UMO makes bad movements and loud noise

[marian 0]

Hi,

Here is a video of my problem:

 

- the UMO works fine for a few minutes

- then it goes to crazy mode. It makes a loud grinding noise and moves away from the part

- I have made successful prints before

- The head can be moved around easily

- The pulley screws are tight

- I added sewing machine oil to the axes, now they move even smoother but the problem persists.

- Only the X axis has a problem.

What's the problem with my printer and how can I fix it?

Thanks in advance!

[Torgeir 242]

Hi Marian,

This sounds like a too loose pulley belt. The stepper pulley can rotate, while the belt slip step by step, due a low belt tension. This is what I’ll think make the noise.

Check the tension of the x-stepper short belt.

Just loose the four screws that’s hold the stepper, then tighten the belt by pressing the stepper down, then re tight the four screws while holding the stepper down.

Tight it so it’s has the same tension as the good one, touch the belts like a “guitar string” and make the slack belt sounds like the other (good) belt.

Hope this is the problem; then it should be easy to fix.

Good luck.

Torgeir.

[Torgeir 242]

Hi Marian,

Just unscrew those four screw so they are a little loose, dont remove them.

Then you can slide the r/h inner (X) stepper a little up and down, down tighten the belt.

[marian 0]

This didn't solve it unfortunately. The pulley belt on the X axis is now tighter than the one on the working axis. I made another print today and it failed like the video shows, though it worked for 30mins.

[Torgeir 242]

Hi,

Sorry to hear this. The next step is to see if the x-stepper motor actually move or if it just misses a step, as it is trying to move but just step back again. There might be a loose connection or a faulty driver for the x-stepper motor. A faulty driver or a loose connection can reduce the amount of current to the stepper and make it very "weak".

As a test we often do some trick in order to isolate/locate the problem. In this case we would swap the x and y connector of the two stepper motors to see if the error swap to the other side or if it stay at the same side.

Cause I do not know the UMO in detail, as if the motors will go toward the end stop, or not, when the x-stepper and y-stepper connector are swapped. So I can’t recommend this approach.

However, there might be someone here with this knowledge.

Anyway, good luck.

[marian 0]

Hi,

I just swapped the motor connectors and now the Y axis is broken while the X axis works.

This confirms that the problem is somewhere on the PCB and not a mechanical issue.

Pulling the driver out and putting it back in solved the problem, but after a minute of printing it was broken again.

Should I buy a new driver? Or should I solder the current one to the board?

[Torgeir 242]

Hi,

You've made good progress here.

As your printer suddenly become like this, I would check the soldering of the connectors (or soldered feed through pins) with a good magnifier glass (X5). Look at the soldering around connector pins on the "stepper driver PCB" and on the other side mating connector.

If you're lucky it might just be a pin that become loose or just not soldered at all.

Ok. Good luck.

Torgeir.

[marian 0]

I tried to look at the broken driver PCB but I didn't see anything unusual.

I also bought an A4988 stepper driver and put it on the printer. It doesn't make the motor move at all (no stuttering either). Is there anything I need to do with the new driver? Can I use an A4988 at all?

[Torgeir 242]

I tried to look at the broken driver PCB but I didn't see anything unusual.

I also bought an A4988 stepper driver and put it on the printer. It doesn't make the motor move at all (no stuttering either). Is there anything I need to do with the new driver? Can I use an A4988 at all?

 

Hi,

Did you actually swap the two drivers?  An important question for fault finding here.

You said you pulled it out, then installed it again...

As you have an UMO, I'll think the one (driver) used there is A4983. I know the UMO can be upgraded to use same driver as UM2 and maybe is delivered with (A4988) on later model.

You can check the P/N on top of the (Integrated Circuit) IC mounted on the driver PCB.

I'll think there is some pin issue between those board, but I'm sure anyone in here have the answer about this matter.

Good Luck.

Torgeir.

Edited June 1, 2016 by Guest

[marian 0]

I can tell the drivers apart, since I have 3 working ones, one broken one (grinding noise) and two new ones (no noise or movement at all).

In this post, it seems like the A4988 drivers are shipped with the UMO.

Accodring to this page, the 83 and 88 are compatible, except the 88 has overheat protection.

[Torgeir 242]

Hi,

Great info in here, yes I understand the problem here, -I'll think...

The A4988 differ from the A4983 that's have no current control.

In the UM2 the current is controlled by firmware (the controllers "op" system).

For the UMO you have to set the current limiting (current increase, will increase the temperature).

As the driver PCB is set to a low level (current) state, this might be the reason your stepper motor do not move, -you need to adjust the current setting yourself.

Go to this page:

https://www.pololu.com/product/1182

Go all the way down to the current setting. Here you'll find all the information of how to adjust your driver PCB. Sure you'll need a multimeter in order to adjust this Vref voltage.

(I did not find the Vref marked on the PCB, but it should be at the potentiometer (metallic plate) where you do the adjustment.)

Based on your stepper motor type, you'll need to calculate the Vref setting.

Clockwise decrease the current and counter clockwise increase current.

Check out the video of what to do.

Yes, this turn out to be a little more than that, but this is not as complicated as seems. Just takes a little more time.

Well, good luck.

Thanks.

Torgeir

Edit: I'm still wondering about the faulty PCB that's start working for a minute...

Edited June 2, 2016 by Guest

[gr5 2,173]

The driver is getting too hot after a while. Is it getting good airflow? If so then you want to adjust the current a little (probably reduce it).

Be aware that moving those potentiometers as described above just the tiniest bit can blow them up. But I'm not sure what else you can do. Basically turn it about a half millimeter to a lower current value as described in the photo that shows which way to turn all the different pololu's to get lower current.

[marian 0]

I just checked the driver PCBs. The old and new ones all have Vref = 0.7V. Which voltage or motor current should I use?

About the airflow: The fan is very loud, maybe it doesn't run smoothly.

Edited June 9, 2016 by Guest

[tommyph1208 55]

I just checked the driver PCBs. The old and new ones all have Vref = 0.7V. Which voltage or motor current should I use?

About the airflow: The fan is very loud, maybe it doesn't run smoothly.

 

The PCB fan on the UMO is notorious for wearing out its bearing and start making alot of noise and possible move less air. I think a lot of people (incl. me) replace them with PC cooling fans mounted to a custom printed cover (you can find lots on eg. Thingiverse or youmagine).

However, since your printer is faulty, you cant really print one at the moment... You would have to get creative with some other means of cooling while printing a new cover (stack the printer on something and put some fans underneath, put it outside, something?) if the print is a success, it will confirm cooling to be your problem (though it is weird it only happens with one driver).

Did you check the passive heat sink on the faulty driver?

Also: Be careful when taking drivers in and out of your machine, putting them in the wrong ways (turned 180 degrees) will blow them up...

[marian 0]

Unfortunately I physically destroyed the original driver that wasn't working. So I need to find a way to get the A4988 drivers to work or buy other ones.

The cooling should be enough since the other 3 motor drivers work. Altough I'll replace the fan once all the motors work again.

[tommyph1208 55]

Unfortunately I physically destroyed the original driver that wasn't working. So I need to find a way to get the A4988 drivers to work or buy other ones.

The cooling should be enough since the other 3 motor drivers work. Altough I'll replace the fan once all the motors work again.

 

Alright... The A4988 drivers you got should be a direct plug in replacement (provided that you turn it the right way), and the 0.7V Vref sounds like a very good starting value, so if you can't get those to work your problem must be one step further down, ie. the driver socket or the UM board itself.

Try one of your new drivers on one of the motor channels that work currently, to eliminate any doubt if the drivers are working or not...

Edited June 10, 2016 by Guest

[marian 0]

I'M PRINTING AGAIN!

Turns out, out of the two replacement driver boards I bought, only one was working.

Thank you so much to everyone who helped!

Edited June 10, 2016 by Guest