Extrusion Stops

I'm having trouble keeping extrusion going. I can often get through a layer or two of printing, but extrusion just isn't reliable. I currently have the print head raised 30mm up off of the glass, just floating. I set the manual extrusion to 100mm and told it to go.

Sometimes it'll extrude through the whole 100mm, sometimes it won't. It always seems to shave off the filament so that the bolt can't grip it. I've cleaned the (flat) hobbed bolt multiple times. Maybe a concave hobbed bolt will help? Are there any other common issues that can cause this? I thought that maybe the filament was too thick, so I changed the manual feed rate to 50mm/min, but it still failed part way through.

I can always "assist" it by pushing on the filament, but I can't do this during a print as it messes up the Z-axis and, of course, if my hobbed bolt is clogged then this doesn't do me any good at all.

Edit: ABS, 220°C

 

I kept having this problem too. Finally I tightened the extruder holder to what (at the time) I thought was an excessive amount and it removed the shaving. Problem after that was it stopped shaving but then the filament fell off track after the bolt and started coming out of the extruder holder itself. It seemed liek the filament was getting backed up. I got it to work by lowering my extrusion speed to about 80%, it may work but there might be a better solution.

Are you using the stock hot end? Are you too close to the print bed (causing back up?) Could there be a partial clog in your hot end?

 

You mean you tightened the explody-screws?

I reduced it to 50% and it still stopped coming out

Stock hot end. 30mm off of the print bed (was testing to see if it would stop with nothing below it. Might be clogged I suppose.

I've tried temps up to 230°C, same results. I'll check out the eBay bolts.

 

The non-recessed bolt that came with my printer even had the teeth angled away from the feed direction so it was not even close to working. If yours is like this you need a new bolt. Make sure the bolt you order is 15mm from the bolt head base to the middle of the hobb. The sellers sometimes ask for the measurement in your order comments. You usually need to play with a washer or two or a different thickness washer to get it centered. Make sure you put a few drops of extra strength Locktite on the corners of he nut head while in the gear. Some others drill the gear and use a grubb screw. If you don't do this the nut can slip a bit back and forth in the gear on each extraction. If you use Locktite let it dry 24 hours and try not to get it on the threads.

That could be only half the problem. You should be able to push the filament though by hand with the idler bearing assembly open. It should not take a huge amount of force to get it flowing.

 

Odd, I remember replying to this yesterday. Guess I never hit the post reply button or I replied to some other thread.

Anyway, I threaded a guitar string through hot end and flossed it. After removing the string, I could no longer insert a filament into the hot end. I pulled the hot end off and a chunk of "something" fell out. I never found the chunk, but I felt it when I put my finger up where the hot end goes and I heard it fall out. Put the hot end back on and it is extruding fine now.

However, now my Y axis is WAY out of whack. Going to go to Home Depot in a few hours when they open and see if I can find some hardware that will work with Tesseract's bed leveler and a dial gauge (http://melodybliss.org/robo3d/ section B.2)

 

I am having similar issues. I can push filament through fine, but midway through prints, the hobbed bolt shreds the filament and the print dies.

I've tried upping PLA temp from 195 to 225, slowing the printer down to 10-15mm/s, switched to the recommended hobbed bolt off of eBay, and even added some washers on the extruder bolts to tighten things up a bit.

Any ideas? I can't get anything over 15 minutes or so to print properly. PLA is white from RoBo.

Example below.

 

When it fails can you halt the print, keep the temperature where it was, loosen the idler spring assembly and try to push down the filament by hand? Does it feed at a reasonable pressure or it is it just stuck? how do you unstick it? I don't have the old J Head anymore but you can look at all the threads discussing a damaged PTFE tube where the filament goes in. Robo has a video of how to disassemble and examine it.

 

Also have you checked the diameter of your filament in several places to see if it is out of spec. Also try other filament brands and colors.

 

I will do that. Maybe try some colorfabb. Unfortunately, I figured that getting my first spool from Robo would avoid this issue.

Maybe try the spool of ABS I have, or should I wait and get PLA down first?

 

I was randomly poking around the Mendel 90 blogs and found this interesting post about extrusion issues:
http://hydraraptor.blogspot.com/sea...pdated-max=2014-01-01T00:00:00Z&max-results=1

 

If you have Colorfab I would try it but use a higher temperature than regular PLA. I use 215C or so.

Don't be afraid to try ABS. Just do small test prints and use Aquanet on plain glass with >100C bed. Use a brim and expect warping on certain structures at first.

 

The experience I had was similar to yours, but it looks like some material is still coming through. In my case, it was 100% stopped. Replacing the hobbed bolt with the one from eBay fixed my extrusion issues. However, due to the terrible slides not being flat and the delamination issues, I've decided to cut my losses and quit wasting time on it.

The bed slides could be upgraded to linear rails (which I believe were in the original prototype?) but I don't know what to do about the delamination.

 

When I did the initial test prints with the blue PLA filament that came with the printer, the objects I made, though small, all came out nicely. When that ran out and I switched to a roll of white (from Robo), I never have been able print with any consistency. I've seen a few posts with problems that mentioned using the white filament. I wonder if that could be significant.

 

That's good information to know - I hit issues as soon as I switched from the Robo Blue that came with it to the Robo white...

On another note, I think I identified part of my issue. Looking at warlocke's post from hydraraptor, I noticed that there was excessive tape around the hotend that was covering part of the heat fins on the extruder.

I carefully cut the tape so it was only covering the metal part of the hotend, and I can print almost double now before I hit the same issue. It seems that the hotend is getting too warm, so the filament is softening just enough that it gets hard to push through the PTFE tube.

I'm considering creating a small fan bracket to help cool the hotend, and that might help. If I get it going, I'll put it up on Thingiverse. If that doesn't work, its off to E3D for me - I really want to be able to print and leave it without knowing that it will die between 30-40 minutes...

 

I have the newer J-head, which doesn't/shoudn't have the same PTFE issues. When I have a problem, it gets really hard to push through, but I figured out that the filament was getting too hot above the nozzle. I'm working on a couple of options to fix it.

 

hi splk3

I have the same hotend as you, the new one. Remove the pfte while it's hot and get something all the way down to the hot end and see if you have any blockages. I did this yesterday, removed a big blob of plastic that was caught between the pfte liner and the hot end. I also noticed the pfte tube had been cut at a slight angle and had rough edges. After a light hand sanding, it pushed down a little further to the hot end. I have not had a problem since. I also increased my PLA temp to 220c. It might be worth a try.

 

anoble - I checked it out and didn't have any blockage. After doing some more research, I think my issue was "jamming", where the hotend got too hot above the heater block and too much of the PLA was melting prematurely. This lines up with why I seem to jam ~40-50 minutes every time. Maybe printing faster and/or upping temperature will help keep things liquid where they should and solid where they shouldn't.

I'll try the higher temp - I'm desperate to get this working!

 

good that you are not getting blocked at the hot end anyway! I definitely noticed a big improvement when I increased my temps. I also enquired with the PLA reseller and their recommended extrusion temp is between 200-220. I was getting good results at 210-220 so fits with my results. Something else I noticed and might be worth checking out on your setup, when the fan kicks in at 100%, what happens to your extruder temp? If I start out a print at 195-200c, when the fan kicks in I will often see a 10c drop off in temp, the extruder then struggles to get back up to temp unless I drop the fan down to 85-90%. This is enough for my hot end to clog. With the increased extrusion temp I do not see this issue.