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Kirbs

UM2 Y axis losing steps

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So your Y axis is losing steps.  90% of the time that is caused by a loose pulley - there are 6 pulleys for the Y axis.  2 on the motor and 4 on the long belts.  Tighten them all although usually it's the one on the motor or the other one on the short belt just above the motor.  Those are hardest to get to but you can push the head around with your hand until the set screw is favorable/visible.

 

Tighten the hell out of those set screws.  I mean torque it so hard you think you might break the screwdriver.  If you use an L shaped allen wrench and you grip the short base of the L then your fingers should really hurt afterwards.

 

If you don't believe me you can remove the cover (2 screws) and mark the shaft and pulley with a sharpie) and then start another print and stop when it slips and check the marks.

 

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This worked for a bit then i got the same issue again, I pushed the servos down and tightens the belt attached to the servo, but thats it. What else can to do to prevent this problem, is there a youtube video or something?

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No.  don't push the steppers.  Tighten that tiny screw inside the pulley.  The belt is the black rubber thing - it goes around the aluminum pulleys.  The pulley's are attached to the stepper and the shafts with a set screw.  It is those set screws you need to tighten.  Not the belts.  Tighten them hard.  Very hard.

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18 hours ago, gr5 said:

No.  don't push the steppers.  Tighten that tiny screw inside the pulley.  The belt is the black rubber thing - it goes around the aluminum pulleys.  The pulley's are attached to the stepper and the shafts with a set screw.  It is those set screws you need to tighten.  Not the belts.  Tighten them hard.  Very hard.

I tightened each and every screw on the pully's, but i found that It would get really tight and i wasnt able to get my allen key out, until i pushed it even more and the screw went loose. Am i doing something wrong?

 

Many thanks

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Can you make a 5 second video?  This makes no sense to me.  Maybe you have the wrong size tool?  You want the same size hex tool as used for all the normal screws all over the machine. It's a 2mm hex tool.

 

Maybe you should start over and mark the shaft and pulley for the two pulleys on the short belt.  Then print something where you get layer shifting and then check to see which pulley is slipping on its shaft.  Then maybe remove that set screw and swap it with one of the set screws on a long belt.

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You've been concentrating on the Y stepper, right?  In the photos it looks like the part only moved in Y (towards the front of the machine).  That stepper is in the rear left corner.

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14 hours ago, gr5 said:

Can you make a 5 second video?  This makes no sense to me.  Maybe you have the wrong size tool?  You want the same size hex tool as used for all the normal screws all over the machine. It's a 2mm hex tool.

 

Maybe you should start over and mark the shaft and pulley for the two pulleys on the short belt.  Then print something where you get layer shifting and then check to see which pulley is slipping on its shaft.  Then maybe remove that set screw and swap it with one of the set screws on a long belt.

In the video, unless I'm spinning it the wrong way the screw just won't tighten. It does the fit several screws around the machine. It gets harder to push then it just pushes through.

Perhaps I'm doing something wrong?

What do you mean with the sharpie marking? Should I do it in the back left corners?  It is only the y axis that's shifting in all my prints, is it the left stepper that controls the y axis, or the right?

 

 

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I think I've finally done it. I was paying around with the head moving it around and when I hit home it just doesn't work. I can feel that it's trying because the head is easier to push, but it just doesn't quite have the strength. Is the stepper fried?

The printer only has 500 hours on it and I'm printing for bulk for a client right now, and this has put me back around a week. Is there any fix?

 

 

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In your first video it looks like you are rotating in the wrong direction? Thus loosening the screw instead of fastening it? Could you have a look at that? Normally the cork screw rule applies: turn right to fasten, left to loosen. And unless the video is mirrored, it appears you are turning left?

 

In hard to access areas, or when doing it from the back, or out of view, it may not always be obvious in which direction to turn. Then just take out your cork screw and hold it in the same position.

 

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12 minutes ago, geert_2 said:

In your first video it looks like you are rotating in the wrong direction? Thus loosening the screw instead of fastening it? Could you have a look at that? Normally the cork screw rule applies: turn right to fasten, left to loosen. And unless the video is mirrored, it appears you are turning left?

 

In hard to access areas, or when doing it from the back, or out of view, it may not always be obvious in which direction to turn. Then just take out your cork screw and hold it in the same position.

 

I'll be sure to take a look at that, but the stepper just isn't moving any more? Could that be attributed to the loose belts?

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3 hours ago, Kirbs said:

I'll be sure to take a look at that, but the stepper just isn't moving any more? Could that be attributed to the loose belts?

If the stepper motor axis is freely rotating in the pulley, I think yes. If the stepper motor isn't rotating at all anymore, I guess there is something else. But I have no experience adjusting belts and pulleys. So I would rather get a second opinion from specialists like gr5.

 

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yes you were loosening the pulley set screws instead of tightening.  The one on the motor and the one in the video are the two that you need to concentrate on.  And any other's that you may have loosened.

 

As geert_2 says, the stepper motor is probably spinning freely.  It's hard to see without removing the cover but I think that's a safe bet.

 

These printers are quite tough.  The steppers in particular are very tough.

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@gr5 I fixed the problem although I don't really know what was wrong. The stepper want moving at all then I tightened the belts and it works now. Despite tightening all the belts, it's still slipping. And I really have no idea why. I can't push the stepper belt together and can't tighten the other belts any more. The image is supposed to be a dis circle

15220980090366361872988152763333.jpg

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@gr5 while printing, i can easily push the head around in the y direction, but not the x.

The belt stays perfectly attached to my stepper and the stepper let's me push it around anyways. It didn't seem to have the same strength to resist against my like the x axis does.

Am I doing something wrong with the belts still it of the stepper getting sloppy?

 

You can't see it in the video but when I hold the head still there is no slipping on the stepper. It just isn't strong enough to push it

 

 

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Don't say you "tightened the belts".  They shouldn't need tightening.  It's the pulleys that need tightening.

 

You asked about the marking of pulleys.  I meant use a sharpie/permanent marker.  Mark the pulley and then mark the rod at the same spot so the marks/dots line up.  That way you can see if the pulley slipped and which one slipped.  To do this with the motor you need to remove the left rear cover.  I think it's time you did that as it takes all of 2 minutes.  You probably need to shove the bed all the way down first.  There's only 2 screws holding that cover on.  Remove the screws and the cover should come off (it has tabs pushed into slots but if you wiggle it a bit it should come out).  Now you can remove the stepper and mark it and tighten the hell out of that screw on the motor pulley.

 

Personally I wouldn't bother with all that but it feels like progress has been slow so far.  I'd just use a long hex driver and get it in there at the awkward angle and tighten the hell out of that set screw on the motor.

 

Did you tighten the pulley on the Y stepper?  That's the one hardest to get to and also the most likely one that's a problem.  Tighten it so much your fingers hurt.  Very tight.

 

Try pushing the head around.  Is it about equal force to move it X versus Y?  it should be about equal.  Very approximate.

 

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On 3/27/2018 at 12:10 AM, gr5 said:

Don't say you "tightened the belts".  They shouldn't need tightening.  It's the pulleys that need tightening.

 

You asked about the marking of pulleys.  I meant use a sharpie/permanent marker.  Mark the pulley and then mark the rod at the same spot so the marks/dots line up.  That way you can see if the pulley slipped and which one slipped.  To do this with the motor you need to remove the left rear cover.  I think it's time you did that as it takes all of 2 minutes.  You probably need to shove the bed all the way down first.  There's only 2 screws holding that cover on.  Remove the screws and the cover should come off (it has tabs pushed into slots but if you wiggle it a bit it should come out).  Now you can remove the stepper and mark it and tighten the hell out of that screw on the motor pulley.

 

Personally I wouldn't bother with all that but it feels like progress has been slow so far.  I'd just use a long hex driver and get it in there at the awkward angle and tighten the hell out of that set screw on the motor.

 

Did you tighten the pulley on the Y stepper?  That's the one hardest to get to and also the most likely one that's a problem.  Tighten it so much your fingers hurt.  Very tight.

 

Try pushing the head around.  Is it about equal force to move it X versus Y?  it should be about equal.  Very approximate.

 

Gr5, thank you very much for being patient with me, turns out my 1.5 mm hex key was really warped, preventing me from tightening the pulleys. After getting a new one and tightening the y axis stepper pulley it works just fine.

 

Many thanks

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On 3/28/2018 at 5:31 PM, gr5 said:

You should be using a 2mm hex key but sounds good.  If it works, it works.

 

@gr5, sorry it was a 2mm key, but I'm back to having the same problem now after one successful 40 hour print. I'm getting heavy y axis shifting, but this time all my pulleys are super tight, my fingers are hurting and yet it still shifts. I did as you suggested and put sharpie on all pulleys, expect the actual stepper because I don't know if I can mark that one. But I'm seeing absolutely to movent on any other pulleys.

 

I really don't know what's going on but if it continues it's gonna cost me some clients.

 

Many thanks gr5!

Edited by Kirbs
Typo

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Maybe you tightened the pulleys without pushing them against the sides and therefore the rods are moving during printing? 

 

A simple way to check is where the rods protrude from the outside, is to hold your fingers on them while printing and feel if they move in or out the should be quit level to the holes in the covers.

 

Don't be offended, but turning a screw loose while you think you're tightening it, it might be best to take it to the shop or have someone take a look at it which knows what they are doing, especially when you need it for a client who is waiting for the parts.

 

Hope it gets fixed soon.

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2 minutes ago, phantom said:

Maybe you tightened the pulleys without pushing them against the sides and therefore the rods are moving during printing? 

 

I have to be pushing the pulleys while tightening them? Could you elaborate on they a little more?

 

Yeah I've been considering taking it into a local shop if I can't fix it by the end of the week. The only problem is there is one shop in my province and it's far away so I've been putting it off.

 

Any elaboration on how to tighten the pulleys would be appreciated @phantom. I'm sure I'm tightening them the right way but I could just be doing process wrong.

 

Many thanks

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Loosen the pulleys, push the rods in from the back or the side, depending on which axis your working on,push the pulley to the the side it is sitting at with your other hand while tighten the screw. 

Push as per the arrow in the picture:

 

Screenshot_20180331-171020.jpg

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