3D Printer Extruder Notes

Intro

An extruder is the print head for a 3d printer. It acts like a hot glue gun, pushing plastic filament into a hot end, which melts it and lets it out through a small hole.

There are already many open source designs for extruders. The Open Source Ecology project wants to develop one that is as simple as possible to build and can be attached to the CNC machine in place of a cutting tool.

I've done some research into what's out there and here are some relevant existing designs.

Plastruder MK5

The MakerBot Plastruder MK5 has excellent documentation on its assembly and usage, is built using cut out flat parts, so it doesn't need an existing 3d printer to build, and has tons of experience and testing put into its design. On the downside, it may be a little more complicated than it needs to be. Some potential features for simplification are:

• Using straight cuts instead of curved cuts for improved rigidity and speed and easy of construction, especially by hand.
• Using fewer different types of parts. Its simpler to source parts, build, and document if is uses 10 of one kind of screw instead of 5 of one kind and 5 of a different kind.
• Using round spacers instead of bolts to mount the hot end to the plate in the middle, similar to how the plate is mounted to the feeder. They'd need to be made out of something that can handle more heat and then we might want to replace the existing plastic spacers to use the same part.

Stepstruder MK7

The MakerBot Stepstruder MK7 is a compact and simple design for smaller filament than the MK5. Like the MK5 is has excellent documentation and lots of experience went into its design. It requires 2 printed parts.

Adrian's Geared Extruder

Adrian's Geared Extruder is the standard extruder for the RepRap Mendel.

Wade's Geared Extruder

Wade's Geared Extruder seems to be one of the simplest out there. It's got only 4 printed parts, including gears.

RepRap Universal Mini Extruder

The RepRap Universal Mini Extruder is a compact extruder which is somewhat similar to the MK7. It seems to have more simple inputs, for example you cut slots into a metal rod to make the filament feeder, rather than ordering a pre-made steel part to do that.

Huxley Seedling - Wade's Extruder

This is a design based on Wade's Geared Extruder which uses layers of flat material, like the MK5, instead of printed parts.

http://reprap.org/wiki/Huxley_Seedling#Wades_Extruder, http://reprap.org/mediawiki/images/b/b8/Wades_Extruder.pdf

Erik's Bowden Extruder

A bowden extruder has the filament drive mounted to a fixed surface instead of the print head, and feeds the filament through a flexible tube to the print head where it is melted.

http://reprap.org/wiki/Erik%27s_Bowden_Extruder

QU-BD Extruder

QU-BD Extruder. This is apparently based on the Makerbot MK8.

Ultimaker Extruder

A simple extruder design that uses a bowden tube. This page only has some of the build instructions, although what's there looks very clear and simple.

http://wiki.ultimaker.com/Ultimaker_rev.1_assembly:_Extrusion_head

Hot End Designs

http://reprap.org/wiki/Geared_extruder_nozzle

http://reprap.org/wiki/Huxley_seedling_hot_end

http://reprap.org/wiki/DIY_Direct_hot_end

http://reprap.org/wiki/J_Head_Nozzle

Existing OSE Work

Various people have been working on a RepRap at Factor E Farm - http://opensourceecology.org/wiki/RepRap_Build