Welcome! Log In Create A New Profile


Retraction calibration issues printing with my Prusa

Posted by RP Iron Man 
Retraction calibration issues printing with my Prusa
September 25, 2012 11:18PM
Hello World!

This is my first post on the RepRap forums smiling smiley

I have finally finished setting up my Prusa Mendel printer, but I have been having trouble perfecting my prints due to an issue with my extruder retraction. The problem is that during non-print moves the extruder is not retracting filament. However, after the non-print move is completed, the extruder extrudes an extra length of filament to compensate for the length of filament that should have been retracted. Since the the filament is not initially retracted, each non-print move results in extra filament being extruded, which makes my prints look like bloated blobs of plastic. I have no idea how to fix this.

Here is some background information.

I am using RAMPS+Pollulu Motor Drivers, Repetier Host Firmware, Slic3r, Wade's Extruder, and MK2 Heatbed with Glass surface covered in green tape.

Print Settings:

Nozzle Diameter: 0.34 mm
Filament Size: 1.75 mm

Perimeters: 25 mm/s
Small Perimeters: 20 mm/s
External Perimeters: 100%
Infill: 30 mm/s
Solid Infill: 25 mm/s
Top Solid Infill: 50%
Bridges: 20 mm/s
Travel: 50 mm/s
First Layer: 50%

Fill Density: 0.2


Ok, so for my first print, I did not change the default much so my retraction settings looked like this:


Length: 2.5 mm
Speed: 30 mm/s
Extra length on Restart: 0 mm
Min Travel after Retraction: 2 mm

The result was not pretty. Here is a picture of my first print:



After printing another blob, I deduced that the problem was that too much filament was being extruded to compensate for retraction during printing. Oddly, my setting for "Extra Length on Restart" (after retraction) was set to zero. This did not make sense, so I decided to avoid the problem altogether by simply disabling retraction. The result was great other than the strings of plastic left all over the part. This imperfection was something that was supposed to be solved by using retraction during printing.

Here is a picture of my second print with retraction disabled:



I decided to try to calibrate my retraction settings once again to fix the problem of strings all over my print. My attempt at printing with mild retraction. The picture says it all... A blob-like print with strings of plastic all over it. In short, neither problem was solved.


Length: 1.5 mm
Speed: 30mm/s (I have tried different speeds with the same result)
Extra Length on Restart: 0 mm
Min Travel after Retraction: 2 mm

Here is the picture:


...and here are a few more detailed pictures:




Finally, here is a (mediocre quality) video of my Prusa printing Attempt#3 that illustrates the problem:



At this point, I have no idea what is wrong with my printer. Is it my firmware? Is it Slic3r? It seems like my printer cannot retract during printing, even though I can easily retract filament using the manual control interface. I hope I gave enough information for you guys to understand what my problem is. I really hope someone can help me fix this.

Thanks in advance to the RepRap community for being so supportive!

Re: Retraction calibration issues printing with my Prusa
September 26, 2012 02:10AM
The extruder is likely stalling on the retract.
Try turning down the speed to say 15mm/s.
Try turning up the pot on the extruder driver very slightly.
Re: Retraction calibration issues printing with my Prusa
September 26, 2012 08:29PM
I tried doing what you said. I turned up the pot and decreased the speed from 30mm/s to 15mm/s. Unfortunately, the problem persisted. Also, my extruder motor pot is at the maximum current now so I cannot try to turn up the pot any more.

However, this time my print was not as bad as before. I noticed that during the print, there were times when the extruder actually retracted the filament during the non-print moves. Unfortunately, this did not happen very consistently.

Do you have any other ideas as to what the problem may be? Like I said, I cannot turn the extruder motor current up any more. Also, I can easily manually retract using the buttons without any stalling so I don't know if the current is the problem.

Anyway, thank you for you input on my printing problem. Please let me know if you have any other ideas.

Re: Retraction calibration issues printing with my Prusa
September 26, 2012 09:41PM
Then it's probably too high, it should be closer to 1/4-1/2, too high can cause missed steps as easily as too low.
Re: Retraction calibration issues printing with my Prusa
September 27, 2012 01:59AM
Also, check that the grub screws on the two gears are done up tightly.

Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9
Re: Retraction calibration issues printing with my Prusa
September 27, 2012 01:27PM
It looks to me like you have way to much filament pushing out.
1. In pronterface/printrun/whatever raise you z axes up a little.
2. Turn on heat to extruder
3. I used a metal runler I have with mm on it and stand it up and down on top the aread where your filament first enters the extruder and make a mark with a magic marker at 100mm.
4. Extrude 5mm at a time 10 times to get 50mm extruded. I personally give it a couple of seconds between 5mm extrudes to make sure i do not outrun it.
5. Measure from the same point on the top of the extruder keeping the filament straight to your mark. You extruded 50mm so you should be 50mm from your mark.
6. if your measurement to the line is 49 or less you should calibrate your e axis.
7. Next thing to consider is your filament size itself. Take a measurement with a set of calipers in mm or standard and convert to mm in 3 places in your spool and see what you measure. I use 3mm filament and my setting ended up being 2.84. Adjust your filament size in slic3r as it will be creating your gcode that manages the output. If you are using slic3r, it really does all the work for you except for temperature if you leave that set to 0, which I do so I can adjust it in pronterface. Pronterface/printrun just reads the gcode that was created in slic3r and tells it everything to do including everything unless you set heat to 0 and then you can just manually make it what you want in pronterface. NOTE: Make sure you use the flat part of the calipers to do your measurement and try to be flat on the filament. I know it's not easy because your filament is curled but do not use the very end that you would normally use on the calipers becasue its easy to cut into the filament a little and cause your measurements to be off. The filament measurement is very very important and so is the extruder output.

8. Let us know what you come up with. If you need help with the calibration of the extruder let me know to. I had issues when I reciently went live and people in here weree great and I want to pass on what I have learned.
9. Just as an fyi. If you have a ton of filament ready to push out and it does not have room to push it out, retraction will not help much. To much is too much.

Re: Retraction calibration issues printing with my Prusa
September 27, 2012 11:23PM
I finally found a fix! Thanks to everyone for the help. I case any of you are curious, here is the link (the fix was suggested in the Slic3r forum thread):


Re: Retraction calibration issues printing with my Prusa
August 17, 2014 09:45AM
thanks for sharing
Sorry, only registered users may post in this forum.

Click here to login