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Underextrusion due to over retraction?

Posted: Fri Aug 12, 2016 9:47 am
by Qdeathstar
Hello, working to get my printer fully calibrated and have rant into another issue.


It seems like I am having issues with underextrusion when printing "ridges" or small areas in between large gaps. I'm thinking this could be due to the filament being retracted in between the ridges and when it moves over to the next ridge, it extrudes air for a bit causing the under extrusion?

I checked my retraction settings which haven't been changed from the defaults and it is at 6.37mm, which seems like wayy to much, from what I remember on my prussa...

Obviously this is "why not test it" theory but unfortunately I had to go and go on vacation and won't be able to play for another four whole days :(

If there are any alternate theories I'm listening as well

Here is picture where there is not a lot of retraction going on, then another picture where there is ten tons of retraction (it seems to get worse as the space between ridges increases)

Re: Underextrusion due to over retraction?

Posted: Fri Aug 12, 2016 10:00 am
by Mac The Knife
The retraction length for your Prusa would be shorter because of the shorter distance between the hot end and the extruder. The longer the path, the more the filament compresses in the bowden tube, the more retraction length needed to relieve the pressure on the hot end.

Re: Underextrusion due to over retraction?

Posted: Fri Aug 12, 2016 10:05 am
by Qdeathstar
But, do you think the longer Bowden tube would require extra push to get started again after the retraction? Right now it is set to .1mm extra after retraction... Perhaps I should increase that to .2-.3 and leave the retract at 6mm?

Re: Underextrusion due to over retraction?

Posted: Fri Aug 12, 2016 12:17 pm
by abecker
Hey Qdeathstar, I would be interested to hear what you find. Here is another post on a similar topic http://forum.seemecnc.com/viewtopic.php?f=37&t=10582

Re: Underextrusion due to over retraction?

Posted: Fri Aug 12, 2016 12:23 pm
by Qdeathstar
Yes, I saw your topic.... But you don't seem to be printing in an area with a lot of retractions...

It could be a partially clogged hot end, because at the same time, these areas are also printing slower because they are smaller.... Slower = less filament being pushed = wammo So I am going to try to clean the extruder. I only got .4mm drill bits so they'll have to do

Re: Underextrusion due to over retraction?

Posted: Mon Aug 15, 2016 9:56 pm
by Qdeathstar
So,

I stuck a .5mm drill bit into my nozzle, reduced retraction speed to 60mm/s, increased extra extrusion on retraction from .01mm to .03mm and reduced the extruders acceleration from 5500 to 3000 and those things combined turned my under-extrusion issue into a bit of an over-extrusion issue. I had decreased the filament diameter to 1.7 trying to figure out the extrusion issues so i think when i bump that up to 1.73 (measured) i will get better results.

Re: Underextrusion due to over retraction?

Posted: Mon Aug 15, 2016 11:34 pm
by Qdeathstar
Here is an aftershot:
image.jpeg

Re: Underextrusion due to over retraction?

Posted: Wed Aug 17, 2016 8:16 pm
by Sonrisa3D
This guide can help in dialing in retraction.
https://www.matterhackers.com/articles/ ... -to-oozing