On Thursday 24 January 2019 23:06:40 Gene Heskett wrote: > On Thursday 24 January 2019 21:52:23 Jon Elson wrote: > > 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). > > > > This would indicate the Volts/Hz ratio is not set right. > > This might make the spindle accelerate better, but if set up > > properly, you should not see excessive current at low > > speeds. Some drives have multiple breakpoints, so the V/Hz > > curve can have multiple slopes between those points. > > > > We have a really off-brand mill at work that has an 18000 > > RPM spindle. You can run it all day at 1000 RPM with no > > heating. It really lacks torque at all speeds, obviously > > designed for high speed, but won't burn anything up. > > > > Jon > > I found some programing info that made it work, but just one more > problem leads to another and I'm beginning to wonder if I'll ever find > the last one. I hadn't noticed it was running backwards, and that > wiring was 100% OEM. So tonight I opened the box again to reverse two > of the motor wires. But while in there I decided to put the box on a > diet as its about 40 lbs. So I got rid of the 4 TB6560 drivers, and a > surprisingly heavy power supply that ran them, leaving just the vfd, > the breakout, and a smallish fan. Got it all back together and found > the fan was quiet. Seems it was plugged into the BoB which was plugged > into the PSU I took out. Ooops! The PSU I took out must have been > running in foldback as it was making 14 volts when I checked it with > all steppers powered up, but it was marked 24 volts at not enough > current for 4 steppers when I finally uncovered the label. So I gave > up for the night, not finding a psu to run the fan with. I have some > boosters on order, and a small 5 volt supply I can put back in it to > run the booster to get something like 25 volts to run the fan. Then > see if I can make reverse work, once I get it turning the right > direction. Theres a couple registers in it that might control that, or > I may have to fiddle with my hal. It clearly has a control terminal > labeled REV so I am determined to make it work. > > The right sized 4mm mills came in today, so once it spins the right > direction, I'll go get me a spoil board and carve the panels for 2 new > control boxes. Then I'll have enough I/O to put some home and limit > switches on it. > > Mechanically this machine is very solid, backlash a thou or less, and > with 28 solid volts for the motors, is easily running 100 ipm for > rapids. And this is with software stepping! I think I'm going to like > it except for the 3" Z range. I'd like 6 so I could do some real > carving... > > Thanks Jon.
Currently running it in manual mode, so I practiced on the spoil board. finding the actual cuts were oversized by using G42 when I should have been using g41. But that seems to expose a problem when the circular cut its to make, is smaller than the tool diameter. All I want to do is drive the tool to drill a hole around 30 thou bigger than the tool. What I wanted was a climb, or "chopping into" cut all the way around. Why can't I drill a .209" diameter hole with a 4mm (.157") tool? ===================================== I've about give up on controlling this VFD with a pwmgen directly as I have no way to step the 5 volt pwm up to a 10 volt pwm. Its obvious the thing needs 10 volt signals and logic level stuffs just won't cut it, so I've rummaged around and found an old, old cnc4pc C41 board. It looks as if I might be able to make it work. I'll see what I can hack up tomorrow but I wish I had the OEM docs, cnc4pc has replaced it with a new C41s and I doubt its exactly the same. This one develops the FWD signal, relay isolated, from the presence of the PWM, so has only a 3 wire control, ground, pwm, and reverse which is also relay isolated. And looks to have 2 places where +10, or +12 can be applied, but the - legs aren't common. So I'd better rummage in the shop and see if I can find the original printouts. Progress, but frustatingly slowly. Now why can't I drill that hole? 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
