Dark spots in white ABS print  

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JonPointer
(@jonpointer)
Eminent Member

I am printing white Hatchbox ABS and getting occasional dark spots.  The surface shown has a slight slant to it, so it prints in stepping levels.  What happens is occasionally one of the layers has  bit of a clump that is kind of burnt looking.  Then it gets printed over.  The part is dimensionally good and the end top surface is fine, but it is discolored by the dark spot under the surface.  Any ideas how to keep this from happening?  This is a part I sell, so the dark spots is a problem. 

Thanks!
Jon

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Posted : 04/08/2020 6:46 pm
cwbullet
(@cwbullet)
Illustrious Member

That burned filament coming off you hotend.  Check to make sure your heartbreak or heat block are not oozing.  

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Chuck H
3D Printer Review Blog...
Posted : 04/08/2020 9:11 pm
jsw
 jsw
(@jsw)
Noble Member

I've seen this in translucent PETg, and agree, it's 'boogers' on and around the nozzle falling off onto the print.

I'm in the habit of brushing off the nozzle area prior to most prints.

Posted : 05/08/2020 12:19 am
JonPointer
(@jonpointer)
Eminent Member

@charles-h13

Thank you! I will check that out!

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Posted : 05/08/2020 1:25 am
JonPointer
(@jonpointer)
Eminent Member

@jsw

Yes, I see it a lot with my translucent Taulman Bridge Nylon too.  I usually brush off a lot after switching from black, but sounds like I should also do it regularly between prints.
Thanks!

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Posted : 05/08/2020 1:26 am
jsw
 jsw
(@jsw)
Noble Member

At least look at the nozzle before a print.  Large 'boogers' will be obvious, but sometimes small blobs are hiding out of the line of sight.

Yes, I've learned by having blobs contaminate the print, or pull the skirt or first layer from the print bed.  Sometimes, you get lucky and see the blob embedded in the priming line.

Posted : 05/08/2020 2:08 am
JonPointer
(@jonpointer)
Eminent Member

@jsw

I brushed things off and got a good print last night.  However, I also noticed that during the first layer it looks like a blob was forming in front of the nozzle - like pushing up material as it went along on the first layer.  So, when the first layer was done, I paused the print, raised the Z axis, brushed the blob off the nozzle, and then resumed the print.  All turned out OK.  Maybe this means that my first layer level is set too low?

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Posted : 05/08/2020 5:10 pm
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