Help me diagnose a print issue, please

Ok, so I finally got my Prusa i3 Rework up and running, but I'm having some issues with my prints. It seems to be scorching the PLA on one side, and there's also some kind of drift or lean happening:

The scorching:
http://i.imgur.com/rHJw0V9.jpg


The lean:

http://i.imgur.com/TVzoVEu.jpg

I've got a Jhead, .3mm nozzle, 1.75mm filament. I've tried a bunch of settings, but this last one was printing at 185 deg, 60 deg hot bed, 25% fill (honeycomb). I obviously don't want to try printing anything bigger until I figure this out.

Thanks!

I don't think you need to use the heated bed when printing PLA - the combined heat of the extruder and the bed might be causing your scorching issues and remelting the plastic to cause the slumping.

Andrew Werby
www.computersculpture.com

Quote:

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Originally Posted by awerby

I don't think you need to use the heated bed when printing PLA - the combined heat of the extruder and the bed might be causing your scorching issues and remelting the plastic to cause the slumping.

Andrew Werby
www.computersculpture.com

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Ok, I'll give it a shot without the bed. Thanks!

Didn't quite fix the problem. I'm still getting scorch marks on the side, though the leaning seems to have gone away.

Ideas?

Put a pause in between each layer to let the part cool slightly. Some people simply put more parts on the bed or even just have a cylendrical "cooling tower" on the bed to get the same effect without having to directly mess with the g-code.

Quote:

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Originally Posted by Feign

Put a pause in between each layer to let the part cool slightly. Some people simply put more parts on the bed or even just have a cylendrical "cooling tower" on the bed to get the same effect without having to directly mess with the g-code.

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Ok... so how do I do that?

I wouldn't turn off the heated bed. It won't be contributing to the scorch marks and will help prevent lift. Make sure it's not set to high though - about 60c will be OK.

Regarding the scorch marks, they're caused by the head remaining in one spot for too long. The cooling tower is a good idea, but is more for when you're printing tall skinny pieces. You should not be seeing scorch marks with a normal print.

What temperature are you printing at? Too high may be causing the scorch. 185c with PLA works well for me. Also, if you're over extruding, the head may be dragging through a previous layer and causing it to scorch. This might happen most often if you're getting beads where a layer starts/ends and the head drags through them. Check if you have randomized start/end points turned on in your slicer settings and turn it on if it isn't.

Apart from the scorch marks, your print looks pretty clean. Check your print temps, make sure you're not over-extruding by calibrating e-steps per mm (check the reprap wiki calibration guide) and randmize your start/end points and you should be OK.

Also on the scorch marks... Some times you get some filament that is stuck to the nozzle for a long time. It scorches. And then later it gets rubbed off onto the print. It maybe the nozzle is not staying in one place too long but it is dirty and 'wipes' itself clean on your print.

I was printing at 185 for the first layer, dropping to 180 after that.

I think you're right about the nozzle being dirty, for a couple of reasons. First, I didn't have this issue the first few prints I did, and second, it appears to be clogged now. I'm working on unclogging it at the moment, but it was curling the filament as it exited the nozzle, and getting all over the hot end.