[hub]

I'm new with this stuff so..
I connected everything and started testing with Mach3..
The steppers run fine at about max 500rpm, but stall if I try to go any faster (no load attached to the steppers).
I *think* I have the steppers wired correctly, but I'm not 100% sure. (Bipolar parallel, steppers has 8 wires).
The drivers are set to 3A, 48V. The steppers are rated 3A/phase.

Strange to me is, if I lower the amps to 0.7A I can run the steppers at approx 1000rpm..

Is this normal? Or do I have a problem somewhere? I thought more than 500rpm should be possible..

Thanks!

[hignog]

Have you got the details of the motor and stepper driver you are using?

[hub]

Have you got the details of the motor and stepper driver you are using?

Motor (Brand & model i don't know)
Bip. Parallel:
0.65Ohm
3,2mH
3,54Nm

Driver Leadshine ME742:
http://www.leadshine.com/UploadFile/...ves/ME742m.pdf

[hignog]

If the motor is an 8 wire motor the 3A maybe the current in series so you may need to set the curernt to 6A?
Also i hear that some manufactures have the name plate on an 8 wire motor as the unipolar current, so if this is right, it could be 4.2A in parallel.
I would check into the specifications of the motor further.

[hub]

Thank you for your help

The current is 2.12A in serial (bipolar) according to the motor data sheet.

[Dorsal]

??? How can you have a motor data sheet, and still not know the brand or model of the motor ???
Is this some kind of joke?

[hignog]

Ok, so the current in parallel is 4.2A.

Thank you for your help

The current is 2.12A in serial (bipolar) according to the motor data sheet.

[tivoidethuong]

may it is mid point resonance prolem

[hub]

??? How can you have a motor data sheet, and still not know the brand or model of the motor ???
Is this some kind of joke?

Sorry there is no brand or model on the data sheet... And the steppers don't have any labels either.

[hub]

Thanks, I found this information, I'll try putting some load and see if it's any better..

"Unloaded, the motor exhibits a fair amount of ringing. This ringing translates into motor vibration. The motor will often stall if it is unloaded or under-loaded, because the vibration is high enough to cause the motor to lose synchronism. Loading the motor properly will dampen these vibrations. The load should require somewhere between 30% to 70% of the torque that the motor can produce, and the ratio of load inertia to rotor inertia should be between 1:1 and 10:1. For shorter, quicker moves, the ratio should be closer to 1:1 to 3:1."

[James Newton]

The faster speed at lower current is a classic symptom of resonance problems. With the higher driver current, the motor is shaking more because it is starting and stopping faster with each step. That vibration reaches a resonance point and you can't move past it. With less power, the steppers vibrate less and so will spin faster... of course, they won't hold or pull in as much load.

If your driver will microstep, you will find it moves faster in microstepping modes than it will in full step... again, less vibration.

The other way to verify this, you have already found, is to load them down and see if that changes the top speed.

Mechanical vibration dampers, or a smoother microstepping driver are the real solution. If your motors were smaller, I would recommend our driver (the Linistepper) but 3Amps/phase is the outside edge of our envelope, and if you hadn't purchased a driver already, I would point you at Gekko, but since you have already paid for a driver (which one?), mechanical vibration dampers are probably the way to go. I believe I remember seeing a design made from a hockey puck that looked pretty good; you will have to search for it, I didn't keep the link.

Good Luck! And please let us know how it works out.

[hub]

Thank you very much James for your reply

Yes, my drivers (leadshine ME742) has microstepping, I tried many different values from 400 to 25000 ppr, but I didn't notice much difference regarding stalling. Yes a little bit, but not much.

I haven't got a chance yet to test with load because the rest of the machine is still under construction.

I'll let you know how it turns out.

[hub]

Just an update.. been doing some tests & research..

- Noticed the system (drivers) needs time after power up to settle, or to adjust or something..
- Motor heat seems to make stalling worse
- Tested on old version of Mach2, works a lot better reg. stalling.. I can run rapids up to 2500mm/min. Strange...
- I still haven't got a chance to test with load and/or resonance dampers..

:violin:

[James Newton]

I've been warning about motor heat for years, and how it decreases the strength of the motor. Chopper drivers end up causing the motors to heat. I've had all sorts of arguments from people denying that over the years, and there may be exceptions, but the average chopper driver pumping X amps into a motor will cause much more heat buildup in the motor than the average linear driver pumping the same amperage. The Linistepper keeps the motors cooler (it gets hot instead) and so they don't loose power to heat.

On the Mach2 version, how many steps per second are you sending? I wonder if you are reaching the frequency limit of the port? Perhaps the old version is more efficient and can generate a higher frequency?

[hub]

At least my tests seem to agree with you regarding heat. I'm not sure why, but guessing, maybe because of expanding, the distance between magnets and coils makes things worse..

Mach2/Mach3: I'm sending the same steps/sec. But in Mach3 I have the kernel speed set to 100kHz and in Mach2 to 45kHz I think (the max value selectable). Anyway, it's the same frequency. I'll try to set a lower 'kernel speed' in Mach3 and see if there is any differences.

[James Newton]

Heat is the vibration of molecules. Magnetism becomes noticeable when all the molecules are arranged in the same direction, each contributing, rather than canceling out, the individual tiny magnetic pull. Molecules can't be aligned when they are vibrating, so heat destroys magnetics.
[nomedia="http://www.youtube.com/watch?v=RWrTvB-oK94"]YouTube - Curie Effect Magnetic Heat Engine[/nomedia]

[hub]

Yes, that makes sense to me

[hub]

An update on this. I still haven't resolved the problem.
I have assembled the machine but there are still problems with stalling. I just run them slower for now.
I'm planning at some point:
- Heat sink/fan or something to cool the steppers
- Make some resonance dampers to see if they would help
- Tweak Mach and driver settings
- Try with more voltage than my current PSU at 48V

If all that fails, then I run the machine slow.
I will update to servos anyway at some point I hope.

[James Newton]

hub, nice to see you are still working on this. I wouldn't bother with trying to cool the motors... the heat is coming from inside where you can't effectively cool it because of the motor case. Resonance damping will help in the midrange, but not the top end. I still think the major problem here is the driver. Bipolar gives you more low speed torque, but a standard chopper bipolar driver will peter out pretty quick when it comes to high speed.

If you are game, I'm willing to make you a bet you can't loose: If you order a Linistepper driver, with tuning resistors to set it to run at 2 amps, and a CPU fan to keep it cool, and if you can dial your power supply down to our maximum of 35 volts, I'd be willing to pay you back just to see how they would compare to that bigger driver you are using now. If you buy it, build it, test it, and post your results with a picture showing the linistepper and your mill, I'll refund your purchase for the Linistepper, resistors, and fan. No matter if it works or doesn't, you will end up with no cost but your time. If you decide to take me up on it, post your order here: Linistepper,2Amp,FAN and add a note reminding me of this offer in the comment box.

Honestly, the Linistepper is probably underpowered for your motors and load, but I'm just really curious to see how much of a different a cool motor and a smooth unipolar (which has better high speed ability compared to bipolar) driver would make.

[hub]

Thanks James, yes I don't think it's mid range resonance really. Since stalling is only happening at the high end.

Sure, I'm game for your bet. And the price is very good if it works! You said no cost (refund) if I do the install & test and post report & pictures. No problem. I'll do that. But would that include delivery cost? I live in Finland.. It would probably almost double the cost of the parts.