Retraction

[atari3232 0]

I've just installed and calibrated the dual extrusion kit. It's all working perfectly for the first few layers but then it all goes wrong.

Looking at the filament it seems that after a few back/forward feeds from the extra retraction the teeth are causing the plastic to get 'fluffy', for lack of a better description, eventually leading it to just gouge out a groove and stop feeding altogether.

Cutting a short section out of the filament and switching back to a single material print and everythings fine again.

I know the extra retraction is to help with the oozing but I was wondering how everyone else is getting on? Have you changed the retraction amount? Loosened the feeder spring? Is it just the filament I'm using?

-Barry

 

[illuminarti 18]

Was everything working ok with single nozzles and retraction? If so, is it just the second feeder that's having problems now, or is the original one also having problems?

 

[atari3232 0]

Yea everything is working fine with regular retraction when printing with one nozzle. (in fact I think the act of taking it apart to install the kit has made it even better than it was before)

When doing a dual material print both heads print well if I disable retraction (but oozing gets out of control and ruins the print), both heads eventually fail to feed if it's turned on at the default value in cura.

 

[eagreen 0]

17mm retraction @ 30mm/s works pretty fine for me. feeder springs are pretty tight. maybe your retracting too fast and your feeder is grinding your filament

 

[illuminarti 18]

What retraction speed are you using?

 

[atari3232 0]

Retraction is set to 40mm/s, I presume that's the default as I cant remember changing it.

I think I may have a better idea now. It stopped feeding again but as I was pulling out the jammed filament the bowden tube popped out too, a plug had formed at the end. The alu and bottom plates are at a bit of an angle, with the nozzle side being lower than the fan side. I think the bowden tube and white connector are not meeting flush, although I thought with the new hot end design the molten plastic wasn't supposed to get that far up.

Could it be that the long retractions are pulling moltem material further up the tubes than you'd otherwise get?

I'll take the whole carridge apart and see if I can get it aligned a bit better, maybe try a spacer on the fan side threaded rods to keep the middle and bottom plates a bit more squared up.