Low extruder flow

Printing was going ok. Then on the next print the volume of extrusion was much less. I have taken the filament out and checked the geared bolt and it does not appear to be slipping (no plastic residue). There are also no signs that the filament has been eroded at the gear like it was slipping. I have reinstalled the filament several times using several different temperatures up to 230 degrees and pushing through a relatively large aount of filament. I am suspicious that there is a clog in the nozzle that is reducing the flow. The only change I made between prints was that I increased the extruder retraction length from 1 to 2mm in an effort get rid of some blobs I was getting on my prints. I'm stumped. Please help.

 

Have you checked the diameter of your filament?

 

Yes, I checked the filament diameter and it was almost exactly 1.75mm. I think I have tracked down the problem to the amount of pressure I am able to put on the filament using the latch bolts that hold the filament against the roller and hobbed bolt. I have to tighten it until the bolt hits the back face of the extruder block. At that point you can't go any tighter. My experience is that if these are not pretty tight, the filament is not fed properly into the extruder. I am consdiering getting shorter bolts that will allow me more tension range or another method of clamping the latch.

 

Can you push it through at a decent rate?

 

Yes, no problem pushing it through and it comes out at almost exactly 0.400mm. As I said in my last reply, the issue seems to be related to getting enough pressure on the filament using the supplied latch bolts. I have tightened them down to the limit where the tip of the bolt is hitting the wall on the other side. I don't know if anyone else has experienced this but I am going to get some shorter bolts and try that. Is there a danger to over tightenning? However, with the current setup and the default speeds and feed rates in Repetier host, it seems to be working OK. I suspect that if I tried to increase the speed, the tension might become critical.

 

New printers should have recessed hobbed bolts. Sounds like your assumption is correct. If you over tighten it might deform the filament before it can be properly extruded, though unlikely.

 

My printer is pretty new. I have only had it about one month. I appears to have the improved hobbed bolt. The link http://forums.robo3dprinter.com/index.php?threads/better-hobbed-bolt.846/ has a great picture showing the tips of the latch bolts hitting the interior wall beyond the nuts. I think that limits the amount of tension you can put on the filament/hobbed bolt. Maybe that is all that is required but I think it might be better if you could tighten it further.