replaced extruder

I’ve been having some issues with first layer adherence and filament randomly stopping mid print.  All this results in broken prints, and time spent diagnosing and re-calibrating the hotend.

To this end, let’s look at the current extruder;

Note the following:

  1. Applied generous amount of JB Weld applied to the connector(I stripped the hole in the extruder, but this held the connector in place).
  2. The screw on the lip with the bearing was fully tightened, which I suspected that not enough force was being applied to the filament.
  3. The mesh of plastic zip ties holding the extruder in place

 

I selected this extruder, the SaldoT Extruder, as it had a separate piece with the bearing, which Iooked like it can apply more force to the filament.  The idea is not to apply crushing force on the passing filament(which would grind the filament instead of pushing it through), but have a wider range of force and be able to some variations to the width of the filament(hey, I use a budget brand of filament from Microcenter) tightening with springs.  The springs didn’t make sense to the original extruder, as the lip with the bearing is connected to the extruder body and flexibility is limited.

Removing the stock kossel extruder showed a bit of wear(probably from the filament that it was grinding/striping

Putting the new extruder on for sizing purposes.

Note that the spur gear is not aligned.  The simple solution is to remove and flip the spur gear upside down, as seen here;

This extruder had provisions for the connectors to screwed into both ends, so this can address the tangled filament issue that I had previously;

I printed the following mount to keep the filament neat(designed in SketchUp);

and mounted on the printer;

Finally, I used the extruder mounts(note the springs to it can better handle filament of varying thickness);As a final act(also to see if this was worth it), I printed the calibration cube.  Immediately, I noticed that the first layer was printed thinner and it stuck to the print bed,  After a few test prints, I was confident enough to print without a raft(saves some time and filament!);

And here is the new calibration cube(R) next to the old print(L);

Two differences to note;

  1. Without the raft, I can have a smoother finish on the bottom.  The left print always looked a little loose since it was printed on top of a raft)
  2. The previous extruder must have pushed out more filament(at a higher rate of the spurs grinding the filament and stopping the flow) – the skirt and raft always had loosely adhered first layer, usually by the 3rd and final layer on the raft, the raft provides a large enough surface area to stay in place for the actual model to print.  The new extruder makes the first layer much thinner, to a point where I can feel a sharp first layer.

Because of point #2, I adjusted the MANUAL_Z_HOME_POS value so the first layer isn’t smushed as much.

 

The Kossel Mini is looking nice!  Hopefully one of these days, I’ll be printing on the bare glass surface!

 

…also, gotta do something about restoring the autoprobe  feature.

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