Extruder gear slipping

Like Gordym says it has no flat spot, this would be a great thing for the folks at SD to change or if you are adventurous with a dremel tool and small grinding wheel.....
The easiest way to get better access to the setscrew is to remove the thumbscrew/nut on the filament tensioner and that can hinge out of the way for good access to the right side of the extruder drive roller.

I thought the same thing but the acrylic outer layer around that 'gear' of my print head is closed on the side where that assembly pivots.  I could probably drill/melt a hole in there or grind away the back of that side of the extruder but before I do that I found some hex keys with the balls on the end that I will give a shot.

I removed the 'gear' today and the shaft of the extruder stepper clearly has some wear on it.  The hex set screw does not appear to be fully tapped through the 'gear' either that or this is a conical taper.  As a result it leaves very little 'bite' for the screw into the shaft.  Though that little bit is probably just enough once it starts to slip there's a risk of scoring the shaft and I can feel some scoring on the stepper shaft (very little but it's there).

I removed the 3 (it looks like there should have been 4) metric 2.5mm screws that held the extruder stepper to the extruder assembly and having lifted some stray yellow Kapton tape I've slipped the stepper out the back of the extruder assembly and disconnected a few wires.  Having now reviewed this it appears that from slipping either the 'gear' moved forward so it was 1/8" from the from the extruder acrylic and not flush as described above or it was moved by the previous owner probably because it was slipping (LOL...a little tinkering require eh?).  I see from looking down the lowered bearing compression arm (tension arm as it has also been called) that with the 'gear' basically flush to the front of the extruder acrylic the knurled surface is lined up with the center of the bearing surface (probably why I noted that bearing slipping).  With the stepper now out of the extruder but still connected to the machine assembly (I disconnected the stepper from the PCB so it can't run as a generator) I am going to cover the machine with some wood or cardboard and use a rotary tool to clean up the shaft.  I used a 1.5mm hex key to work the set screw in and out of the 'gear' a few times till it further intrudes on the hollow in the 'gear' (I am reluctant to try to tap this hole and the set screw is plenty durable to work the threads a little deeper).  I can honestly say that while you can probably tweak the set screw with the ball ended hex key while the motor is installed in the extruder with an unflatted shaft I don't see how you can really expect to exert the torque required to dig the set screw into the shaft as this would require to be useful (you don't want it to score around the shaft just the spot where it was tighted because with no flat that's all you can do).

I cut down a card board box into a tray.  Took my rotary tool with a wire brush.  Put on some safety glasses (spinning little bits of wire flying around near your face >no Darwin Awards to be earned here< use safety glasses).  Cleaned up the shaft of the extruder stepper.  Then I changed out for a small grinding wheel about 1/2" x 1/2".  I went parallel to the stepper shaft at first to establish a line (lightly).  Then I went perpendicular to the shaft and ground a flat about as wide as the diameter of the set screw shaft.  Since the grinding wheel has a diameter I can't go perpendicular up to the face of the motor so it tapers back up but that should not matter.  I put the wire wheel back in and cleaned up the shaft and the flat.  I then hit that flat with some 400 grit sand paper parallel to the axis.  I then reduced down to 220 grit.  Then back to the wire wheel for the entire shaft.  I put on the gear and screwed in the set screw enough I could be sure that the set screw engaged the edges of the flat.  Then I tightened it up.  I need to finish installing it.  Then I'll post some pictures.

And now I laugh my butt off because I just noticed as I resinstalled the stepper motor that the 'missing' screw someone took out and put in the wrong hole long before me.  More over the nuts that hold the extruder on are no where to be found (they were never there).  Nothing like a tire with no lug nuts.  I guess the extruder stayed on merely from the cable tension before.  Off to go find me some metric hardware.

A local hardware store to the rescue.  Lowes has M3 pan head holts but not cap screws and no nuts or washers of any type (makes perfect sense!).  Home Depot was a strike out.  I went down to the local hardware store and asked the counter and they had not just the nuts, but all sorts of washers which fixed this right up.

I left the 2 bolts that hold the extruder to the carraige loose and put in the 4 bolts that hold the stepper motor assembly to the extruder.  I left those 2 bolts loose as the acrylic holes for the stepper are very close and I wanted some wiggle room.  I put in 2 bolts in the 2 opposing corners but did not tighten them.  Then the other 2 bolts.  Then I cross pattern tightened.  When that was done I tighted up the 2 bolts that hold the assemlby to the carraige.  The 'gear' is stickng out about the height of a piece of paper from the extruder which has more to do with me putting it on the shaft when the extruder acrylic plates were not compressed by all the screws than anything else.  I was able to completely tighten the compression screw (tensioner) screw without the 'gear' slipping on the stepper shaft and no filament.

I can extrude with the compression screw all the way tightened with complete positive traction.  That is entirely unnecessary but just a test to see if this works as well as I expected it would.  In fact, it might be working almost too well.  Now I get way more than 1mm of output material when I extrude 1mm so now I must tweak settings.

I had raised the extruder temperature to 205 degrees previously because originally with a slipping extruder stepper I had to almost reduce the ABS to liquid to get anything out (yes I know that is not recommended but I have an IR heat gun and frequently turn off the hot end).  Now I have more than adequate force.  So I reduced the temperature to 200.  I also raised the bed temperature to 95.  I had the compression arm (tensioner) set to about 1/8" of the screw showing...which is very little pressure on the filament).  I just printed a 'companion cube' I sliced up from Thingiverse.  It's a bit messed up but I suspect the issue is more the way it was sliced than the printer.  All in all this worked out great.  I clearly got a nice even flow ouf the extruder.  Pictures will follow later.

You got this fixed?

Here are some pictures of my work.  Sorry some of the close-up are a little blurry.