Second print head too low even after manual bed leveling

[waveletlet 0]

I'm having a problem with my second print head not being z-aligned correctly. It seems to be so close to the bed that the first layer (or two?) doesn't really come out. If I do a print with only that head, it can successfully finish and looks normal except the brim is the faintest shadow on the build plate. If I do a print with both heads, eventually it'll do the sweep the plate dance.

 

Pictures attached from print with both heads. Identical model being printed with two different brands of black filament (trying to compare brands), the one on top is the first head and the one on the bottom is the second. Brim is being printed with head 2, support with head 1. In the first two pictures you can see the "ghost" brim from head 2. Images 3 and 4 show difference in extrusion between models that should be at the same printing status/height. And 4 and 5 show the print from the 2nd head detaching and sweeping around. First the head knocks the 2nd model;s support off, and I think that's what screws the rest of the print.

 

These pictures were done after:

- cleaning the print head (cold pull) to make sure there was no jam and the filament is feeding correctly

- removing the print heads, and comparing them for any obvious differences in height

- manually leveling the build plate

 

I'm on firmware v5.2.11.20190503.

 

Oh and the priming blobs look about the same size and etc.

 

Edited November 3, 2019 by waveletlet
extra detail

[waveletlet 0]

Silly me, I never measured my test objects. When I said prints with the head could successfully finish and look normal, I was actually wrong! Theyr'e about 2 mm short.

This all started happening after I updated my firmware from something over a year old to v5.2.11.20190503. Unfortunately I didn't take note of what the previous firmware version was. After the firmware update I did an XY calibration and the 2nd extruder came out all ghostly as above but I thought it was a filament (wet, old...) issue and ignored it.

 

[gr5 2,234]

The answer depends what printer you have.  UM3/S3/S5.  If you have a UM3 then I recommend you disable automatic leveling and do a careful manual level.

 

However I suspect this is an S5.  Something is going wrong with the autoleveling I think.  The second head is too close or too high off the glass (you can verify by pushing up or down on the glass while it prints with the second head and filament should stick nicely).

 

Autolevel failures are usually caused by spring issues.  You basically need the spring in the cores to be stronger than the spring in the bed.  This is a simplification but often one needs to make the core springs stronger or the bed springs weaker.

 

You can weaken the bed springs by moving the bed up a bit so the 3 springs are compressed less.  Try 10 rotations of each of the 3 levelling knobs, then redo manual level.  You can test the cores by putting the nozzle on a postage scale and pushing down until you first start to see a tiny bit of movement.  This should happen at 1.0 kg (or higher).  Less than 1kg force needed means the core may have vertical calibration issues.

 

Which model printer do you have?

[gr5 2,234]

By the way, errors in Z screw, Z stepping would affect both left and right nozzles equally because they are both controlled by the same Z movement hardware.  So parts will be the same scale height (with a possible tiny offset < 0.3mm).  Any offset > 0.3mm will not allow the print to print the bottom layer at all (either too close and bottom layer is transparent or too high and the filament won't stick to the glass at all - get dragged around).

[waveletlet 0]

It's a UM3E. The first print head prints fine so I don't think it's the Z screw. I did do a manual level (more than once!) and still have the problem, but I'll try with the loosening the bed springs suggestion.

 

 

 

 

[waveletlet 0]

Ok, 10 rotations of the back leveling knob (from finger tight) makes it so loose I can't finish the leveling. I can't get the front corners high enough to match, and also can't get it close enough to do the calibration card fine tuning. Even 8 full rotations is too loose. Does that say anything about the state of the bed springs?

 

I had the machine in storage for about a year, maybe there's some oiling/cleaning needed?

 

But again, the first head prints 100% fine, measured a calibration print with calipers and everything.

 

I'll try swapping the heads and see if that changes anything. If the spring in the second head is bad, replacing it with the first head should fix the problem, right?

 

EDIT swapping the heads didn't  help either.

Edited November 4, 2019 by waveletlet

[gr5 2,234]

Call them "cores" please, not heads.  🙂

 

When the "bad" core is printing try pushing up or down on the glass bed to make sure we understand the issue.  I'm expecting the right core is too high off the glass and so it doesn't stick unless you push up on the glass?

 

Also if you grab the lever on the right side of the head and slide it towards you and away from you repeatedly does the right side core go up and down?

 

Maybe I don't understand the problem in the first place so more photos/video might help me understand better.

[waveletlet 0]

Just the opposit, the right core is too low and for the first few layers is smushed so hard up against the glass no filament comes out. I did a calibration print with five 1 mm steps, and it only prints 3.5 steps. The first approx 1.5 mm are completely lost, but you can see the ghost of the missing steps on the printer (where it was pushing down so hard nothing was coming out). So basically, the first 1.5 mm of anything I print on that side are lost. And while it's trying to print that 1.5 mm, it's pushing flush against the glass , which I'm assuming isn't great for the print core or the glass.

The raise/lower switch does work.

With the manual bed leveling, if I do it very loose (8-10 rotations clockwise on the back screw), there isn't enough tightness in the springs to get all the corners to the same height. And when I do the fine calibration with the card, the bed is already at the top and so I can;t get it any closer. With 5 rotations, I can get everything level, but I'm having the issue of the right core thinking it's higher up than it is.

Autoleveling can complete successfully.

I'll post more pictures whenever my current print job finishes.

[gr5 2,234]

Okay so it sounds like you found a good setting for the 3 screws.

 

It's unclear to me if you turned off autoleveling.  Autoleveling doesn't help much on the UM3E like it does on the S5.  On the S5 it is multipoint leveling (around 30 points) and your glass can have many bumps and those are all compensated for.  On the UM3E it only affects height and tilt.  Which you can adjust more accurately with manual leveling.  I find one manual adjust lasts for over a year whereas autolevel can occasionally mess up.

 

Maybe show a quick video of your manual level procedure where you show just the adjustment at the rear for both nozzles using calibration card (and just skip through the front corners as your problem isn't so much leveling as height calibration).

 

Did you mess with (upgrade) your firmware recently?  There's a very small chance that doing a factory reset will fix your issue but I would avoid that as then you have to calibrate things like the lift switch and all your XY calibrations have to be done over again and so on.