Extruder/Mendel

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Mendel Build Documentation



Mendel uses a thermoplast extruder based on RepRap's Thermoplast Extruder Version 2.0. The principle is exactly the same, but a redesign has condensed the RP parts into one component (click here for instructions on how to get hold of RepRapped parts). The non-RP parts remain the same, therefore please refer to the Thermoplast Extruder Version 2.0 documentation to assemble the non-RP components. The rest of this page will deal with the new assembly only.

BOM

Assembly qty: 1

Name Qty/assembly Total Qty Type
Thermal-barrier and nozzle 1 1 Assembly
pinch-wheel-bracket-NEMA17_604-bearing_1off.par 1 1 RP
m3-capx25.par 4 4 Fastener
m3-washer.par 4 4 Fastener
624-bearing.par 1 1 Bearing
m4-nylock.par 1 1 Fastener
m4-washer.par 5 5 Fastener
m4x16-cap.par 1 1 Fastener
m4x40-cap.par 2 2 Fastener
stepper-motor-nema17-fl42sth47-1684A-01.par 1 1 Motor

Thermal-barrier and nozzle

These are the only parts of RepRap that need to be machined.

Thermal-barrier.png

Here are the dimensions of the thermal barrier. It is made from 16mm diameter PTFE rod.

Start by facing off the ends. Then touch a centre drill on, and follow it right through with a 3.5 mm drill. Use a woodpecker cycle to clear the swarf.

Next mark 15 mm from the tip of a 5 mm drill with a fine felt-tipped pen (the tapping drill for M6), and drill to your mark.

Now mark 15 mm from the end of an M6 tap, turn off the power to your lathe, and put the tap in the tailstock. Turning the chuck by hand, cut the M6 thread to your mark.

The valleys cut in the end of the thermal barrier need to cover slightly less than the top 10mm of its length. They are just there to key into some glue, and so don't need to be very precise, nor do you need exactly two. I have made them perfectly well by putting the cylinder in the chuck of a Black and Decker drill and then just running a triangular file against it.



Brass-barrel.png

This is the barrel. It is made from M6-threaded brass rod (or an M6 brass screw with the head cut off).

Start by facing off the ends. Then touch a very small centre drill on. Drill the 0.5 mm hole for the nozzle about 3 mm deep. Go slowly and carefully, and withdraw the drill frequently to clear the swarf. An 0.5 mm drill is very fragile.

Next turn and clamp the cross-slide at 45o and turn the connical end. Take it far enough to get rid of the mark left by the centre drill and to take away a bit of the 0.5 mm hole. You will probably find that the 0.5 mm hole closes up - clear it by hand with the 0.5 mm drill held in a small hand chuck.

Holding both in your hands, offer up a 3.5 mm drill beside the brass. Get its pointed end about 2 mm from the tip of the cone you turned, and move it about so that it is as near the tip as possible while still leaving a bit of brass to hold the tip on. Mark where the other end of the brass comes with the felt-tipped pen, and once more drill to your mark. The 0.5 mm hole you made should meet up with the 3.5 mm hole, but you may again need to clear it using the 0.5 mm drill by hand.


RP parts

Extruder-printed-parts.png

Assembly

  1. Secure bearing using M4x16 cap, and glue nozzle assembly into pinch wheel bracket. Follow Thermoplast Extruder Version 2.0 documentation for gluing procedure. Note orientation of copper barrel tang.
  2. Loosely attach motor. Motor wires should run upwards. Set distance between motor shaft and bearing to 2.5 mm – use the round shank of a 2.5 mm drill bit poked down the filament hole as a spacer. Lock motor into position. Load M4x40 caps for ready for next step.

Extruder-assembly.png


Back to Mendel mechanical construction root.