Print surface leveling issues

[shurik 87]

OK, I give up - can't level my UM2 properly.

No matter what and how I try, it always comes out to this (two different prints, few days and few re-levelings apart):

No exceptions.

To make the things worse, I have to re-level after every print, even if I do not take the glass off. As you can see, there's a bigger gap on the right - well, it is always this way, regardless of my leveling efforts. There is always a bigger gap on the right.

Another thing is, during the leveling, the front of the printing plate can go up and down a tiny bit, since it sits freely in the air. This causes the paper always slip with little effort under the print head. When paper is removed, however, the glass can actually touch the head, leaving zero gap. This can be easily avoided by keeping an eye on the gap.

I'm starting to get desperate and suspicious - would anyone suggest how this can be fixed?

 

[IRobertI 521]

That's a weird one. Maybe check if all the rods are straight?

 

[industrialdesigner-uk 0]

I have had similar issues, but I think that I might have overcome the problem by doing the following:

Clean off any filament residue from the end of the nozzle.

When you start the levelling sequence, tighten up the finger screw at the back a few turns and do the same at the front of the bed. Do that before you start winding up the bed with the thumb wheel. This puts a bit more tension into the springs.

Make sure you adjust as carefully at the 1mm stage for all three points as you do for the paper 'fine' gapping. (I use a piece of card that is about 1mm thick.

In the final two thumb screw adjustments I think it's quite important to be really careful to match the left and right clearance....yes, I agree with you, it's really easy to get the bed to flex downwards when you push the paper in the gap, but a sensitive touch is the important thing.

I am new to the UM2 myself, but still, I hope I have been some help to you.

 

[mr.-waldorf 0]

Hi Shurik,

Put more tension into the bed springs and make sure that the springs are straight

Repeat several times the level wizard because when you adjust one screw some times changes the bed level and you need to fine tune the others.

Printing with 0.1mm inicial layer can be hard sometimes so as last resort you can try 0.2mm inicial layer

Be careful too much tension on the springs is also not good

 

[shurik 87]

Thanks guys.

Yes, I have to do re-leveling after every print, unfortunately, with the same results each time. It always comes out that the right side is too far away and if you look at the pictures, it seems like the surface is uneven - there are some "bubbles" closer and farther from the printhead.

Not quite sure what else can be done. :-(

 

[IRobertI 521]

Oh and make sure that nothing on the print head is touching the metal clips that holds the glass down. I think that was "fixed" in firmware by leveling a bit further back but I'm not sure.

 

[boraxflux 0]

We had somewhat the same issue, it happened after cleaning the glass plate, then we discovered we had the glass-plate upside-down --> warning sticker down on heaterbed), putting 'the right side up' strangely resolved the issue for us.

I put the glass plate upside down on our table, it wobbled a bit. (Or our table isn't super-flat).

It could have been a leveling issue. No conclusion yet...

 

[industrialdesigner-uk 0]

Looking at your photos again and I can see that there are thin patches of print material in areas other than one side or the other.

This got me wondering if you are getting a constant feed through the extruder(?). I had a faulty nozzle that kept running dry of material. I replaced the nozzle and now my prints are much thicker and have more consistancy.

Just a thought.

 

[shurik 87]

"nothing on the print head is touching the metal clips" - verified. We are good here.

Hmm, reversed the glass plate so the sticker "hot" faces down now. After yet another re-leveling the patchy patterns did change but they are uneven yet. It makes me more and more suspicious as to the quality of the glass plate itself. Maybe, I will open a ticket to replace it.

"This got me wondering if you are getting a constant feed through the extruder(?)." Well, we can't be 100% sure but the printer can definitely produce beautiful prints, especially if the bottom area is not too wide and is located near the center.

Let's give me the weekend to play a bit more. Your ideas are all welcome, of course.

 

[geeks 1]

I have a similar output to your printer.

 

When my nozzle heats longer sufficiently, it make a hole like on your photo.

 

I'm not sure but did you watch the temperture of the nozzle during operation?

 

[Anders Olsson 136]

What is your initial layer thickness?

I had no luck printing 0,1mm initial layer on my UM2.

Using (at least) 0,2mm initial layer makes leveling less critical.

When the first layer becomes transparent, the nozzle is too close to the build plate.

Running my UM2 that close at large surfaces will cause problems with the feeder.

The plastic can not escape the nozzle and the knurled gear starts slipping, grinding down the filament.

This makes the feed rate irregular on other parts of the print later on.

I have to be super careful when leveling the build plate to get good results.

A standard laser printer A4 paper should move with a very slight resistance between the nozzle and the bed for my UM2 to print well.

Every now and then I have to redo the leveling process since my UM2 seems to loose calibration with from time to time.

One step too high/low when fine tuning during calibration is enough to ruin print quality and reliability on my machine.

 

[shurik 87]

Thanks again for helping. Basically, nothing changed. I can't even count how many times I did leveling - no help.

The printer does produce beautiful prints, but the initial layers drive me nuts. See the latest one, 0.2mm thickness:

It's the same thing - far right corner is awful while others are acceptably good. Why? What could it be? Is it possible that the metal heated plate isn't even? :?:

I would open a ticket but the level of the service is worrying - they barely reply once in a while, ruining their own reputation... :(

 

[IRobertI 521]

Maybe you could try moving the bed up so it's very close to the nozzle, then move the head around while looking at the space between the glass and the nozzle tip. Any unevenness should be easy to spot that way.

 

[shurik 87]

OK, thanks for the tip, will do that. Meanwhile, the print on previous pictures got warped at, guess, right top angle. :angry:

Re-leveled, restarted. Same patchy pattern for the 1st layer - islands of thin, transparent flow and other areas of thicker, normal cover. Obviously, very think to the upper right.

When I look at the head, it can be clearly seen that it moves a bit farther and closer to the glass as it goes. A very tiny bit but enough to gen this unevenness.

Could it be that the glass itself is uneven and should be replaced? Or it's the rods that are curved? If this is the case, I'm even in deeper trouble. :(

What do you all think?

 

[IRobertI 521]

Remove the glass plate and then use a straight edge to check the glass perhaps? Lay the straight edge on top of the glass and then look if there are gaps between the glass and the straight edge. Maybe try doing it with the glass mounted as well to see if it gets bent somehow when it's mounted.

If the glass is flat then I guess the rods are the next suspect as you say. I haven't disassembled a UM2 yet so I can't give you exact steps for that. But it should be similar to the UM1, time consuming but not difficult.

 

[shurik 87]

Thanks IRobertI. Will check the glass. I'm not familiar with UM1. Besides, it takes some nerve to disassemble the brand new 2000Euro machine. I did that for the print head when had to remove a burnt out filament, but the rods... And then, what would I do with them? Even if they bend - it would be tenths or even less of millimeter. I can't handle this myself anyways.

However - have a look on these:

After the last re-leveling, the patches are very clear. What is it? Totally puzzled.... :(

 

[anon4321 16]

You could hold the rods together in parallel and hold up to a bright light to see if light shines through. Then roll one rod a partial revolution like 1/4 of a turn and recheck. then repeat for the other. Or if you had a mirror you could roll the rods on it and see if they wobble or always settle a certain way.

 

[anon4321 16]

Just had another thought. Instead of disassembling the machine, if you have some feeler gauges, you could use them to check the distance from the nozzle to the bed at various points where you are seeing changes in the layer. That would tell you if either the bed is not flat or the rods aren't straight or the bed isn't remaining level. I'm referring to these usually available at automotive stores:

http://www.bing.com/images/search?q=feeler+gauge&qpvt=feeler+gauge&FORM=IGRE

If there is a consistent gap between the nozzle and bed then I would suspect that the material feed and/or it's extrusion is inconsistent.

 

[illuminarti 18]

The regular pattern of thinner extrusion on the bottom makes me think that three things might be happening...

1) The two thin cross rods are slightly bent ( they just snap into the sliding blocks, so are fairly easy to remove to check

2) maybe the cross rods aren't properly seated at both ends. Looking along the length of the rods, they should be fully seated in the blocks with no gap between them and the black plastic part. Looking down on the printer, the sliding blocks should be parallel to the walls of the printer, and not angled in or out.

3) the bed may still not be leveled right - it's possible that the three screws are just about out of the threads leaving the bed floating too high. If any of the screws turn very easily, that's a sign that the screw may be too loose. I'd turn all three leveling screws several turns to the right to fully engage the threads and pull the bed down. You want all three springs to be compressed to a mid-range point, so that they have plenty of room to move in either direction when you adjust the height. And the length of the springs should be roughly the same in each case. Then repeat the leveling. I tend not to use a piece of paper... If you look along the surface of the bed you can easily see the nozzle and its reflection. The actual gap is half the apparent gap ... So initially level until the gap seems to be two mm, then on the second pass, adjust until the tip is just barely touching. Back it off until you see daylight. Let the bed settle, then advance it again until it's just touching. Let the springs settle each time.

[shurik 87]

 

First of all, many thanks to anon4321 and illuminarti for the suggestions.

Update:

This is how the bloody print finished:

 

The head stopped its left-right (Y?) movements, leading to a major head blockage along the way. That was quite upsetting, to put it gently.

 

It was a fixing bolt that went loose all the sudden, I was lucky enough to manage it into more or less accessible angle and tightened it. Then, had to disassemble the head (for the 2nd time already! :evil:) to clean it.

After all that saga, re-leveled and tried to print something. Seems very much better now. :!:

Question: The left-right upper thick rod on the back (you can see it on the last picture) has a clearance of about a millimeter between its black stopper and the wall, bounsing this distance as the pulley moves. The rest of the rods seem to be tight. Shall I tighten this one, too? It doesn't seem to affect quality and I'm not sure as to how to tighten it.

 

[illuminarti 18]

Yes, the black spacers should be tight against the walls to stop the movement, and keep everything in line. Push the rod as far as it will go the other way, so that the gap is as big as possible. Then loosen the pulley next to the gap, and push the pulley and spacer against the wall, then tighten the pulley again. Tighten it hard.

[illuminarti 18]

Left-right is the x-axis, btw.

[shurik 87]

OK, thightened the X axis. Seems to be much better now, but will need to do more tests for a definitive answer.