More ABS Problems

[CCRN]

Please take a look at the attached picture. There is a small 3/4 inch section in the middle of my bed that is not extruding or the nozzle is coming closer to the bed not allowing filament to extrude. It has happened a few times in the same place which led me to re-level. I don't have much experience with ABS filament and would appreciate a look and thoughts.

Thank you!

[jimc]

looks like there is a spot on the kapton that is missing adhesive and you have no adhesion in that clear spot on the bed. if the filament doesnt stick then the nozzle will just drag it

[Jules]

Yep, might be a bubble.

[CCRN]

That is the MIC6 PEI plate I bought from insta. PLA sticks there just fine.

[insta]

Did you scuff the PEI? Some sheets need it. I didn't do it unilaterally because it's easy enough to do when you need to, and the glossy surface is nice until then.

edit: I swear if that's another bubble

[Jules]

If it is a bubble, has anyone tried sticking a heated needle in it to let the air out? (Might leave a tiny divot.)

Definitely want to try scuffing first.

[CCRN]

Did you scuff the PEI? Some sheets need it. I didn't do it unilaterally because it's easy enough to do when you need to, and the glossy surface is nice until then.

edit: I swear if that's another bubble

I have scuffed with 1000 grit sand paper and there is no longer any gloss to the surface. Wiped with damp paper towel and then cleaned with IPA. The bed has been re-leveled and z adjust set.

There is a bit of a popping in the middle when it is cool, but it seems to go away when heated, so I think there is a "small" bubble under that spot. I ran my same gcode except for reducing temps and the PLA printed over this space where abs did not. Going to try abs again.

[CCRN]

My design in abs still has that thinning when going over this spot on the bed. I decided to shift the print to the left and now the skirt is thin on this spot. Seems like it may be raised a bit causing the filament to thin out. I still don't understand why PLA doesn't thin out, but ABS does.

I think I will put glass/hairspray back on the bed and see if there is a difference.

[ksevcik]

My design in abs still has that thinning when going over this spot on the bed. I decided to shift the print to the left and now the skirt is thin on this spot. Seems like it may be raised a bit causing the filament to thin out. I still don't understand why PLA doesn't thin out, but ABS does.

If it's a bubble, I'd assume it's because the bed's at a higher temperature for ABS. The gas laws say higher temp = more pressure or volume, so the bubble is bigger at higher temp. So a higher spot and more thinning. If you're going to try Jule's idea of popping it with a heated needle, I'd do it with the bed preheated to ABS temps or a little higher if you can manage.

[CCRN]

I looked closer at it while hot and there is a bubble in the trouble spot. Insta, let me know if there is a fix to this or if I need a replacement.