no bed adehsion/extrusion after a rebuild.  

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shua
 shua
(@shua)
New Member

Hi makers,

I'm looking for some support after recent problems.

I recently had three issues crop up at once so made the decision to take the printer offline and rebuild.

Problem number 1 was simple enough, failed top bearing on top x axis causing thick black streaks down top rod. Second issue was a crack in my MMU2s idler and the third was excess filament being dropped on prints from the hotend.

Upon dismantling the entire x axis and hotend parts I found a large mass of filament congealed around the top of the heatblock around the throat of the heat break. I'm presuming this is a leak due to lack of tightening or maybe too much pressure due to a blocked nozzle, so I removed the nozzle and replaced it and also removed the heat break and reseated it. I then moved to the MMU2S and replaced the idler body and completed the reassembly.

Since completing this work, running the wizard and starting to print some tests I've been completly unable to get the printer to A: adhere filament to the bed unless paperthin or B: extrude at all in some cases.

The initial print line across the front edge of the bed is absolutely fine, nice thickness and great adhesion but the actual printed line is either thin or broken or sometimes nothing at all. My first test was that pressed into the bed it took me 30 minutes of gently picking waferthin bits of filament out of the textured bed. I subsequently moved the z up and the filament just sticks around the nozzle.

Full Printer specs:

i3 Mk3S+ with MMU2S. Textured sheet. E3D Nozzle X 0.4mm printing in PETG.

Things I've tried:

Loosening the idler tension screws on the MMU2S (I believed feedrate could be due to restriction of filament travel)

Loosened Bondtech tension screw (same reason as above)

Checked filament alignment in both the MMU2S and the bondtech.

reduced temperature of the hotend.

Increased temperature of the hotend.

Increased bed temperature.

Cleaned the nozzle with a small brass brush to get any stuck filament off the nozzle.

Things I've yet to test:

Check E Steppermotor as it seems to be running fine.

Check heat break thermals as maybe I could be having heatcreep?

 

Any support would be super helpful!

 

Posted : 25/02/2021 1:54 pm
fuchsr
(@fuchsr)
Honorable Member

you said you moved live z up but this still smells like nozzle too low. 

Posted : 25/02/2021 3:45 pm
fuchsr
(@fuchsr)
Honorable Member

If you raise the z axis up a bit and extrude manually, is the filament coming out okay? If so, I think it’s definitely a live z issue. 

Posted : 25/02/2021 3:48 pm
shua
 shua
(@shua)
New Member

@fuchsr

So I attempted to adjust the Z by starting the calibration from zero and starting with a baseline with a clean bed and nozzle. from 0 all the way down to what I would think is ideal height it will hit the bed and curl up. Sometimes I get bed adhesion but it's intermittent. I raised z up and extruded about 10g of filament. Fresh spool of PETG from primaselect and a prusament fresh spool I get 98% consistency and then occasionally I'll get some bubbles in both. Prior to the dismantling I had really good bed adhesion with the "prusa part" grade of material finish.

Posted : 25/02/2021 3:57 pm
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