My take on a stepper damper

[Jay C]

Corrie, you should understand the manner in which this device helps and then you can answer your own question. You will also need to be more specific on how you would modify the puck.

[corrie]

I,ll be honest I don,t realy know how or why a stepper motor stalls out when doing a rappid move.One day all is fine and on some other days not so good, whats the difference from one to the other? The problem was in the X AXIS, I set the acceleration from 90 inches a min to 70 and it seems fine. But now when a program has finished it,s run and returns to start point it is slightly off buy a few 32nds in both the X and Y. Going back to the puck, I thought that a puck would have some benifits due to the density, plus it,s easy to machine. Maybe you could rout out a circular chanel and put in a raceway with small bearings as one had mentioned before, like I said don,t realy know about how steppers and low band frequencies.

[Jay C]

Corrie,

I don't think your issue is resonance, I think you might have your acceleration set too high and there might even be a mechanical issue of a high spot on your ways. Also, if you are off, then it could be:
1. Backlash
2. Missed steps
3. A tumor (in Arnold's voice)

Jay

[barryc]

I have recently been battling with some bad mid range resonance on my x3 mill. I am using a Xylotex 4 axis drive with 425 oz steppers. I had reduced the resonance by greatly reducing the Vref on the drive. However this is a very poor fix as it hurts performance. I looked at several damper designs used on engines. Elastomer, fluid and a pendulum type. I decided a pendulum type might offer the quickest response and be able to absorb a wider frequency range so I gave it a shot. The results are nothing short of amazing. It completely absorbs all resonance and vibration problems I was having. I was able to turn up the Vref to full power without a trace of resonance with the damper installed. Remove it and the ugly resonance is back. It's dramatic how well this damper works. TCI makes a automotive type of this damper for racing and they call it the "rattler". This is because when it is working you can hear the rollers working. It's very interesting to hear this damper work. At feeds where there was usually resonance the damper will be very active with the rollers making noise while they are absorbing the resonance. At speeds when the stepper is in a resonance free operating range it is dead silent. It's easy to make. My design is about 2.45 in diameter with 9 rollers.The rollers have .045 clearance in the pockets. http://i109.photobucket.com/albums/n...rdamper001.jpg http://i109.photobucket.com/albums/n...rdamper002.jpg http://i109.photobucket.com/albums/n...rdamper003.jpg http://i109.photobucket.com/albums/n...rdamper004.jpg Steve

Steve, This looks great and I am about to start making two. I note the rollers are steel, is the body of steel too, or aluminium? Regards, Barry

[Fixittt]

The body can be anything that is handy. Wood, Plastic, aluminum ect.
Remember these things rattle. That is HOW they work. So alloy on alloy is going to make ALOT of noise!

I used delrin for the body of mine. My only problem is that where the set screw screws onto the stepper shaft, this hole gets stretched a bit and the set screws loosened. I switched to allen bolts and used RED locktite on the bolts. So far so good. Issue seems to be solved

[grahamshere]

Hi every one. I was wondering if the dampners rattle while the motor spins, I made some with derlin and used 3/8 bearings, the dampner is 2.5" dia but they dont rattle and the dont make any difference on my machine , im still getting resonance, atleast I think its that,
I ran the motors off the table and they run around 90 ipm or higher but at the odd time they stall, then i put them back on and run them with just the lead screws no gantery and all im getting is 30 to 40 ipm they just sit and whine, no torque at all, Any help would be greatfull. Graham

[Jay C]

First: what size are they, how are they wired, what is your driver (who makes it and what step is it set for), what voltage are you running them at, and what current is you driver at?

There are a lot of variables that can lead to stall. However, as in the previous case I believe your acceleration is set too high and you are experiencing magnetic "slip". This is especially true when you are running them "off" the machine and they still sit and whine. BTW, when they are whining like that, that the switching frequency of the driver you are hearing. Unfortunately if you let it go on too long you run the risk of turning your motors into heaters and demagnetizing the rotor magnets.

FWIW,
Jay

[grahamshere]

Hey jay thanks for the reply. Im running Xylotex 425,s. there on microstep, ive played with the acceleration from 1 to 20 and that made no difference. I think my volts are at 30 . do you think that may be to high?What do you mean what is my current? do you mean verf?That im not to sure ,3.5 I beleive. If you know what a good set up for these motors im all ears, my lead screws are 1/2" acme screws 10 tpi, my goal is 60 to 80 ipm with this machine, ive had it running 80 ipm then it would stall and reck my carvings. thanks for your help. Graham

[Jay C]

Hey jay thanks for the reply. Im running Xylotex 425,s. there on microstep, ive played with the acceleration from 1 to 20 and that made no difference. I think my volts are at 30 . do you think that may be to high?What do you mean what is my current? do you mean verf?That im not to sure ,3.5 I beleive. If you know what a good set up for these motors im all ears, my lead screws are 1/2" acme screws 10 tpi, my goal is 60 to 80 ipm with this machine, ive had it running 80 ipm then it would stall and reck my carvings. thanks for your help. Graham

OK, you have the Xylotex 3-axis kit. The motors are bipolar and have 425oz-in holding torque. Your power supply is 24VAC at 5A. Is it safe to assume Mach as the software? If so, what are your motor tuning settings? What concerns me is that you said the motors would stall when they weren't connected tot he machine. The only causes I can think of are:

1. Bad driver or motor (does it only happen to one motor)
2. Bad wiring (same question as above)
3. Acceleration set too high

Since we said it makes no difference what the acceleration is set to I need to ask where you are setting your acceleration? It should make quite a difference when you drop acceleration from 20 to 1. You can PM me or we should take this to a new thread as I don't want to hijack this one.
Jay

[grahamshere]

Thanks Jay, Im using mach 3 the setting are 1600 steps per, velocity is 40 and acc I tried from 1 to 20 step pulse at 0 same as dir pulse but have tried them up to 5 and no difference, with the motors off the machine it happens to all motors but 1 is worse, if I hold it it stops but if I tilt the motor around it happens, Im thinking it could be my verf set too high , im sure its at 3.5 and also resonance is playing a roll in it as well. My wiring is correct as to the diagram that comes with the drivers. When setting the verf do the wires have to be disconected from the driver or just unpluging the power work ok?
Thanks Jay. Graham

[Buzz9075]

This happened to me on two of my motors. I proved it was not mach 3 by switching up witch motor the axis was spinning. So lets say X axis is spinning motor number one and it stalls. Change mach3 to spin motor number two, three or four and if it does stall then you are sure its not mach3. This I did and mach3 was not the problem... So I looked inside the box and the heat sinks were loose, even a little loose or dirty will cause a problem. NOTE: DONT TWIST THE SINKS HARD do it softly to see if they are loose, you don't want to make a perfectly good sink bad.

Best of luck.

[grahamshere]

Hey buzz, thanks. Didnt you put dampners on your motors? I was up last night reading your thread about the problems you had, sounds simular as mine as do a few others ive noticed on here. on the videos that some showen the motors with out dampners sound like mine . Graham

[Fixittt]

when you made your dampeners. Did you make the hole for the bearings .015 to .020 bigger then the bearings you put in?

They should rattle a little bit when stitching direction but not much. Remember you have centrifugal force when the motors are spinning.

If your still loosing steps then back down your velocity and accel.

V refs for the first gen ver 4 boards are 3.5 MAX Need to have cooling fans with this.

Like was said above. Many things come into play with lost steps.
here ar the vids I made of my setup and the horrid harmonics.

[ame]http://www.youtube.com/watch?v=9RoOZs9LrYo

[ame]http://www.youtube.com/watch?v=ivDQTeGuduk

[ame]http://www.youtube.com/watch?v=8Am69_F93yA

[grahamshere]

Hi fixitt, Turns out my verf was way too hight, I had an old dial multimeter that didnt work well, My verfs were like 3.7 so that was my problem, now there at 3.6 which is the max for my board. I have 2 motors running at 50 ipm with out looing steps or torque but one I cant get past 25 ipm even off the table so im not sure whats up with that. Hoping I didnt bugger anything up. Graham

[grahamshere]

I meant to say thanks for the vid,s as well and I also meant to say I cant get past 25 ipm then I lose torque. Graham

[Jay C]

Graham, You could have fried the driver for that axis. Test a known working motor on that driver to confirm ... also as a cross check, put the 1 motor in question on a different axis to test that it's not the issue.

Jay

[grahamshere]

Hey jayc, I bet thats what I did, Ill check in the morning to see if I fried it, man thats going to be a bugger if I did. Im sure xylotex can fix it but how long, even 2 week will be a pain, im so close to start working. crap, oh well see in the morn. Graham

[Fixittt]

The faster a stepper motor spins the less torque it has.
With my maxnc I wanted 40 IPM BAD when I first started this. But it would just act stupid.
Granted I couldnt even cut wax at that speed, it was all a mind thing. I finally tuned everything and I am totally stable at 22 IPM and my wax looks great.
I would much rather cut the wax 1 time at 22 ipm rather then try to go faster and waste more time when the machine messes up. Granted with doing jewelry I have thousands of moves that are really small. My average g-code size is 8 megs. Alot of movements!

If it were me, I would back your V refs down to 3.5 or even 3.3 This is because when a stepper is not under power, it becomes a generator and pushes power back thru the board. So give yourself a bit of head room. You dont want to be sitting on the jagged edge of blowing something up. Driver boards are not cheap and its not worth the potential dangers.

Also a stepper will preform worse just sitting on a bench. It needs to have a bit of weight on it to function properly. Do not rely on a testing method that doesnt have force or drag on a stepper motor.

Ohh and when you find a setting in mach3 that is solid. not missing any steps ect. But if you go any higher or faster it starts acting stupid, back the motor tuning down 15 to 20 % from that setting.

[grahamshere]

Hey fixitt, im testing one of my drivers today but I think its buggerd , If I lower my verf any lower than 3.6 like say 3.4 I only get 10 ipm so im sure its toast. Its because I used a crappy multimeter, was giving me a bad reading, I should have realised somthing was wrong when the motors got hot but I thought that was normal, now they stay warm not hot. Stupid me I guess,Leason learnt as they say. Oh by the way im useing acme screws 10 tpi so I should get better than 22 ipm so jeff from xylotex says.Graham

[grahamshere]

Hey guys, Well turns out its my motor, I swapped the axis around and its the motor thats causing the problems, might try and swap the x with the z if you know what I mean till I buy another motor off Jeff. Graham