slightly bumpy extrusion

[Darrell jan]

I recently switched from white abs to black abs. A routine thing, done many many times before (Made easier by the extruder upgrade.) But as you can see from the picture, the white abs was coming out smooth, and as it transitioned to black it got a bit bumpy. This is from using the Load Filament function. In the lower filament, I'd run the extruder for several minutes and even made a model, hoping it might get cleaned out, but it continues to look bumpy.

The models still seem fine, as seen in the other picture. Darth Vader is with 0.1mm layers, and the two owls are at 0.05mm layers. 

The black abs looks OK on the spool. I've used it before, but I don't remember the extrusion looking bumpy.

Maybe some crud is floating around in the extruder? I looked at the drive wheel and it looks nice and clean.

Darrell

[Eighty]

I'm a PLA guy, so take this for what it's worth...

I have had a few instances of lumpy extrusion in the past. In my case it was using a temp that wasn't right for the filament. For example, I was using 230C and switched colors mid-print to a filament that likes 190-200. After I cooled the temp (using the handy-dandy Sailfish temp menu), it smoothed out again.

[Dan Newman]

1. Measure the filament diameter with calipers and use that when slicing.
2. Each spool of plastic behaves differently. It's not unusual to have to
tweak settings for different plastics. And white and black ABS often behave
quite differently in my experience.

Dan

[Darrell jan]

Hmm. I guess I could try to dry out the ABS filament. But it doesn't seem to hurt the model much.

On Saturday, March 30, 2013 3:18:24 PM UTC-7, Jetguy wrote:

More likely than not, moisture in the filament. It turns to steam and
makes bubbles. Happens more with ABS than PLA.

[Eighty]

Heck, all you have to do is FROWN at PLA, and it goes limp...

[Jerry Ryle]

I think I'm seeing the same thing on a build right now. I keep hearing tiny pops and snaps and I see some lumps in each layer on my print. This same spool of ABS has been working fine. However, it's been sitting on my machine for about 2 weeks now & it's kinda humid here in San Francisco--in fact, it's raining today. I unloaded and reloaded the filament today to swap in a longer polyethylene guide tube from the hardware store (the ones that came with the 2X are a tad too short and tend to pop out). When I reloaded the filament, I saw what I thought was a constant wisp of smoke coming from the nozzle as the noodle extruded. That surprised me because I hadn't noticed smoke before. But...I'm beginning to wonder if it was steam. Is that physically possible? Before my bot arrived I'd read about ABS absorbing moisture and I honestly didn't believe it could be that bad. But I based that disbelief on nothing... : )

This forum has really been insanely helpful. Thank you guys.

On Saturday, March 30, 2013 9:21:37 PM UTC-7, Jetguy wrote:

I'm actually very sure that's the issues as looking at the single
threads of extruded filament clearly showed the bubbles.
Luckily, it's not to hard to dry out. Plus, ABS can take more heat on
the spool and not deform and stick together ruining the whole thing.
PLA, would be 10 times harder since a warm day can make it soft.

[Joseph Chiu]

The tendency for ABS to absorb water and then cause spurting in the nozzle during extrusion has been documented a lot.

Having lived in San Francisco, your post reminded me of times when it felt like *I* had absorbed moisture.  So it wouldn't surprise me that you ABS has taken in water.

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[Darrell jan]

Time to bake out my silica gel packs.