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Improved Huxley design I am working on an improved Huxley design.  This is slower than I'd like, owing to lack of time, but it's coming together.

A few key points:

The first version will have a moving Y platform, like Mendel.  But MakerBot have taken Ed Sells' idea of building on a conveyor belt and made it work, so I think replacing the Y motion with a belt will follow soon after.

Labels: Huxley, OpenSCAD, slide bearings

# posted by Adrian Bowyer @ 12:20 AM 13 comments 
Conductive pastes take 453

As ever, I'm constantly on the look out for nice conducting materials. I recently stumbled across a special powdered Nickel. What’s particularly interesting about it is that it is dendritic i.e. the particles are spiky rather than spherical. Essentially this means that when mixed with a polymer, the metal particles are more likely to touch each other so it therefore gives a much lower resistance.

Apparently this stuff is typically used making conductive paints, so its readily available. I managed to get some filamentary powder thats about 2.35um in cross section and 15um long . In small quantities this costs about £95/kg

A colleague and I crudely made a thin film that measures 100x100x1mm out of this powder mixed with liquid latex in a 1:1 ratio in terms of weight. The paste seemed sufficiently viscous that we could extrude it with a paste extruder. We embedded 9 electrodes in the film so that we could get repeatable readings. The total resistance between opposite electrodes came in at 0.8ohms, which is about a 9cm length spanning the film. I guess this is sufficiently low to be useful for a lot of low current applications. Labels: nickel, paste, reprappable electronics

# posted by Rhys Jones @ 2:28 PM 8 comments 
Filling in with the fillings

I've recently been experimenting with the loading of various fibres into CAPA and PLA. This started out as simple strengthening for the 3mm PLA that I sell, but the addition of 20 micron x 1mm nickel fibres makes it conductive. Dunno how useful this will be yet but it certainly allows RFI shields to be printed.

Then I hit on a brainwave: short polyacrylonitrile fibres. There are normally used to reinforce synthetic rubber. But they have another use: The feedstock for carbon fibre.

My trick is to mix polyacrylonitrile and similar materials in with PLA or CAPA. This is then turned into filament, which in turn is printed into an object on a RepRap - this tends to align the fibres.

The object is then encased in a ceramic and heated to the vapourisation point of the PLA or CAPA. You then have a ceramic mould stuffed with oriented polyacrylonitrile. Introduce an inert atmosphere and raise the temperature and you have a mould full of carbon fibre. This can be surface-activated in the usual ways, or coated with vapour deposition before being vacuum-encased in epoxy to form a complex, 3D carbon fibre composite object.

Yes, I am looking for sponsorship :)


Labels: capa, carbon, composite, epoxy, fiber, fibre, pla, reprap

# posted by Vik Olliver @ 9:13 PM 5 comments Evolving the Prusa Mendel: Part 2

Two weeks ago, Rob posted about some of the awesome stuff we've been doing with the Hacklab Reprap, a Prusa fork. I thought it might be worth while to bring everyone up to speed on what has happened since.

 # posted by Christopher Olah @ 6:30 PM 0 comments 
RepRap MicroExtruder I have started to design a MicroExtruder for 1.8mm filament.  So far I have just got the non-reprapped parts, shown above.

As you can see, it is about the size of the two end joints of my index finger.

It is a miniaturised version of my standard extruder here, which was based on ideas from Nophead and others, with bits from me.

From the top there is the filament (green - thanks Vik!)  then a length of 8mm diameter PTFE.  This screws into the brass nozzle with an M6 thread.  There is then a PEEK disc with two 2mm holes either side.  Those will take two M2-threaded rods.  The tension in these will resist the extrude pressure.

The brass nozzle is threaded M4, and screws into a small brass heater block.  This takes the normal RepRap thermistor for temperature measurement, and is heated by an 8.2 ohm metal-film resistor rated up to 235 oC, which should give 16 watts at 12 volts.

The filament hole down the PTFE and brass is 2mm in diameter.

So far it is untested - watch this space...

Labels: extruders, miniaturisation

# posted by Adrian Bowyer @ 10:33 PM 16 comments 
The Emerging Economy of Home Manufacturing

Hod Lipson and Melba Kurman were asked by the White House to write a report on the emerging phenomenon of home manufacturing.  It has recently been published and - as you would expect - it makes interesting reading.  You can access it here:


Labels: government report, Home manufacturing

# posted by Adrian Bowyer @ 1:33 PM 3 comments 
Evolving the Prusa Mendel: Part 1

Chris Olah and I have been developing a fork of the Prusa Mendel at Hacklab.to over the past couple months with 3 major goals:
1) get larger build volumes from a smaller printer footprint [we don't have much room at hacklab]
2) reduce the printed and non-printed part counts
3) increase the configurability of the Prusa Mendel
Today we are able to show the first parts of the Hacklab RepRap - a simpler, smaller and more configurable Prusa Mendel. I'll leave the in-depth discussion to Chris but heres a couple pics to wet your appetite: Full details in Chris's post..

Labels: Mendel

# posted by D1plo1d @ 5:49 AM 0 comments 
Belt drivn extruder

It occurred to me recently, after building two mendels, and printing way too much (including one of those mendels), that the weakest harware point in my Mendel was the gearing on my extruder/s.

They always seem to have problems.
I have problems with:
*printing the teeth nicely/accurately,
* getting the teeth to mesh,
* keeping them meshed over time,
* teeth wearing out or getting "chewed off"

and the resulting printing issues these cause!

So, I thought "I don't have issues with the XYZ axes anymore, so why not use the same principle/s on the "E" axis.?

Result: A belt driven "adrians" extruder.

I took a random "big" cog for a belt, and a semi-random "small" one ( ie matching), and put them on one of my extruder/s. It's awesome! I haven't "skipped" , or chewed a tooth or anything in ages!. It was a little fiddly sewing the belt together ( with a needle and thread ), but that's just because I'm too cheap to buy one the right size.

and a youtube link to it printing:

Labels: belt driven extruder

# posted by Buzz @ 3:41 AM 7 comments