stringy voronoi print

tried printing one of those voronoi sculptures (quite small), it's ended up being reallllly stringy.

I tried printing a larger sculpture of a similar design but slightly larger and it worked ok so im guess it's because this particular print was so small.

I have my retraction set to 4mm I believe.

What extruder temperatures are you using? Stringy prints can be a sign that the extruder temp is too high. For PLA I use 195C first layer and 190C for the rest, but many folks here use lower.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

i think for this particular pla i have it set at 185... good point thought, will try a lower temp print..

on the retraction option should i retract on the Z axis at all?

Retraction helps prevent blobs and oozing, so I use 4mm retraction.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yea, on the retraction i have it set at 4mm length retraction but there is a Z axis retraction option which i've never used...

I'm not using the Z retraction, but I have enabled the "wipe while retracting" flag. If I understood it correctly, without it checked the extruder will stay in place, retract filament, and then move. With it checked, it will just start the move to wherever it's going, and retract while moving, so anything that does leak out will be "to the side" (usually outside the perimeter, or just getting lost in the infill). With that, there should be less risk of a blob along the perimeter, but I guess that could still lead to some "stringiness".

Regarding the temperatures, you can't really count on the values being too accurate. All thermistors have some uncertainty to them and the firmware just has a table for whatever is the nominal values. The actual temperature of a given temperature setting might vary by a few degrees between printers (when I set it to 190 I might get 185 while you get 195). You can either spend a lot of effort with an accurate thermometers, measure and adjust the firmware table, or just find whatever "temperature number setting" works well and run with that. Since the optimal print temperature varies with other factors (filament quality, nozzle size, slicer settings), there isn't that much value in having an accurate measurement, other than that it feels good to have it done right. In any case, the "delta" should be more accurate, changing the setting by 5 degrees should mean a change of very close to 5 degrees of "actual temperature".

With ABS prints, strings are easily removed by dunking or wiping down the print with acetone. Fine strings dissolve away in seconds, and it also gives the surfaces a bit of a polished appearance.

Dave
(#106)

Have you set the retraction speed to 45mm/s ?

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@ jstck - Ahhh didn't know about that "wipe while retracting" option, I think for this particular print it would maake it worse (its a really thin wall with next to no infill & visible from both sides) will try that on future prints though!
also thats a very good point about the temperature differentiations, i think i've printed as low as 180 degerees but stopped as i was worried about trying to extrude solid filament.

@ dmould - Not printed in ABS yet, have heard about those benefits but also heard its a bit harder to print in??

@ KimBrown - Ill have to check that tonight, can't remember off hand. It does retract very quickly.

Edited 1 time(s). Last edit at 04/23/2014 10:12AM by 88Zombies.

Quote
88Zombies
@ dmould - Not printed in ABS yet, have heard about those benefits but also heard its a bit harder to print in??

The main thing is that you need to print the X carriage, extruder and all hotend parts as the very first ABS prints you make, because the increased heat needed for ABS printing will deform the supplied PLA parts after several hours of printing, so they must be replaced with ABS before they get too bad for the printer to work (it may be prudent to first print those parts in PLA so you have spares in case they deform before your ABS replacements are finished). The hotter melting point of ABS means that it suffers increased shrinkage, and so extra care must be taken to stop the print warping (especially on larger parts), although that is not particularly difficult to achieve.

Dave
(#106)