Strange ABS Prints

[mhorton]

I've gotten several prints out of this printer recently with ABS and it worked fine. Recently, it started acting strange. The fill is blobby, the first layer is inconsistent, the layers separate easily after printing, and sometimes the surface comes out bubbly. Sometimes there's a slight burning smell, but I don't know if that's just the heat and hair spray or if it's really overheating the filament. I was operating at 240 degrees because I have the extruder that needs to add an extra 10 degrees. But I've gone all the way down to 225 and I'm still getting these issues.

Any ideas? See the attached photos.

mammothfail2.jpg (155.07 KiB) Viewed 7388 times

mammothfail.jpg (219.12 KiB) Viewed 7388 times

[jimc]

it sort of looks like your glass isnt flat and its printing too close to the bed in some areas OR there is an area on the glass that wasnt cleaned right or not prepped with the right amount of glue, hairspray etc which is making the abs not stick and the nozzle is dragging it around the bed.

[mhorton]

The picture of the fill is about an inch and a half above the glass. It stuck very well that time (pried it off with a razor blade), but the fill came out blobby as the picture shows. In the flat one, the object wasn't quite level, but it has printed properly before several times. I've definitely had level issues before and this is not one of them.

[jimc]

you know i was looking so close at the second pic i really ignored your first one. infill that is broken like that which usually leaves holes in top surfaces as well can be caused by a few different things. #1 too high a temp. this makes the plastic to watery and it doesnt bridge the infill very well. #2 if you are using s3d turn off the random infill placement setting. #3 use a higher infill percentage. while this can help correct the issue it doesnt really cure the problem. #4 a dirty or 1/2 clogged/tight hot end. #5 underextrusion. this can be from improperly filament dia setting, multiplier too low or too low a setting for your extrusion width....or #4. getting back on #4, do you change plastic types often? with the makergear hotend the brass tube doesnt really have a heat break in it so it has a long hot zone. different plastics tend to coat the inside of that tube every time you switch plastics. every so often you need to take that apart and clean it out or it will just get tighter and tighter over time.

[metrons]

hey jim, you mentioned taking apart the extruder every now and then and cleaning it out? i'm switching from PLA to ABS tonight and i'm wondering about cleaning that. how ofter should i? do you know of a link (with pics maybe) showing how to clean it properly?

cheers

[jimc]

If you have never changed plastics before then dont worry about it. The problem always seemed to be the constant switching back and forth.