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coaster19

UM2 extruder motor skipping steps

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Hi all!

My school has owned an Ultimaker 2 for almost a year now, and thus far I've been able to fix any issues which have come along (I've owned a Solidoodle for almost 3 years now so I'm not new to hobbyist 3D printers). Recently, however, the UM2 has developed an issue which I am completely stumped by:

About 10 minutes after being turned on the extruder motor clicks and skips steps with or without filament. This happens regardless of whether the printer has been operated or idle (it does start earlier if trying to print something) and persists until the printer is turned off and on again. It fixes itself immediately after being turned back on and the material can be moved normally for another 10ish minutes. My first thought was that the motor/driver was overheating, so I lowered the current going to the motor, but the problem persisted. the electronics board appears to be fully connected. Any suggestions at all would be greatly appreciated!

Thanks in advance!

 

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I've uploaded a video of it clicking and turning back on without issue to YouTube:

I have since run the Extruder stepper without being attached to the back of the printer and the clicking still occurs. Should I try switching the E and Z motors? The software has the current set differently for the two by default, but they both look to be the same. I haven't tried messing with the Ultimaker firmware before, but if it's like Marlin then I'd like to try to switch their ports in the software (only switching connectors on the board rather than actual motors) to try to rule out a bad stepper driver.

 

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Really? I'm aware that the noise after turning it off and on again (24 seconds) is normal, but the "clicky-sounding" one at the beginning also rotates the motor less per turn of the dial on the front. This shows up in prints as severe under-extrusion, but only after a few layers have printed since the problem doesn't occur until the machine has been powered up for a few minutes.

 

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There's subtle differences in the clicky sounds. While printing the stepper can get noisier or quieter as the pressure is higher. When you are in "move filament" mode I believe it is doing large steps (not the minimum) so it is noisier then also. So I think these changes you are noticing have more to do with pressure than with turning the printer off/on or how hot it is. These steppers can handle very high temperature - they don't overheat easily. In fact some people turn their heated bed up to 110C and cover the top and front of the machine and print for hours with the steppers in that 40C environment (about 100F) and they are fine.

When you are printing and it clicks much louder - if you look at it it actually skips back 1/4 turn - and it underextrudes (stops extruding actually) for a second or so afterwards - that's a problem. That happens when the pressure builds up extremely high in the nozzle. Your from kansas so I will use pounds - about 10 pounds force on the filament at the feeder (enough if you try that you will lift the printer off the table) and over 100 psi in the nozzle (if there isn't friction elsewhere e.g. in the bowden or in the teflon isolator).

You may indeed have underextrusion issues but your video isn't showing this so I assume your printer is fine.

 

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You can see the top of the red filament in the video - it never reaches the second half of the bowden tube nor the extruder. I don't know where pressure would be building up in such a situation since the filament is very free to move within the tube. I was in move material mode both times so those sounds should have been the same (I would think at least!). Additionally, the motor never rotates backward - it just takes smaller steps. Note that even when it was "clicky" the red filament was still moving forward ever-so-slowly and was nowhere near the end of the tube.

Also, I don't know quite how the Ultimaker electronics are set up, but one of my first guesses was the stepper motor driver overheating - My Solidoodle used a NEMA14 for the x axis, so I know what an overheated motor feels like, and the Ultimaker's is definitely not :wacko:. I have heard that people have had issues with the motors skipping steps when the driver is overheating, so I thought that may be the source of the problem. I'd love to switch the drivers on the board if possible (like on RAMPS), but from my initial inspection of the connections on the bottom of the board it looked like they are integrated to the main board.

Oh and psi? pounds? This is part of the same system that has a barleycorn as a unit of measurement - 100% logical basis :-P (I don't care for imperial measurement despite living in 'murica)

Thank you for your help! I'm completely stumped by this issue and am happy to hear ANY ideas!

 

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I watched the video again. I must have had the sound off for the first 15 seconds or so because I didn't hear your voice the first time and didn't see the first part.

Yes - there appears to be something wrong. I think the steps/mm is off. I'll look up the "pololu" part specs but I suspect you need a new PCB. Fortunately for you, you reside in USA where you can get "local" support.

 

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Okay I looked at the schematic. The microstepping is controlled through hardware - not software. The 3 pins that set this are MS1,MS2,MS3. They are all supposed to be pulled high through a resistor R88 (circled in green below). A 4.7K resistor.

Something is wrong there - either MS3 has a bad contact (maybe it didn't get any solder paste) Or maybe R88 is missing on the board completely and the other pins just barely float high most of the time. Or U12 (the driver) is defective.

I recommend you go through support.ultimaker.com. Make sure you tell them you are in USA and you will probably get a new board shipped out today or first thing Monday. When you take out the old board inspect to see if R88 is missing! Or if something looks wrong with the MS3 pin (pin 11 on U12 as shown with blue arrow).

Um2 Bad Pcb

 

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Also when you post the support ticket include a link to this forum post!

Oh - what I failed to mention is that when all 3 pins are high (MS1,MS2,MS3) then you get 16 microsteps. But when MS3 is low you get 8 microsteps. That's what I think is happening. It's arbitrarily switching between modes.

 

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Since it's repeatable and happens after having been turned on for a bit, your first suspicion about overheating drivers doesn't sound too far fetched to me (and yes, they are integrated on the board). They shouldn't need any additional cooling under normal room temperatures unless there's something wrong with them. It would be interesting to see if it would make any difference if you unscrewed the board and pointed a fan at the thing and see if it removes the problem or shifts it time wise.

 

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I looked at my extruder during "move material" and in that mode it takes 14 "clicks" to move 1/4 turn or about 57 to go all the way around. Watching your video again I can see that it was working properly *after* power cycle.

This blows away my theory about the wrong number of microsteps because this controller doesn't do anything more than 16 microsteps yet you seem to be doing very little movement. Now I'm wondering if it's a firmware issue.

I had another report of very very bizarre firmware crashes in one of the newer firmwares. I recommend you go back to one of the "14" firmwares (from 2014):

http://software.ultimaker.com/old/

Try 14.09 - you have to install Cura 14.09 (Cura versions install side-by-side so you can have many installed at the same time) then use the USB to load the 14.09 firmware into your UM2, then use a newer Cura for slicing (or whatever one you want).

 

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Just to clarify - from some other things I've heard lately, the latest Marlin firmware can have crashes such that Marlin is over-writing memory and doing very bizarre things. It may be a few people have defective arduino or memory on the PCB but I'm very suspicious of the latest firmware (both 15.01 and 15.02). This other guy also tried 14.09 and it fixed his issues.

 

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