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SOLVED - My printer worked, now it won't (PLA printing problems)

Posted by David J 
SOLVED - My printer worked, now it won't (PLA printing problems)
December 07, 2014 02:58PM
Prusa i3
Heated bed (PCB ) with glass on top
Greg Wade style extruder
E3D v6 hot end, 0.4mm nozzle

This is getting very frustrating! Up until yesterday my Prusa i3 would print objects in PLA with very few problems, using 185C nozzle and 60C bed temperatures. I replaced the Z-axis bearings on the X-axis assembly as I'd installed them badly and they were making a nasty noise (not any more!). Put it all back together, checked that the X-axis was level, set the Z-height and levelled the bed - but now I can't print anything at all. The initial perimeter trace just lifts off the glass plate as soon as the nozzle moves around.

I normally set the nozzle height to the thickness of a piece of paper (measured as 0.1mm), but I've tried it a little higher and a little lower - no change.
I've tried nozzle temps from 195 to 200C - no change.
I've tried a bed temp of 60 to 65C - no change.
I've tried freshly cleaned glass, then with a light coating of hair spray, and once with blue tape - no change.

The nozzle isn't blocked, as the plastic is coming out easily (as it was before the repairs). The PLA filament is being fed easily.

The main frustration is that my repairs shouldn't have changed anything to do with printing - I have made no changes in RepetierHost, or in the Cura slicer (I've also tried Slic3r). All the settings are the same as they were before - but now it won't work! angry smiley

Any advice will be gratefully received!

Edited 1 time(s). Last edit at 12/07/2014 05:18PM by David J.
Re: My printer worked, now it won't (PLA printing problems)
December 07, 2014 05:18PM
Well, I think I may have found the problem - I remembered that my multimeter came with a thermocouple, so I measured the temperature on the nozzle - I had set the system for 190C but I only got about 155C. The Prusa kit I bought had a pre-wired thermistor for the hot end, but it didn't fit very well so I fitted the one that came with the E3D hot end. E3D had changed the thermistor type when moving from the v5 to the v6 (from the EPCOS type to the104GT-2).

I modified the Marlin code from 'type 1' to 'type 5' and downloaded it to the RAMPS board - and now I get 180+C at the nozzle. I'm happy with that, as I wouldn't expect a perfect temp reading when leaning a thermocouple against the nozzle. The print is still lifting a little, but at least it's laying a good trace now, which a better place to start fixing other issues. smiling smiley

I am left with one question - why did it work before? eye rolling smiley

Edited 1 time(s). Last edit at 12/07/2014 05:20PM by David J.
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