFD, and you will be shocked at what numbers > you see displayed (I'd venture a guess that it would be close to about > 200% of rated amps on the motor name plate). > There should be a register in the vfd's configuration to control that, there is in my $90 1.5 horse clone I'm running the 1 hp 3 phase Sheldons spindle with. I can set the maximum delivered current to the motor at 3.9 amps per phase, its nameplate full load amperage. With the vfd, I'm generally working with the 4 speed belt in the 1st or 2nd gear, which gives me chuck rpms from about 25 up to 900 or so. All without causeing excess heat in the motor.
IMO, there is no excuse for burning up a motor with a vfd. And yes there are times when I do bang it pretty hard. I can and have rigid tapped with it, provided I compensate for the overshoot while its getting an 8" chuck turned around from 300 revs fwd to 300 revs reversed. Overshoot can be in excess of 4 turns. But I also have some hal trickery to let me cut air ahead of time, measure the overshoot and convert that into a reduced depth of tap. It gets expen$ive to run the tap into the buttom of the hole and break it, then I have to EDM the remains of the tap from the hole, which with my primitive EDM setup can take seversal hours, so I take countermeasures. You, if you didn't see it hanging on a post above the headstock on that old Sheldon and didn't notice the drum switch was missing, would never guess theres a vfd running that spindle, there is no tell tale 30 seconds to speed, the dead giveaway of a vfd that has never been programmed since it was pulled from the shipping box. I can type s1000m3enter on that Sheldon's keyboard and by the time I can move my eyes to the screen tach, its up to at least 900 revs if in 2nd gear at the belts underneath. That motor has a large inductance, so the vfd looses it due to magnetic slip because of low coil currents at around 200HZ, under an amp a coil at that speed. The only way to fix that is more voltage, like 500 instead of 250 single phase. But thats also stressing the varnish in a 50 yo motor, which never imagined it would ever be run by a vfd since they were invented 40 years after those motors were born. I got 2 of them from an old air compressor for a $50 bill. Put the quieter one in the Sheldon, bought bearings for both, so I've a spare with fresh bearings for the Sheldon and a set in the drawer. $28 for the 4 bearings brought those two motors to $39 each, hell of a deal. ;-) > Todd Zuercher > P. Graham Dunn Inc. > 630 Henry Street > Dalton, Ohio 44618 > Phone: (330)828-2105ext. 2031 > > -----Original Message----- > From: Gene Heskett <ghesk...@shentel.net> > Sent: Wednesday, January 23, 2019 8:37 PM > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] 1.5 kw vfd in 6040 problems > > On Wednesday 23 January 2019 18:59:44 Mark Wendt wrote: > > Doesn't matter. These high speed spindles are not like the motor you > > have in your Sheldon. They will burn up in a short time if you run > > them too slowly. > > And I'll submit that it takes excess current to burn them up. Control > the current below 50 hz and it will run forever, just don't expect it > to throw swarf in 20 thou thick pieces even in wood. > > I have a 1.5 horse air cooled that running on the vfd now driving the > sheldon, ran it for an hour, then overnight on the table at 20hz. I > could easily lay my hand on it the next morning. But I also had the > torque boost at 1.1, and the max current set to about 3 amps. Neither > it nor the vfd was making worrysome heat. > > > But, it's your stuff. If you're willing to take the the very real > > chance of either burning up your high speed spindle or destroying > > the VFD by inputting incorrect parameters, by all means have at it. > > Been a moderator on CNCZone for a good number of years and have seen > > many folks in the spindle/VFD forum who've done just that because > > they figured just any old setting would do or they tried to run > > their spindle too slow. > > I've seen rec's that 6k revs s/b the minimum. I have aquarium lcd > thermometers on the water tank and motor, and one on the driver box, > but before I can log temps vs speeds, I've got to make it spin. > > > Mark > > > > On Wed, Jan 23, 2019, 18:18 Gene Heskett <ghesk...@shentel.net wrote: > > > On Wednesday 23 January 2019 17:48:20 Mark Wendt wrote: > > > > And the data plate from the motor. Incorrect settings in the VFD > > > > can and will result in the destruction of either the VFD or the > > > > motor or both. The settings are quite specific to the motor > > > > ratings. Running the motor slower than 6000 to 8000 RPM's will > > > > burn up the motor if it's a high speed spindle. You can run a > > > > water cooled spindle slower than an air cooled spindle but not > > > > by much before the windings burn out. > > > > > > > > Incorrect settings on other VFD parameters can and will destroy > > > > the VFD. The manual is quite important to have setting the VFD > > > > up and you shouldn't try to power the spindle up without the > > > > correct settings programed into the VFD. > > > > > > > > Mark > > > > > > This seems to be defaulted to quite conservative settings. With > > > the low speed boost backed off, default is 4 and probably too > > > much, it should be able to run slower than that by quite a bit. I > > > can run the 1hp in my sheldon at 10hz for an hour or more without > > > getting so warm I can't lay a hand on it. I never exceed the > > > nameplate fla of a motor at any speed. It will get warm, but the > > > torque seems to hold up well enough to cut steel. > > Thanks Mark. > > > > > On Wed, Jan 23, 2019, 17:33 andy pugh <bodge...@gmail.com wrote: > > > > > On Wed, 23 Jan 2019 at 22:27, Gene Heskett > > > > > <ghesk...@shentel.net> > > > > > > wrote: > > > > > > Many thanks for any clues from someone WHO HAS ACTUALLY DONE > > > > > > this. > > 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-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > 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) 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
