PLA Jamming below Bondtech  

Re: PLA Jamming below Bondtech

This seems to be a rather common theme I've been seeing on here, and I just changed one of my print-profiles to speed it up. (quality wasn't very important) In some ways It's still slower than the Prusa Default Profile!

First let me point out the big differences.

INFILL
Prusa = 200mm/s
Rough = 150mm/s

PEREMETER
Prusa = 45mm/s
Rough = 80mm/s

EXTERNAL PEREMETER
Prusa = 35mm/s
Rough = 50mm/s

Both of these are 0.2mm layer height.

When printing a LARGE base object. (about 100x100mm) doing the infill. (which I left at 25% accidentally, I wanted it at 15%)

I was thinking to myself. "Man, I never print fast, this thing is DESTROYING my spool!!!" At that point I thought. "Hey, Let's stick my finger on my E motor! That sounds smart!" It was totally smart. I'm guessing 140F. I think. "Wow, that's HOT... I never run it that hot!!!" So I dial the PLA temp up to 220c, up from 215c. After 2 layers, I check the motor temp, and it's cooled about 10F-15F. I was *MUCH* happier. That's when it hit me, like a brick to the face.

People love printing PLA at 195c.

I can *NOT* imagine, printing PLA @ 215c, running the default Prusa profile. I was COVERED with extrusion issues already with my profile @215c. I would think the Prusa one might leave a better surface finish given slower external speeds, but seriously, what is happening, is the E-motor is cooking itself up to 200F, and I bet the bondtech gears are breaking the glass temp of PLA.

I'm only posting this for the people that help the people who have this issue. I have a gut feeling this is EXACTLY what is happening.

I never print large objects, and generally run NOTHING faster than 100mm/s, but that's with a 0.15mm layer. And with the small parts I print, I generally never see speeds go near that, so my Emotor, never gets hot.

TL;DR
Slow your infill speeds WAY DOWN, and don't print with PLA "cold", keep the temps high.
Hot motor, makes bondtech hot.
Hot bondtech makes PLA soft.
Soft PLA makes really nasty jams.

It’s strange you post this because I was thinking about it yesterday and some previous post I’d seen and Facebook too. I’ve been having loads of problems with printing PLA, the extrusion seems all over the place. It’s some of the worst print quilty I’ve seen. But I don’t get it with PETG it seems.

I thought it was a bit strange but I believe it could be down to what you’ve just said, rather than the PLA being hard into the hotend it’s soft hence it’s affecting the extrusion.

That’s my theory I just need to install some fan on that stepper to try it out or lower the motor current a bit

Re: PLA Jamming below Bondtech

It’s strange you post this because I was thinking about it yesterday and some previous post I’d seen and Facebook too. I’ve been having loads of problems with printing PLA, the extrusion seems all over the place. It’s some of the worst print quilty I’ve seen. But I don’t get it with PETG it seems.

I thought it was a bit strange but I believe it could be down to what you’ve just said, rather than the PLA being hard into the hotend it’s soft hence it’s affecting the extrusion.

That’s my theory I just need to install some fan on that stepper to try it out or lower the motor current a bit

I don't think under-current would work. The amount of power needed to extrude through a direct drive is crazy. I was thinking putting a heat-sink on it might help. (but add massive weight to the carriage)

Honestly there's 3 solutions.

1. Print slower.
2. Print hotter.
3. Replace the extruder with some kind of "gear reduction" assembly.

Outside of those options, I don't think anything would actually work, without impacting quality... or speed.