Problems printing with Prusa. Extruder issue?

Hey guys I'm having problems with my reprap.
I'm printing calibration objects and it appears to print quite well for most tests initially, but messes up after awhile.

I've recorded on instance of the problem when printing a hollow box.
Video

At about 1 minute, the left corner starts to have missing plastic. After a while of that, the nozzle will also drag around plastic as well causing quite a mess. It also doesn't do bridging very well either - which can be seen at the end.

Does anyone know what could be causing the problem?
I've checked the belts are tightened and that the bed is level.
Tried increasing the temperature from 185C to 200C and the problem still occurs. (Using PLA)

I'm using slic3r with these settings:
perimeter_speed = 30
small_perimeter_speed = 30
infill_speed = 40
solid_infill_speed = 40
top_solid_infill_speed = 50
travel_speed = 75
bridge_flow_ratio = 0.8
retract_before_travel = 2
retract_length = 0.8

Edited 2 time(s). Last edit at 07/11/2012 09:56AM by ftechz.

Are your e steps/mm calculated right? looks like too much plastic is building up and causing that corner to lift when changing z height. Another thing that might help is a fan to cool the part. I dont have much experience with PLA so hopefully someone else will chime in.

Devon

I had the same issue, solved it by printing a new carriage with fan mounts and added fans and precisely calibrating my e-steps/mm. You never want to allow your hotend to drag on plastic as it may burn and clog your nozzle.

It definitively looks too hot, so I second the suggestion of trying with a fan. 200C is pretty hot for PLA, I only use 150-185 at regular speeds. Where did you get your filament? Some suppliers recommend higher temperatures than others, so 180-200 might be fine.

Also you might have to tune your retract settings. I retract 1.5mm@15mm/s with my arcol v3.

Finding the sweet spot for long brides can take some time, but adding a fan is always a good idea. I do infill at 80, perimeters at 60 and bridges at 40mm/s.

Good idea to upload a video, much easier to troubleshoot for us then.

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-Nudel
Blog with RepRap Comic

if your using PLA and getting lifts i had the same problem

solved by using glass surface to print on set temp to 62 C

then get some PVA Glue (the white stuff) and mix it with some water untill like milk

heat the bed up to 62c then brush onto the area you are going to print it will dry to the glass very quickly and then look frosted.

reapply a new pva layer for every new print. no need to clean old off just do a new layer on top. clean with glass cleaner to remove after a day of printing

i print with PLA at 185 no problem in the past i was using 200c etc as i was reading sometimes needs hotter etc etc but pla melts really low

also PLA get a fan. will help your print loads i have mine do 3 layers without then put a computer 80mm fan on full power (12v) and have it blow onto the print from the rear of the prusa. without the pva layer on the bed though you will have lift problems with the fan on

Hey guys, Thanks for the replies - really appreciated.

I found my problem with the perimeter was actually caused by the hotend not retracting enough.
For my hotend (0.34mm) I had to increase the retraction length to 2.2mm.

I still have issues with bridging where it doesn't quite stick to the sides but a big blob gets dragged around by the hotend. Again, seen at the end of the video.


I get my PLA from DiamondAge in New Zealand. It would not print well at all below 170 C.

2.2mm is a huge retract, also suggesting that you have the hotend too hot (i.e. lots of ooze)!
A 1mm retract is usually a good starting point and after some fine tuning can be reduced.

yydoctt Wrote:
-------------------------------------------------------
> 2.2mm is a huge retract, also suggesting that you
> have the hotend too hot (i.e. lots of ooze)!
> A 1mm retract is usually a good starting point and
> after some fine tuning can be reduced.


I think so as well. I'm printing at about 185-190C already and it doesn't print well at all when I put it around 170C.
There may be other factors but since it is working I'll keep it as it is for now.

Quote
ftechz
I still have issues with bridging where it doesn't quite stick to the sides but a big blob gets dragged around by the hotend. Again, seen at the end of the video.

Did you ever solve your bridging problem? I'm dealing with the same thing (not sticking to the edges, although I'm not 100% sure its reaching the edges. The design looks like it prints into the interior perimeter a bet before the bridging starts and the interior perimeter print doesn't go so well (most of it drops down).