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Weird blobbyness on certain layers

by Moose_Inthe_Room

I've run into a problem with my printrbot I can't figure out how to fix. I've hunted around on forums a bit, but I only found one other person who had what might be the same issue (his pictures weren't very good so I couldn't tell for sure) but none of the fixes suggested there have worked for me.
Okay so the lead up to the problem starting: I recently got fed up with the whole painter's tape thing and installed a BuildTak sheet on my 2014 printrbot simple metal. It has sustained some minor damage from accidental homing of the nozzle when it was hot and incorrect z-offsets, but it's still in pretty good shape so I don't see how it could be causing my problem. Shortly after I had the buildtak installed and had figured out my new z-offset, my z-axis stopped working. I did some diagnostics (uncoupled the motor and found that the motor wouldn't turn at the right speed so the problem had to be either the motor or the controller. Switched out which motor was plugged into which port and found that nothing plugged into the z port would work so the problem was with the board) and found a thread on the problem. The thread suggested I reflash my firmware so I did (it seemed intimidating but it was much easier than I expected.) And it worked too!
Or so I thought. On my next print (http://www.thingiverse.com/make:131111 I had printed them out before but lost one so I needed another) my first layer went down fine, but the next half-dozen or so were incredibly blobby and uneven. The hotend would actually be jostled up and down during a layer by the uneven surface of the last one! I let it run just to see what happened and eventually the layers started evening out and went back to normal. The blobby first layers are mushroomed out to such an extent that nothing I print will fit like it's supposed to. I've also just noticed while writing this that the new prints are significantly shorter z-wise than my old ones. I've played around with my z-offset, my printing temperature, and even switched filaments, but nothing changes.

TL;DR reflashed firmware to fix something else, first layer now comes out fine, next couple are incredibly blobby.

Here are the pics, far left is the print I did before the problem started, middle is after with the same filament, right is after but with a different filament. The old print was scaled 130% on the x-axis but not changed on the z-axis, so that doesn't explain the height difference.
http://imgur.com/1pdy6h9
http://imgur.com/sft1gkH
http://imgur.com/aLy0Txw

Edit: I realized I forgot to resolve this issue, so I'm going to do that now. I wound up fixing the issue entirely by accident. The computer I use with my printer is given to me by my university, and every year I have to turn it over for a "software refresh," basically they wipe the whole thing, make sure it's running (relatively) smoothly, install software I need for my program, and then give it back to me so I can re-install other software and restore my files. So in this process my host software and all the relevant drivers were removed. When I reinstalled them and when I tried a print, it worked just fine with no trace of the weird blobbyness. A few months later the issue resurfaced and I solved it by (IIRC, like I said, I should have updated this sooner) reinstalling repetier again. I don't know what the exact issue was, but I'm just going to chalk it up to software weirdness and try to fix it the same way if it ever comes up again. Thank you for all your help, and if anyone is reading this because they had the same issue, try reinstalling your software and I wish you the best of luck!
Relevant xkcd

PrintrBot Simple Metal Small Feet
by flaagan
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Printrbot Out of Business!

by Juggala

Does anyone know where to get hot ends and other parts now that Printrbot is shut down?

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Optimal Cura Settings

by PacoDeth

Had the 3D Printer packed up for a bit after a move, getting back into using it again. Anyone have some perfected settings for Cura for the Printerbot Simple Metal? As many details as possible (pictures even!) would be greatly appreciated.

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Extended bed G-code

by europa1

Hi I recently changed my printrboard to a rev. F6 and lost my G-code that accounted for the bed upgrade. Does anyone know the G-code?

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Suddenly stringing/blobbing

by Cretemonkey

I have been printing 6 sided dice sets with ABS for about a year and suddenly, after a break of about a month, I started getting bad stringing between the dice. I have a Printrbot Simple Metal with a Ubis 13S hot end using Cura 15.04 and 75% infill. The following is what I've done to try and correct the problem.

  • print speed is 50mm/s
  • print with brand new filament
  • reduce temp down to 220
  • raise temp up to 240
  • increase retraction speed to 90mm/s
  • decrease retraction min extrude length to 0.5mm
  • increase travel speed to 200mm/s
  • triple check filament diameter (I even increased and decreased by up to 2mm anyway just to see what it would do)
  • decrease flow rate to 90% (any lower and there are gaps in the die)
  • print with fan on at 0.5mm
  • print with fan off

I may have fiddled with other things but I've been messing with it for a few months and may have forgotten something. In the end I've reduced the stringing but the blobs are still pretty bad and it takes a lot of finishing work to fix the print. Any thoughts or suggestions are very welcome even if I may have tried it you may have a better combination of actions. Thanks!

Blob Stringing
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