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Extruder too hot?

Posted by rtrahms 
Extruder too hot?
February 02, 2013 03:35PM
Prusa Mendel i2, Wade Extruder, GT2 belts & aluminum pulleys (great, btw)
Fully calibrated X,Y,Z & E motors
3mm PLA
Slic3r
200C first layer, 190C every other layer

Very precise, but do get the occasional BLOB which is annoying (see the pic). Any suggestions here?

Thanks in advance!
Rob
Attachments:
open | download - IMG_1624_mini.jpg (118.6 KB)
Re: Extruder too hot?
February 02, 2013 07:58PM
First thing that jumps out from the picture is your bed isn't flat front to back, assuming the picture is taken from the front.
Re: Extruder too hot?
February 03, 2013 02:59AM
Hi -
Not sure I follow. Are you talking about the way the painters tape is laid down? If so, I wasn't aware front to back was important - the extruder is moving in all directions.

What I did find (check other posts) is that I had two mistakes. First, my filament width had not be set correctly based on actual filament width measure (I just had 3mm in as the parameter). Second, my glass plate only had two clips holding it on the heated bed - big mistake. I now have 8 clips, and things seem to be much better.

Thanks!
Rob
Re: Extruder too hot?
February 03, 2013 10:20PM
I think what Plygonhell is talking about is the skirt layer is not the same width as it goes around the shape indicating that the bed may not be perpendicular to the print head. Check that the nozzle is the same distance from the bed in all 4 corners for this. You can use a piece of paper to test the gap to the nozzle, and it should be the same everywhere.
I noticed you said you were using PLA, but your temps are a bit on the hot side for PLA and your part seems to have a burned filament (brown area). You do not want to burn the plastic and clog your nozzle. Although the measured temperature is not always the melt area temperature depending upon your hot-end configuration, 190-200C is closer to ABS temps. As a general guideline lower temps are better than hotter temps. The filament extruding reaches it's glass transition (freezing) temp faster and maintains its shape as formed by the nozzle. A margin above the minimum extruding temperature is a good idea- at least 10C above. There are procedures on how to find each material's desirable extrusion temp which is different from manufacturer to manufacturer and color to color.
Re: Extruder too hot?
February 13, 2013 08:23AM
190-200C is fine for PLA as long as your thermistor tables are correct and that's the actual hotend temperature.
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