Sidestepping my filament feed problem

I still can’t get the bruthead to feed the beginning of a new length of filament directly into the groovemount. It runs fine past the gearhead, and down through the bottom of the printed plastic piece, but it never quite lines up with the hole in the groovemount. The hole in the printed piece is larger than the one in the groovemount, and the filament catches on the edge of the hole.

[UPDATE: There is an easier way. Simply removing the idler wheel assembly (held on by the four bolts with springs around them) lets me feed the filament into the groovemount by hand, around the gear head. Then re-connect the idler-wheel.]

My solution is not one I would want to be doing frequently, but I’ll only have to do it when starting a new roll of filament, so I can tolerate it. So here is how to start a new reel of filament, if your bruthead won’t do it automatically.

By the way, before doing this I built myself a filament reel that I bolted to the ceiling with a quick release mechanism, a swivel so that twists in the cable get untwisted automatically, and a brake mechanism inspired by car drum-brake actuators that provides adjustable friction to stop the whole lot unspooling on my head. I’m pleased it works, since its all made from meccano and foamcore.

Loading new filament into a MakerGear BrutHead stepper extruder and hot-end

Cut off old filament

If you have any filament still going into the top of the bruthead, cut it off near the top of the brut-head. I didn’t, because I kept printing til the old filament ran out. I have half a 20mm calibration cube as my first printed object…

Remove the idler-wheel assembly

Mark the top of the extruder idler-wheel assembly (the one with the 4 long bolts with springs going into it) with an arrow pointing toward the filament, so you can put it back on the right way round later. Unbolt the assembly, and set it aside.

Disconnect extruder and thermistor

Unplug the wire connectors from the extruder motor and hot-end thermistor, so you don’t break them.

Remove extruder assembly from x-carriage

Unbolt the extruder/motor/hot-end from the x-carriage. Carefully lift it up and away from the x-carriage.

Take the groovemount and its plywood spacer off the bottom of the bruthead. If you still have filament passing the gear there may be a little friction, but with the idler wheel removed it should all move freely.

Place the groovemount and plywood spacer on the x-carriage, but don’t try to bolt them down (because the nuts are on the bruthead). Rest the bruthead on the printing bed out of the way.

Removing old filament from groovemount

This step only applies if you have filament already in the hot-end that you need to remove, not if this is the first time you’ve used this nozzle.

Reconnect the wiring to the hot-end nozzle and the hot-end thermistor. Put them and their plywood spacer back in their usual printing position on the x-stage.

Plug in the USB cable and the ATX supply, and switch on.

Fire up Pronterface, tell it to connect. Set the hot-end temperature to the right number for your filament (185 celsius for my PLA). Monitor the temperature.

When it reaches your target figure (185 for me) hold the hot-end’s plywood spacer down on the x-carriage with one hand and use a pair of pliers to gently pull the remains of the old filament out the top of the groovemount.

Once you’ve got it out, use Pronterface to set the hot-end temp back to off. Watch the temperature drop back down to ambient, so you won’t permanently scar your fingers with burns in the next stage.

Threading the new filament (finally!)

This is the whole point of the exercise. Thread the new filament down through the hole in the top of the bruthead, past the extruder gear and out through the hole in the bottom. Line it up with the groovemount, and push it into the hole in the centre.

Be gentle, and don’t force it further than it wants to go – there will be a plug of old filament in the bottom of the groovemount that you can’t move when its cold. Also remember the filament is 1.75mm, and the nozzle is only 0.35mm so you can’t force it through. Don’t try.

Carefully reconnect groovemount and bruthead

With the filament in the hole in the top of the groovemount, gently refit the groovemount and bruthead back together, keeping the end of the filament in place. The filament in the bruthead will happily slide past the driven gear since it isn’t being compressed by the idler wheel.

Final reassembly

Bolt the bruthead/extruder back onto the x-carriage. Bolt the idler-wheel assembly back onto the side of the bruthead, making sure the arrow from step 2 points at the filament.

Extruding the new filament

Reconnect the hot-end nozzle and hot-end thermistor. Use Pronterface to heat the nozzle back up to temperature and then extrude say 50mm to be sure you’ve got past the possible air gap between the old and new filament.

Set the temp back to off – you don’t want to leave PLA cooking at extrusion temperatures unless you are printing, because the heat can ride further up the groovemount and do bad things.

My second printed object was a completed 20mm calibration cube.

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2 Responses to Sidestepping my filament feed problem

  1. Pingback: My Mendel Prusa 3D printer is brazenly extruding plastic | Brazen Artifice

  2. Pingback: Building a MakerGear Stepper Plastruder for a Mendel Prusa | Brazen Artifice

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