Prusament Pearl Mouse frustrations  

Prusament Pearl Mouse frustrations

I am having a horrible time printing with Prusament Pearl Mouse and figured it was time to turn to the wisdom of the forums.  This is going to be a pretty detailed post.  Please read it before you comment or give suggestions.  While I realize one should always be polite and gracious when asking people for help, if you suggest something that I explicitly spelled out as having tried, I will politely and graciously make fun of you.  🙂

Quick summary:  I'm trying to print some high detail parts in Prusament Pearl Mouse and can't get through an entire print without the extruder skipping -- I'll go into more detail in a bit.

Background:  I have a Mk3, built from a kit.  Recently overhauled with new X/Y rods and bearings.  Hotend was stripped down and checked out.  The Prusa heat break was replaced with a stock E3D heat break.  First layer calibration done (bed level to under +/-0.05mm).  Extrusion multiplier calibration done.  Linear extrusion calibration done.  Firmware is 3.8.1-2859 (official release).  X and Y dimensional tolerance is spot one.  On a 40mm cube, one side was 40.04mm and the other 40.00mm. Slicing is being done with PrusaSlicer-2.2.0.  As noted, the problem filament is Prusament Pearl Mouse -- brand new spool, fresh out of the bag. 

For reference, here is a close up of a first layer calibration square, the bottom of a 40mm extrusion calibration square, and the side of same square.

This is the piece I am printing.  This is an earlier, test print, done in Hatchbox Silver PLA with a 0.4mm nozzle and 0.15mm layer height.  This is a very old spool of PLA that lives on the printer and is used for random prints.  So while there is some variation in extrusion visible, I think most would agree this is a pretty high quality print for PLA filament that's been sitting out for probably six months.  This print had no issues at all with the extruder skipping.

Now, to the current problem. 

I started on printing the above piece with a 0.25mm nozzle and 0.1mm layer height -- about six and a half hours to print.  I used the included 0.25mm nozzle profile and Prusament PLA profiles.  I also did and extrusion width check with the nozzle before and found it to be spot on. The extruder skipped here and there, on occasion, but the print did finish without too much noticeable impact on printing, but some definite areas of under extrusion.

An attempt to print three at one time failed completely -- extruder skipping and not extruding at all.

Before I continue.  The extruder is NOT clogged in the classic sense.  I eject the filament, trim the off the part that has been through the extruder gears, then reload, the extruder primes normally and extrudes immediately.  Nor is it an idler tension issue or heat creep from the extrusion motor.   In the tripple part print that failed, the extruder gears were doing so well that the filament had "accordioned" inside the extruder tube.

Note that I said the nozzle is not clogged in the classic sense, not that its not clogging somehow.  If you look at the above, you can see that it doesn't have anything close to a good tip on it and no sign of the little string you tend to get when ejecting filament from a hot nozzle.  Yet I reloaded the filament after trimming that segment and it extruded immediately and normally.

I tried slowing everything down, dialing the print speed down by 50%.  That didn't help.  I upped the filament temperature by 5deg, didn't help.  So at this point, I switched back to a 0.4mm nozzle.  I figured I would give up a little sharpness in the corners, but overall it wouldn't impact the final result too much.

Using a 0.4mm nozzle and 0.1mm layer height was worse than the 0.25mm nozzle.  I wasn't able to complete a print without enough skipping to serious impact the print quality, or fail the print altogether.  I tried upping the print temperature by a 10deg with no luck.  I slowed the print speed even further, in the slicer, resulting in a max speed 30mm/s on fastest extrusions.  No luck.  Dialed back the retraction from the default 0.4mm to 0.2mm -- no luck.  In between a couple of failed attempts, I cleaned the extruder and did a couple of cold pulls.  This is the one place where I did see something I didn't expect.

When doing the cold pull, I was quite forceful on the filament, keeping it extruding as long as I could, down to between 165 and 170C.  What was a bit worrying is the slight ridge where the nozzle meets the heat break.  Note that this isn't an untightened nozzle.  It was tightened down in the heater block, against the heat break while hot.  It doesn't leak.  I looked at my 0.25mm nozzle and my backup 0.4mm nozzle have a slight slope on the opening that would seem to correspond to the ridge on the filament.

This, somewhat poor quality crop/zoom shows the slight angle in the nozzle opening.

No such right appears on the cleaning filament when using the same cold pull procedure.  However the cleaning filament seems to have a much sharper transition temp.  It's either soft and extruding, or not, unlike PLA that gets soft long before it will extrude.

After failing at 0.4mm/0.1mm I switched to the 0.4mm/0.15mm quality profile to see if it would at least print there.  I left everything default.  It did complete the print, with some very minor extruder skipping on the last few layers.  Here is a comparision between the 0.25mm/0.1mm (bottom) and the 0.4mm/0.15mm (top) print.

So now, I'm really running out of ideas.  I should note that the extruder skipping doesn't start near the same part of the print each time.  Sometimes it starts 20 minutes into the print, sometimes two hours.  Sometimes it starts on a wide infill layer, sometimes it starts in the detail parts.  I certainly cannot find any common thread.

While I was writing up this post, I decided to try a print with a lower temperature on the though that maybe something about this filament and/or the slower print speeds was letting the point at which it was softening move to far up into the heat break.  I went pretty fare down, 200C, from the 215C Prusament default.  That certainly didn't work.  Only made it 4-5 layers in before extrusion stopped completely.  I didn't even eject the filament to clear the jam though.  I simply hit the retract button in Octoprint, then hit the extrude button, and extrude it did, and at around 190C too, as the printer was cooling down after I canceled the print.

Tomorrow, I'm going to load up the roll of Hatchbox Silver and see if it will print successfully.  The E3D heat break does have a deburring on the throat where it meets the nozzle and the the E3D nozzle drawings also show the throat opening being tapered.  Those two would account for the ridge on the cold pull.  It lines up perfectly when measured.  The melt zone on the above cold pull extends to exactly half way into the actual break section of the heat break -- between the heater block threads and the heat sink fins.  So everything I see says the system is operating properly, and yet I can't get a high quality print out of this filament.

Thank you for reading this far and suffering through my pain with me.  I sincerely hope you have some major wisdom to share we me, and the next person who comes looking for a solution to this kind of problem.