Extruding aluminium powder using a tiny railgun?

I was pondering methods that could be used as an alternative to Electron Beam Free Form Fabrication (EBF3), and I was wondering if a very small, low power railgun couldn't be used to create aluminum parts instead. I've read that you can make a mini-railgun using the flashes in disposable cameras, so I figured that it shouldn't be difficult to heat and accelerate small particles of aluminium to the point where they would fuse with other aluminium particles on impact. Each layer of an aluminium part would consist of hundreds or thousands of little "blasts" of a very small amount of aluminium powder at very close range.

Pros:

1. Should be able to build the mini-railgun using off-the-shelf components.
2. Doesn't require a vacuum chamber, radiation shielding or a powerful electron beam.
3. The tiny amount of aluminium being fired from a very close range would be relatively safe because the aluminium would have low mass and cool quickly. A Lexan box should be more than adequate protection.

Cons:

1. It would need a support material for complex parts.
2. You'd have to solve the problem of depositing the first layer. This may mean either using an initial sheet of aluminium and cutting it off later, or using a material to absorb the impact of the first pass of projected aluminium. (Support material?)
3. The railgun may wear out quickly. It would have to be very durable to survive the printing of a single part.

Any thoughts?

... aluminium is oxidizing instantly with oxygene, so you have to work in vakuum or inert gas ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

you are certainly thinking out of the box here - very interesting thought. I like it.

VDX Wrote:
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> ... aluminium is oxidizing instantly with oxygene,
> so you have to work in vakuum or inert gas ...

Would pure nitrogen gas react with aluminum under these conditions?

Hi Matthew,

AFAIK nitrogen is 'safe' - but all applications i know, welding and melting aluminium, use argon

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

not certain but i believe you will get a aluminum nitrate if you try to heat in nitrogen. aluminum is rather reactive with most things so inert gasses are a must.

... i've checked first: - aluminium nitrate is a combination with oxygene, so won't react in pure nitrogen atmosphere ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

sorry my last post was incomplete, i didnt mean aluminum nitrate specificly but a nitrogenation of your aluminum in general. all aluminum welding is done with either argon or helium. I tried to find any references to why nitrogen isnt ever used as a aluminum sheild gas but found none. The closest reference was that nitrogen in carbon steel welding will cause porosity, but all sources I could locate just say unsutable.

Depending on how your shield container was build would determine if argon or helium were better, if the container has a open top then argon, if open bottom then helium.

... the decision between Argon or Helium is mainly cost-dependant - Helium is much, much more expensive than Argon

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Any thoughts?

I'd do it backwards; lay down a bed of Aluminum powder and then sinter with an electron beam.
http://reprap.org/wiki/MetalicaRap

Or lasers
http://reprap.org/pipermail/reprap-dev/2010-December/002038.html

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-Sebastien, RepRap.org library gnome.

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