2011-07-04

extruder design

Being unsatisfied with the filament drive of the Thing-o-Matic
(way too little pulling force),
I'm in the early stages of designing my own extruder.
Design-intent:
  • geared down stepper motor
  • spring-loaded lever to adjust the pressure
  • mount for a rotary-encoder that meassures the filament being actually pulled in
  • integrated compartment for a sponge to clean the filament
  • use herringbone-gears
  • mounting holes for a fan for the stepper motor
  • low center of gravity (reduced stress in transport and backlash)
  • allow ToM and RepMan hot-ende and allow both extruder mounts (I want to design this only once for both my printers)
  • 3 point mouting (use 3 contact points to mount the extruder to a Thing-O-Matic z-stage as opposed to the flawed arc-like 2-point design of the default MK6-steptruder. Doesn't matter on a Repman.)

Originally I wanted to use 2 drive-grears to grip and pull the filament from both sides instead of clamping it between a drive-gear and a 608-bearing but I found that this would require a more complicated gear because the only stationary point on the lever is it's axis and that is not the axis of the intended second drive gear.
So that would require 2 more gears in a very small space.

Don't hold your breath. This will take me a while to get right but I'm working on it.




Kommentare:

Triffid Hunter hat gesagt…

looks like greg's accessable wade's v3. any significant differences between your design and his?

Marcus Wolschon hat gesagt…

Where to find it?
Do you mean this one?
http://www.thingiverse.com/thing:8252

What about:
* no encoder to detect failures (a MAJOR point for me to get unattended prints of dozens of parts in a row)
* no mount for BfB and Makerbot hot-ends (I require both)
* no herringbone-gears
* thicker axis on the lever
* lower center of gravity
* no sponge for dust-removal
* no fan mounting
* he does not define the BitsFromBytes hotend-mounting that I require to mount this to the RepMan 3.1
* He does not define what toolhead-mounting it has. It surely does not have RepMan and ThingOMatic at the same tine.
I guess it mounts to a RepRap of Mendel or Huxles. Certainly not a MiniMendel. Maybe a Darwin.
The photo shows it printed on a Mendel but that does not have anything to say about what printer it is intended for.
* He uses SCAD (BETA, not a single stable release, certainly not finished) while I'm using a CAD program and plan to export it to a range of industry standard file formats that can be used in assemblies of other CAD designs.

I like the open design with the accessible drive-bolt axis.