Flow starts sputtering mid-print

Hey all,

I'm printing 100% fill with a clear ABS. The print seems to work fine for X amount of time, then starts sputtering as if it can't grab the material mid-print. If I push the filament down, it feeds for a short time, then starts to sputter again (I pushed on it directly after the sputtering in the top photo). The tension bolts that hold the filament against the hobbed bolt seem to be fine (as it will print without sputter for maybe 8 minutes), but I don't know where to go from here. Ideas?

 

The usual question in this situation is what hobbed bolt are you using? Unless Robo shipped you one that is different than the ones from the November shipment you need to replace it or you will always get this intermittently. I got this one. http://www.ebay.com/usr/easyreprap
Specify the hobb to be 15mm from the base of the bolt head. You may need a washer or two to center it and you may need to cut the extra off the end of the bolt.

Also add some more washers to the idler springs to tighten it up.

 

BTW, from the photo your Z height looks OK but a maybe a bit too low. You probably get extra material squishing out between tracks on the first layer.

 

With a good Hobbed bolt, a lot of tension on the springs and proper extruder temperature you should never see extrusion skipping or stripping of the filament. You should never see any plastic shavings on or under the bolt.

 

I received my printer towards the end of October, so this very well may be my problem. I never really saw this issue with white PLA, but it does it all the time with the clear ABS. I have a spool of black ABS I might give a shot to see if it's this particular color/spool too.

My Z height may very well be off. I've thrown the nuts on this thing several times, and have had to re-position it. Honestly ABS seems so much harder to deal with compared to PLA.

 

Hi jdumbaugh,

Another thing you can try is slowing your printer down a little bit and raising the temperature. The clear ABS is a little harder to work with and requires higher temperatures. When you speed it up that just means you need even higher temperature. The better hobbed bolt wouldn't hurt to get either.

 

What temperatures would you recommend? I've seen as low as 210C, and Cura recommends 230C for ABS

 

It truthfully depends on which company clear plastic you are using. A lot of them will come with their own recommendation, but like I said that is usually based on your speed. Check the manufacturers recommended settings and work from their. If that is what you are already using try turning up the temperature just a little bit and see how it goes.

 

I move back and forth between Cura and Repetier, and noticed that when printing in Repetier, the perimeters printed like gold, but the infill was thin. Does 60mm/s seem high for infill??? It's always worked fine before.

I ordered one of the hobbed bolts at 15mm, should have it installed next weekend.

 

What is the speed of your perimeters? If the bottom layer infill seems thin the you can slow just that down and make sure it is one 100%infill to get a solid layer. If the rest of the infill seems then you can try decreasing the speed, however I run my normal PLA prints at 70mm/s. Also, it may help to increase the infill density.

 

I think it is a combination of temperature and z height. I ran into the same issues with abs. every time i got skipping i would look at the hobbed bolt and see shavings. Cleaned it out and it would print for awhile then skip again. I raised the Z first layer clearance from .002" to .005" and raised the abs temperature by 5 deg to 235 and it worked better.
I agree that abs is harder to work with than pla but for some prints pla will not do.

 

J, the new Marlin firmware helps avoid some cases of throwing the Z nuts. It backs up to make sure the stop microswitch is off before searching downward.

 

The Z-height is tripping me out because the perimeter printed fine in Repetier, and thin / no adhesion in Cura. I keep seeing that you're supposed to make the first layer "thicker, for making it stick to the bed easier", does that mean lowering the layer height? I changed the initial layer to 0.2mm from 0.3mm and it adhered just fine, the 2nd layer wasn't bad (perimeter) but the infill was stringy. It was barely making contact by the 3rd layer

 

What is considered a "high" number for ABS? I'm printing at 235 now with the black, and it's making a popping noise?

 

Where can you get the updated firmware?

 

No - the "First layer height" setting means how thick the first layer is. Thicker like 0.3 tends to stick better.

 

I second the replacement of the hobbed bolt. Some filament just doesn't want to work very well with the stock bolt.

 

I purchased the new bolt. I'll let everyone know how that works out