Axis Alignment Problem

[Nicolinux 288]

Hi,

I am running into a bit of trouble with the x and y alignment. I have mounted the extruder to the x/y frame. The first thing I noticed - the small wooden pads that should help tighten the sliding blocks have no effect:

http://www.flickr.com/photos/ultimaker/6244577512/

If I tighten the screw, the nut rotates with it and does not really push the claw down. However, my problem right now is that after aligning all axis and tightening the pulleys on the long belts, I can not move the extruder freely. It is not a fluid movement, but rather "pulsating". Here is a small video to demonstrate (turn up the volume):

The y-axis has the worst problems while x is way smoother.

While moving I see that the pulleys wobble on the 8mm rods and this corresponds to the movement problems. I loosened all pulleys and tried again, but the problem is still there, albeit not that pronounced. I guess it is related to belt tension and/or the sliding blocks.

The instructions are a bit unclear. If I want to have less tension - how would I do that? I can't open the claw on the sliding blocks too much because the belt would slip off. The rods are at a fixed distance and the pulleys are also fixed. I have no idea how to lessen the tension on the belts.

How do I fix this - or what else could be wrong?

Thanks,

Stefan

 

[illuminarti 18]

It doesn't look too too bad... the sound almost sounds like a grating metal-on-metal sound more than anything to me - but maybe that's just the audio quality. You can't really loosen the belts much but you probably don't want to... even if they were a bit tight now, they'll soon loosen up a bit with use.

When you try to move the head around, do it by pushing on both sliding blocks at the same time. That way you aren't torquing the head, nor bending the cross rods. If its hard to move with fingertip pressure, try loosening the end caps on the 8mm rods, and see if that helps them turn easier.

You can also add a few drops of light machine oil to help lubricate the rods. DONT USE THE GREEN GREASE - it's only for the Z screw.

When you're tightening the tensioner screws on the block, you need to insert something to stop the nut turning. A screwdriver blade might work, or the tips of a pair of needle nozed pliers.

 

[Nicolinux 288]

The problem is that I feel that something blocks a smooth movement and the pulleys wobble like crazy. I still can't figure out why that's the case. I loosened the end caps and this helped quite a lot but the uneven resistance when moving the head is still there. I have also tightened the tensioner screws with the help of anoter screwdriver blade - these should be somewhat tight.

In this video from the assembly instructions the head can be moved very very smooth and evenly. Sadly I am very far away from it:

 

Thanks,

Stefan

 

[nick-foley 5]

Your pulleys are not concentric.

This is major problem with Ultimakers. The pulleys they ship with are total crap. Read the (long) thread "Fixing Pulley Inaccuracy" and you'll see what some of your options are.

I switched one machine to GT2 pulleys and belts and the movement is much, much smoother. Not (just) because of the tooth profile, but because the pulleys are actually higher quality.

I also built one machine where I picked the 10 most concentric pulleys from all of the pulleys that came with 3 ultimakers. That machine also is very smooth.

 

[Nicolinux 288]

Yes the pulleys are bad. As soon as I tighten them, the axis movement is everything but smooth. When they are loose, the problem is not so pronounced.

Thanks for the info with the thread. I will read it. But I won't replace them anytime soon. I want to print already and I am sure that many other people with stock Ultimakers do get great results - even with bad pulleys. I bought an Ultimaker for a reason. Otherwise I could have stayed with the Prusa Mendel and fix stuff every other print...

 

[nick-foley 5]

Yeah, ultimately, the eccentric pulleys are a manageable problem. Don't worry too much about smooth head movement - you can get great prints without it. Check your belt tension more often, as that cyclic loading is going to speed up any problems related to movement there.

Mostly it just makes the machine (unnecessarily) feel like junk.

 

[gr5 2,167]

I have a little bit of the same eccentricity and go/slow/go movement and it prints just fine. I think your endcaps were a little tight but you should be good now - just keep assembling. Maybe put a drop of light oil on the x and y rods that go through the head.

 

[illuminarti 18]

Yeah, I have one particularly bad pulley, but the machine still prints just fine. Do the best you can to get the head moving freely, and then just start using it :-) There's a lot to learn and tweak before you get to the point where the pulleys are worth fixing. :-)

 

[Nicolinux 288]

Alright, thanks guys. I will go on and finish the assembly. I am too late for the second batch of great pulleys from a guy from Germany, but I placed an order anyway and if I get them, I will use them. If not I will ignore the problem the best I can

[Nicolinux 288]

Joergen hinted that my problem could also be related to the rods not being straight and square to each other. I did check the rods and most of them are not perfectly straight. But I think that's ok because most rods in printers are bent a bit and they still provide smooth movement. I also checked the perpendicularity between the rods protruding the print head and the x/y rods. That's ok too. But I didn't check if the oposing x/y rods are square to each other. I remember that I tightened the t-shaped screws for the frame a lot. Maybe the frame is deformed now and this affects the rods. I hope not. I am not keen on sourcing my own frame because I am sure it will break if I disassemble it.

[ciclopez 0]

I have exactly the same problem, I think that in my case the problem is that oposing x-y rods aren't square to each other. I thightened the main structure screws a lot too. I will measure it later when I arrive home and post the results.

 

[ciclopez 0]

I measured the distance between rods with a piece of cardboard with holes (like the pair of wooden pieces that come with the kit for axis alignment) and it seemed to be parallel to each other, so I tried loosening the end caps, oiling the 8mm ball and linear bearings, loosening the extrusion head bolts, moving it around and tightening them again and the movement was a bit smoother. Then I printed some pieces (to make a bit of "wear") and now seems to be almost as smooth as it should be. Maybe the next step is to replace the pulleys, as they seem to be not completely concentric.

I hope this helps to solve your problem.

 

[Nicolinux 288]

Thanks for the info. At least it is not the frame.

[aaron 2]

Also, keep in mind that no matter how you exert force onto the moving parts (either by the hot end unit or by the sliding blocks), you will not be feeling the friction caused only by the bearings on the hot end unit and the sliding blocks. You will either, depending on whether or not you have all of the pulleys tightened, be feeling the kinetic friction between the pulleys and the larger rails to which they are attached in addition to the friction of the bearings or you will be feeling the resistant force of the motor. Both scenarios will create an illusion of greater friction than is actually present.

Other than that, all I can say is what everyone else has said: be sure sliding blocks are aligned exactly, be sure belts are not too tight, be sure end caps are not exerting too much (or any) friction on the rods, and perhaps make sure your bearings pressed in the frame are strait?

I fiddled with this a bunch and found that the blocks can be tightened a bunch without over tightening the belt. I have all of my blocks clamped all the way and dont have any friction/overheating issues.

Hope this helps a little if any.

 

[Nicolinux 288]

Thanks for all the great tips. I re-assembled the x/y rods and pulleys, re-aligned the long belts, tightened the heck out of the pulleys and loosened the endcaps. Now the head movement is much smoother. Finally I am able to easily move the head with two fingers while holding the frame with the other hand. Loosening the endcaps had the biggest impact. They are very loose now I think the machine will shake them off after a few prints The only thing that remains are the uneven pulleys but I gues that's not a big problem right now.

 

[LePaul 321]

Has Ultimaker changed the pulleys? I just ordered my machine and am a little disappointed to see so much commentary on bad pulleys, people ordering replacements...so will/should I replace mine before trying to assemble?

 

[Nicolinux 288]

Sadly the didn't. Pulleys are still bad but don't worry about it just now. You will spend way more time worring about belt tension and asix alignment in order to get good print results. Apart from a nasty z-wobbling issue, I have already good print results and still use the stock pulleys.

http://umforum.ultimaker.com/index.php?/topic/2716-cannot-lower-bed-to-reach-endstop/

One more thing. The assembly instruction states that when you put the pulleys on the rods and add the belts, to make sure that the screw holes for the set screws on the pulley face inwards. Do follow this advice and try to align the set screw holes to be at the same angle when facing inwards. Since you will be tightening/loosening those pulleys a lot, it is a great help:

http://wiki.ultimaker.com/Ultimaker_rev.4_assembly:_X-Y_axes#Step_4:_Mounting_the_axes

 

[SandervG 1,521]

There have been some issues with the pulleys being off set but we always find a proper solution when we receive such a notification.

With the Ultimaker you receive the calibration tools to perfectly align your axis.

When you install the pulleys, you should replace the current black screws, with the silver ones that come in a package.

They have a better grip. Maybe after the first couple of hours printing you need to tighten them again, but then you should be set.

You should make sure the belts are parallel to your rods, and the short belts are tight.

This can be done by loosening the motor, push it down by hand and tighten it again.

The long belts also need to be tight, but not as tight as the short belts.

They can have some play.

If you find yourself in need during calibration, i would be happy to help!

 

[Nicolinux 288]

Well, here is my notification - my pulleys are really bad I can send you a video of their wobbling. But I have already ordered the better ones from forum user fhoensturm, so it doesn't matter (at least for me).

By the way, there is nowhere a note about the silver set screws. Maybe you could add it to the wiki (or I can do it since it is a wiki anyway).

 

[ginobrancazio 0]

Wow, I know this post is over a year old but I'm having the exact same problems. So I'm going to reassemble the x/y rods and pulleys and make sure everything is aligned properly. Hopefully that'll inprove things enough that I won't have to buy new pulleys. My linear bearings on the extrusion head also seemed jerky, though it only happened on one of the axes rods, should I replace the rod?

[macua85 52]

Mine is pretty much the same....probably attributed to the pulleys. However, I've been getting amazing prints straight away, so don't sweat it too much.