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

Thermoplast Extruder 2.0

http://reprap.org/wiki/ThermoplastExtruder_2_0

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/TechZone_Tip_Assembly - a simple hot end with a wood insulator. doesn't look like it can be mounted to a wade's extruder without some modification.

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

http://reprap.org/wiki/ThermoplastExtruder_2_0

Bamboo hot end

http://wiki.arcol.hu/arcol-hu-hot-end-v4-assembly, http://reprap.org/wiki/Arcol.hu_Hot-End_Version_4

http://www.reprap.org/wiki/Buckrap_Hot_End_Bow - a simple hot end for a bowden extruder

Existing OSE Work

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

Dan's Design Notes

Hot end:

• start with 36mm m6 brass heater barrel.
• screw 0.5mm nozzle onto one end.
• screw 2 m6 nuts on most of the way to the nozzle. leave a small gap around each nut.
• put thermistor between nut and nozzle and tighten nut and nozzle gently until thermistor stays.
• wrap about 1' of nichrome wire around the barrel and thermistor in the gap between the nut and nozzle. it will help hold the thermistor in place. leave 2 inches of each end of the nichrome wire sticking out.
• use the 2nd nut to clamp the nichrome wire ends between the 2 nuts to hold it in place. there should still be about 2 inches sticking out.
• strip the ends of the nichrome and use metal crimps to attach to thick wire.
• cut 1" off of a 5/8" dowel.
• drill 3/16" hole through it the long way.
• screw the end of the barrel into the wood a bit until it's really tight.
• fit the dowel into hole in the bottom of the feeder and screw in 2 wood screws to hold it (TODO size)

Test results:

• ~7.5v seemed good
• main problem is that plastic kept coming out after i stopped pushing it in