Frustrating Filament ...

Hours later addendum: Still working perfectly. Best prints I've ever had with both small and intricate as well as large and and a bit simpler. I'll post pics after this next piece is done which may be a while. It isn't tall, but it uses the entire diagonal print space available. Oh yes - cheap out-of-spec filament still didn't work well. But the right stuff yields the good stuff.

 

So I just successfully printed a 3 hour and 35 minute print of a part for a lightsaber model I'm printing for my husband. The previous print was not successful due to under-extrusion issues. HOWEVER, what was different this time, when I pulled the filament out of the hot-end, it was NOT stuck. It came out freely.

This is different to what happened before, so it had me scratching my head since the filament was free but it was still extruding oddly.

I did notice, this time, that the bearing that is opposite hobbed bolt did not move easily or freely. I expect some resistance but this felt like it was more. So I pulled out my trusty bottle of T-9 lubricant and lubricated the bearing. I then wiped away any excess that may have landed on the face of the bearing (that rests against the filament) and cleaned that off with rubbing alcohol since the last thing we want is the filament to now slip against the bearing and get the filament coated with oil.

So I cleaned everything up. Cleaned up the shaved material from the hobbed bolt. Lubricated the bearing. Extruded some filament to make sure it was extruding right. And finally started printing. 3 hours and 35 minutes later, I had a part with no failures or under-extrusion.

Does that mean it's fixed? Only time will tell. One data point a conclusion does not make but hopefully the rest of these will also come out great.

 

Ive been fighting similar issue all day. Hobbed bold clean, bearing smooth. Noticed a few times it wasn't extruding correctly but then seemed fine manually. The nut on the hobbed bolt is kind loose in the gear, used to be tighter I thought. So there is a bit of slop there, but I have the cure for that tomorrow.

 

I have been printing up a storm. A six hour print, yesterday a 9 hour print and today there will be much more. The springs have transformed this machine into a fine tool for me. It was what I hoped for when I first considered purchasing it. Not perfect, but certainly an excellent value for the initial buy in. I've got an idea for converting the extruder feed into one that is much easier to use. Along the lines of an EZstruder, but using most of what we already have on the ROBO. Other projects come first, but I'll post it when I get there.

 

Racegrafix,
I put six drops of High Strength Locktite on the corners of the bolt in the gear. You need to let it dry 24 hours but it is removable. I would not suggest epoxy for this reason. Wrapping with electrical take would not fit and I did not trust painters tape. I bolted it to a 2x4 block to make sure it lay flat in the gear while it dried.

I also added a few washers to the springs which is the same as changing to a stiffer spring. I had to do this because I had replaced the Idler bearing with a grooved one from ebay, so these washers were needed to compensate for the groove depth and the recessed hobbed bolt's depth. I used something like this. http://www.ebay.com/itm/RepRap-Hobb...543?pt=LH_DefaultDomain_3&hash=item48603ec457. If anyone gets this make sure you carefully specify the hobb location.

 

Oh - these changes, the locktite, the new hobbed bolt and grooved bearing and the stiffer spring/washers made a huge difference in the reliability of my prints. No more extrusion gaps! Smoother sides!

 

I removed the gear and added two grub screws that tighten down onto the nut. Now you can throw the gear across the room and the nut will not move, and I can easily loosen grub screws and remove. Shoulda came that way honestly.

Went to stiffer springs, fixed nut, good hobbed bold, clean, and still have extrusion issues lately on ABS and PLA. I think I need to take apart e3d and see whats up.

 

For reference, if you don't have a 2mm drill bit, 5/64= 1.9844mm. Cleans out the e3d nicely. Just finished a 10 hour print that was perfect until the final 4 layers - the x pulley slipped on the stepper shaft. Fortunately, this won't affect the use of the print. Even better, the extruder continues to work perfectly.

 

Up to its old tricks last night, my ROBO failed a 5 hour print due to filament feed and clog. As with others above in thread, I discovered way too much play between the hobbed bolt nut and the extruder gear it holds. I was able to shim two sides (glue wouldn't do it in the long term) of the nut with some brass, cleaned lubed and reassembled and working great right now. I should probably print a new gear. I can see no other area that needs attention in the extruder set up. Next stop, Bowden if this doesn't work out. Once I have caught up on my own projects, I will work on my idea for modifying this assembly into a quick release feed to facilitate filament changes. Or not. If I change to a different extrusion system. I'm pretty much done with this issue at them moment. Sucks.

 

I put two grub screws in gear...that's the end all solution.

 

Racegrafix, you are absolutely right about the grub screws being a much better solution than my shims. I should have read your post first.
Now, the bad news is that it still didn't completely solve my feed issues. Sweeet. I had an extra grooved hobbed bolt and as it was the only thing I had yet to change out, I thought I'd give it a try despite the fact fact there was already one on the machine when I received it. Night and day difference from the very beginning. Though I was getting a few hours of successful prints each time I made a change, or lubed, or sprung, or drilled, I was soon back to the old problems. Anyway, it is printing better than ever (the new Marlin settings seem to have improved things as well. Nice, clean and consistent layers) and I will not claim a thread ending this time. I just hope it to be so. Since well before Christmas this has been my never-ending thread. It's a love/hate thing, y'know?