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Dim3nsioneer

Broken stepper driver

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This morning, after having set up the x-y-rods in a way they produce less friction, I tried to reduce the motor current of both axis. I thought reducing the current is no risk for the stepper drivers - I was so wrong!

Although I immediately switched off the printer when it skipped, I seem to have managed to damage the y axis stepper driver seriously. The motor just skipped and even when the printer was switched off and disconnected from USB, turning the y axis felt very 'rough'.

So the next step was, disconnecting the y motor from the UM shield and - it could be turned again smoothly. I also checked the two phases of the motor - they are still fine.

After having adjusted all the drivers to reasonable level, I took the stepper driver from my second extruder and put it into the x axis. Everything works fine again (except the second extruder which has no stepper driver anymore... :sad: ).

Why do I write all this? First, to prevent anyone else from doing the same mistake.

Second because I would like to know if anybody could give me a hint, what exactly happened. I guess the stepper driver is history now and I have to buy a new one. However, I do not see any obvious damage on the print.

 

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I've had a similar skipping motor once, also because of a broken stepper driver.

Cause was that the stepper driver became to hot, the PCB fan just stopped during a print so there was no cooling anymore.

Did you turn the stepper driver the right way as explained in the picture blow:

UM Stepper

 

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Yes, I did. I have the blue ones. Actually I turned the x and the y axis driver simultanously (of course without power!) And nothing happened to the x axis driver although this motor was skipping as well. Maybe just luck?

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It seems to.

If you set the X stepperdriver back to its original state, is it still skipping?

It seems that the motor is not getting enough power from the stepper.

I also tuned my stepperdrivers, twisted the screw 1/20th of the axis each time, very carefully.........

 

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Even a bit higher current doesn't help. And as I mentioned already, you can feel the difference by manually turning the axis with the stepper in place. If I put a different stepper into that socket, the same motor runs smoothly. So I think it must be a short cut somewhere in the stepper driver and the induced voltage from turning the motor axis is enough to produce this strange behaviour.

 

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Are you going to get them from Ultimaker? Lots of people sell these. I assume they are compatable but I don't know - I guess I'd have to look at the pin out diagram. Try googleing "reprap pololu"

http://www.banggood.com/3D-Printer-A4988-Reprap-Stepping-Stepper-Step-Motor-Driver-Module-p-88765.html?currency=USD&utm_source=google&utm_medium=shopping&utm_content=miko_ruby&utm_campaign=all-us&gclid=CKO39rP4pL0CFchQ7AodlQoAtA

 

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Make 5, then it's a whole new set also for the extruder drive :smile:

 

Let me put it this way: priority on further brave tests with stepper drivers has significantly decreased since yesterday... :shock:

 

Are you going to get them from Ultimaker? Lots of people sell these. I assume they are compatable but I don't know - I guess I'd have to look at the pin out diagram. Try googleing "reprap pololu"

http://www.banggood.com/3D-Printer-A4988-Reprap-Stepping-Stepper-Step-Motor-Driver-Module-p-88765.html?currency=USD&utm_source=google&utm_medium=shopping&utm_content=miko_ruby&utm_campaign=all-us&gclid=CKO39rP4pL0CFchQ7AodlQoAtA

 

Thanks for the link. For now, I think I stay with the little bit more expensive UM drivers as I need them a.s.a.p. But the thought of compatible drivers crossed my mind when I read about Nick Foley's tests with Pololu DRV8825 . If I buy some other stepper drivers in addition, I still have the UM stepper drivers as a fall-back solution.

 

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For now, I think I stay with the little bit more expensive UM drivers as I need them a.s.a.p.

 

Hi. have you tried the replacement drivers from Ultimaker yet? I have had almost exactly the same problem with one of my drivers as you describe in your original post. The original drivers from Ultimaker that I have use the A4983 chip and I've tried several replacement drivers that use the newer A4988 chip with no success.

I haven't had time to do any really in depth investigating but it seems like the new A4988 is shutting down due to one if it's new saftey constraints [that the A4983 does not have]. If this is a correct assertion then this points to the original A4983 being erranously used outside of specification.

The A4983 is no longer made so I presume the Ultimaker drivers now use the A4988. I'd be interested to know if you've had any luck with the new Ultimaker drivers before I spend €16 on delivery.

 

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Hi. have you tried the replacement drivers from Ultimaker yet? I have had almost exactly the same problem with one of my drivers as you describe in your original post. The original drivers from Ultimaker that I have use the A4983 chip and I've tried several replacement drivers that use the newer A4988 chip with no success.

I haven't had time to do any really in depth investigating but it seems like the new A4988 is shutting down due to one if it's new saftey constraints [that the A4983 does not have]. If this is a correct assertion then this points to the original A4983 being erranously used outside of specification.

The A4983 is no longer made so I presume the Ultimaker drivers now use the A4988. I'd be interested to know if you've had any luck with the new Ultimaker drivers before I spend €16 on delivery.

 

To be honest, I ordered the Pololu DRV8825. I managed to get one of the old steppers working again by increasing the current a tiny bit. So I'm not in the hurry I thought I would be. But I let you know anyway hot it turns out.

I'm not sure which drivers (A4983 or A4988) were actually in my UM1. I'll have a look.

 

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To be honest, I ordered the Pololu DRV8825. I managed to get one of the old steppers working again by increasing the current a tiny bit. So I'm not in the hurry I thought I would be. But I let you know anyway hot it turns out.

I'm not sure which drivers (A4983 or A4988) were actually in my UM1. I'll have a look.

 

Have you tried using the DRV8825 or are you just using the old driver still? My broken driver is irreparable so I'm just trying to find any driver that will work as the originals are no longer available. Thanks.

 

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Have you tried using the DRV8825 or are you just using the old driver still? My broken driver is irreparable so I'm just trying to find any driver that will work as the originals are no longer available. Thanks.

 

I think my old drivers are A4988. They are mounted on a blue pcb. I still use them. Well, 4 out of 5... :sad:

The DRV8825 are somewhere above the arctic ice at the moment I think... ;)

 

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I've had a similar skipping motor once, also because of a broken stepper driver.

Cause was that the stepper driver became to hot, the PCB fan just stopped during a print so there was no cooling anymore.

Did you turn the stepper driver the right way as explained in the picture blow:

I have to make a confession. Yes. I did it. I turned them in the wrong direction. I must have been in a kind of mental absence a week ago. :wacko: :twisted:

BUT: It seems that the x/y stepper driver of my UM1 kit were not set to a resonable amount on delivery. This morning I found out that I printed with 2/3 settings instead of 1/3 setting for half a year. Better late than never... :roll:

The good thing is, my UM1 is now significantly less noisy and the stepper do not become 60°C hot anymore. :)

Question to all you stepper adjusters out there: How are you adjusting the current? By measuring Vref on the stepper driver (with extra cooling by some fan or similar, otherwise the stepper drivers will overheat) or are you just bravely turning the screw until it seems fine?

It would also be nice to know how they do it at UM.

 

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I've ordered a DRV8825 some hopefully I will have some success with that.

I have tried several A4988 from different manufacturers, set them using Vref before applying load and none of them have worked. Perhaps I have some differently spec'd motors as I have a pretty early model (back when all the steel bars were the same thickness rather than the crossing bars being thinner).

 

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So I recently had to replace a bunch of drivers (don't ask, I'm stupid).

The goal is to have enough current so you don't miss steps.

So I put the drivers in (with the power off, obviously) and very gently turned the screw to the limit in the counterclockwise direction. Then I power on and use the ulticontroller to drive the axis around. When the axis is moving, I try to stop if with my hand. Fully counterclockwise, it stops easily. So I powered off, turned like a 1/4 and powered on and repeat. It still seemed to skip with very little pressure. So power off, tweak like 1/20 and repeat. I did this until I felt there was enough force before skipping. Using this method, you are feeling the force that makes it to the head. At that point, you don't need a lot of force to move the head around.

Using this method adjusts the current for the the drag/friction of the belts in each axis.

I tuned them a little more than the force I felt was required so that high step rates don't skip.

For the extruder, I just tried to stop the big gear while it rotated. I actually need to turn that one down, the stepper has been running pretty hot.

For the Z axis I don't think much force is required. Just test by trying to hold the coupler.

It's obviously subjective. Try to find the sweet spot of just enough current to prevent missing steps at high speed and changes in direction.

By the way, I measured the vref of the driver that came with the UM1. It was .67 which I believe works out to 1.675 amps.

 

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It's probably the acceleration you need to test out. I would think that the most likely time to lose steps is when acceleration is high. Of course to get high and sustained acceleration it's simplest to do long fast moves.

You will love your printer better if you increase your Z acceleration. I doubled it which drastically speeds up layer changes and makes the Z seam much smaller. But if you are plaing with current you might be able to triple or much more increase it. I think Simon (Illulminarti) increased by something like 10X the default Z acceleration. I tried his recommendation (don't remember exactly what it was) and got many skipped steps and settled on double the default.

 

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