First Tryout of the Extruder

Gantry Progress

  • Installed Pronterface (Printrun) on the Gantry PC
  • Tested the fit of the Lee-Wade extruder on the tooling plated I had fabricated, it was really good, with just the right amount of clearance to the gantry but not too much.
  • Ran Pronterface through the Ramps 1.4 to test the extruder and heater.  The stepper got hot so turned back the amps on the Pololu motor driver.
  • Ran the heater up by progressive steps to break in the refractory glue.  Ended with it at 230 Deg C before putting 1.75mm abs filament into it.  Did some test extrusion, that was pretty cool.   I had it hot for a little too long and was trying to take pictures, then ran the short filament out without noticing and had a situation where it wouldn't feed new filament in correctly to push out.   Did a shutdown and later disassembled and found that the ABS had melted up to the end of the brass nozzle.  (See pic)
  • Added a heat sink to the nozzle, specially made the nozzle longer (1.5") so I could add a heat sink and now have some cause to.  The plan is that the heater heats the tip and the heat sink pulls heat out away from the tip so material will not melt all the way up the brass nozzle and gunk everything up.
  • Another thing that was not quite right about the setup is that the plastic frame has a hole for the filament sized for 3mm whereas now I am trying to run 1.75mm material.  The hole leading up to the PTFE barrel is 3mm.   This creates a ledge between the diameters that I think the filament can hang up on .  My attempted solution is to add a bushing from the 3mm hole to close it down to 1.75mm.    It seems to make the transition smooth but will see how it goes.  I turned it from 1/4-20 brass threaded rod, something I have plenty of right now.  I could have made a new frame but I thought that would be wasteful, and a bushing was pretty simple and quick to make with the right tools at hand with the Sherline lathe.

  

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1 comments

Having had the same problem on our original RepRap extruder I can definitely support the heat sink idea. I was able to stop this with a fan blowing on the PTFE insulator but I think that the heat sink will be even more effective. I have also read about using a tube brush to make sure that the transition from the PTFE to the barrel is as smooth as possible.