Retraction Help

Hi, I'm very new here and to the whole 3-D printer world.... I have a problem with my firmware, and have no idea where to start.

First let me explain what has happened to bring me to this point.
Back in June of last year I bought a RepRap Prusa i3 3-D printer from China (DIY) and it worked to a "T"
some months back (about 6, give or take a little) I was trying to make some minor adjustments to the firmware, and inadvertently erased the pre-programed firmware that was on the board, so I bought a Serial - USB interface to my board (MKS Base v1.3)

I had loaded some kind of Marlin on the board and it sort of kind of worked, but more recently I had time to pick up the printing hobby again, and need the control that I had originally when I bought the printer. So I've been uploading and re-loading different firmware versions of Marlin until I found one that works and does not crash the printer when it homes and allows the "Home" to be soft and gentle. ... so now onto my current problem

I have uploaded Marlin 1.1RC1 onto my board (it's the latest version that won't crash the printer)
Everything works GREAT except ONE TINY little thing .... it retracts the filament so badly and quickly that once it retracts and goes to advance it again it is already cooled and plugs the nozzle with a solid / swollen ball of sorts (it's so bad I have to pry it out with a pick and break off the ball just to cut it off and re-feed the filament)

I NEED HELP

I've read most if not every thread on this and I can't seem to get it to work for me... Writing programs is something new for me, so any help will need to be dumbed down a bit

The filament is good, just opened it up a few wks ago and it does come out without a problem, it's just the advancement / retraction issue I'm having a very bad time with.

Thanks,
Paul

([email protected])

Edited 2 time(s). Last edit at 05/16/2016 11:09PM by pjbmac.

You can set the extrusion length and speed in your slicer.

Also see if the original manufacturer will provide the original firmware, as this seemed to work better for you - I find it shocking that the original firmware and stl's for printed parts are not supplied with the printers - its the least a manufacturer or printer builder can do to help their customers, these are not consumer machines yet.

I think configuring marlin (or other firmware) yourself is a useful exercise and will further your knowledge of how the firmware works.

But yes you can tweak your retraction settings in your slicer. You might need to adjust your e-axis max feedrate, acceleration and retract acceleration in Marlin may hlep.

Edited 1 time(s). Last edit at 05/17/2016 07:36AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

I use Cura slicer. I found a 4.5mm retraction at a 80mm/s retraction speed really gives best results with PLA at 200C

Depends on the extruder and hot end, do not use long retractions 4mm+ with e3d all metal hot ends with direct extruders and PLA, you will get jams the warm filament is pulled back into the heatbreak where it cools and jams.

On a direct extruder (i.e. no long bowden tubing) you would be better to test to see how fast your extruder can retract and aim for short-fast retractions. One method for testing maximum retract speed is to heat your hot end, then from a host like pronterface set extrusion speed to 50mm/s (i.e. 3000 mm/min in pronterface) and the ask for a 1mm or 2mm extrude, then a 1 or 2mm retract. If the extruder turns (and the motor does not stall) go faster and repeat the process with a higher speed. If the motor stalls and does not move reduce the speed and try this again. Do not do too many retracts in one go as youll pull the hot filament back up into the heatbreak and get a jam.

Once you know the maximum speed you can retract see how little length you can get away with. My idea is that 0.5mm at 200mm/s is better than 2mm at 50mm/s. You might be able to get a higher speed by increasing the motor current but don't go past the point where your motors get hot.

Once you have a setting maximising speed do some retraction test prints and increase length slightly if you're still getting an unacceptable amount of stringing.

With bowden you'll need a lot more maybe 3-4 times more than with a direct extruder but you are not actually pulling the filament back that far, the elasticity in the filament is absorbing most of your retraction. And you're having to unretract against that elasticity to continue extruding this is one of the reasons bowden just doesn't compete with direct extrusion in terms of precise filament control.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

I have an extruder with a tube that the filament runs down into and then to the tip and out. (its a .4mm nozzle) I will be uploading pictures as soon as I can to better show what is happening. Tried moving the nozzle up a little but it did not help any.... I guess I will need to sit down a bit more and try to understand some of what you guys wrote if I am off work over the weekend... my time on my printer is very limited due to my work schedule.

I've tried to get in touch with the person who I bough it off of, and they do not have an Ebay site up any longer...