Printing Issues with Rep 2

[Alistair Milne]

Hello All

Firstly I am new to the group so apologies if this has been covered before. I've tried to read through most of the posts and can't find a solution. I have a rep 2 with 776 hours build time on it. I had no issues with it outside the usual ones, occasional clogs, levelling issues etc. However recently I have been getting a lot of air prints, in fact almost everyone. The symptoms seem to relate to heat creep but I just don't know if that is the actual issue. The prints generally fail about 20/30 mins in when the PLA starts to get really whispy. I have checked that the extruder fan is mounted the right way round and that the filament is of a uniform diameter over length. I have also checked it on various filament rolls with the same results. There was one roll of Hatchbox filament which did complete a print but the finish was not as it used to be with clearly visible layers of different colour variation. I was printing green and some of the layers looked almost white.

The aluminium bar mount does feel warm to the touch but doesn't seem overly hot. The strange thing that I had not noticed before is that the stepper motors seem to be getting very hot. It is all the motors, including the extruder motor. Could this cause the heat creep in the PLA within the thermal barrier tube? 

Has anyone else had this issue and found the reason why?

Also I have already done the following: checked filament, tried various temperatures ranging from 190 - 230, changed nozzle and cleaned drive gear. I am now stuck where to go next?

Thanks in advance.

Alistair

[TobyCWood]

I always start by measuring the filament. Get a digital caliper and measure it at the point where it fails all around then up a bit. Filament that is not within .02 of 1.75mm or filament that is too oval can be a problem.... thankfully this problem is diminishing these days.

Heat creep in a Rep2 or a Mk7/8 extruder has a classic symptom. Look for an enlarged and VERY smooth surface on the filament by the tip after you carefully "Unload" it.. If it is heat creep then the stuff softened in the tube and was compressed into the sides of the tube.

But... that is not necessarily the problem. It could also very easily be that the feeder arm is not pressing the filament against the hobbed gear with the right amount of pressure. So the next step is to extrude during a filament "Load" and try to stop it from extruding by holding the filament with your fingers tight and listen for stepper stutter. If the stepper misses steps because of your holding the filament then it is probably not the feeder assembly.

Next would be the nozzle. Does the extrusions during "Load" go straight down? If they string to the side or even upward then you have hard plastic inside the hotend that is obstructing the flow. That needs to be cleared. a high "e" guitar string works well for that. 

[TobyCWood]

and... thanks...

Segment fodder for the podcast!

[Joseph Chiu (Toybuilder)]

Have you recently experimented with non-PLA filament on your Rep 2, something that would have been white-ish?  If you had some residual filament from a spool that normally runs hotter than your usual temp for PLA, there's a chance that residue is occasionally flaking off and entering your nozzle at times and plugging it.

If you have a picture of that green-and-white print, that would be interesting to look at!