wood as fabbing material

Hi all,

... yesterday i found in my basement some samples of injection-moulds made with 'fluid wood' from a project-development out of 1997 - the company started as spin-off from the project can be found here: [www.tecnaro.de]

The method used for the injection-mould isn't so easy adaptable for us, as they use very high pressures and temperatures.

But this let me think about mixing wood-dust with some epoxy for room-temp fabbing or mixing with some sorts of shugar-base for heated (melting) extruding with the reprap-head.

I think the amount of wood-dust could be something between 60% and 90% (look at the 94% sand and 6% epoxy for virtual stone) dependant of the desired viscosity.

This could be a very interesting cheap and 'green' material

Viktor

Something else you may want to check out is balsa wood filler. Here is the stuff I have used for model airplanes for years, it is water soluble and dries quickly. After drying it can be cut and sanded like real wood.

While doing a google search for the stuff above, I found this, which may also be helpful... [www.airfieldmodels.com]

Hope this helps,

Jeremy

... when finding some more time, i will test with wood-dust, talkum, and waterglass - this could be an interesting mix for fast hardening, light but very stiff material with low shrinkage.

In particular you can use any powder or dust (or mixtures) you have at hand - the 'magic' lies in the fluid base: epoxy, dextrose/shugar, waterglass or others ...

Viktor

Slightly off your topic, sorry viktor.

Injection molding.

I have been thinking about this and can;t help but feel that micro injection molding may be doable with a slightly modified extruder.

We would need to add on a heated shot/piston assembly but the existing extruder with a 1mm orifice would be fine to charge the shot/piston assembly with molten plastic and drive it back.

Injection is initiated through a gate into the die then in the usual way by driving the piston forwards and discharging the accumulated shot into the die. (depending on the pressure needed, Aqualung compressed air might be sufficient to drive the piston)

We would be using the filament as feed rather than granule feed. much simpler and far less bulky and less chance of gas entrainment.

Thought for what they are worth.

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

Hi Andy,

... for micro-injection-moulding you need very high pressures - common systems drives much more then 1000bar!

An alternative is 'hot-embossing': - here you have your micro-moulds in hard-alloy or ceramic, cover with a slice of a thermoplast, heat it up and put it in a press where the melted compressed thermoplast fills the mould.

After cooling down you can strip the residues and extract the micro-parts ...

Viktor

Hmmm

Hot embosing sounds remarkably like a way to press out 6mm roller chain components for making our own drive chains.

The side plates need to be around 1.5 to 2mm thick and are just out of our current printable range of accuracy. The rollers I am still thinking about.

1000 Bar, easily within the range of hydraulic pressing, out of the range of direct Aqualung cylinder pressure (232 Bar). However using something like the technology used in a Haskel pump it should be possible to run 1000 Bar hydraulics from Aqualung Cylinder Pressures. In fact if you get the dimensions correct sub Aqualung pressures would be usable.

As the volumes are relatively low for micro injection you should get a few cycles out of one fill.

15 Litre Aqualung new tested runs out at approx

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Necessity hopefully becomes the absentee parent of successfully invented children.

In fact come to think of it.

There is no need for a hydraulic component just use the pressure step up of big cylinder to small to do direct low pressure gas to high pressure injection.

100 Bar to 1000 Bar is only a * 10 step up. ie surface area difference of 1:10 10 being the compressed air side.

for standard compressor air assume 10 Bar tops. this is a * 100 step up and may need to be acheived as * 10 followed by * 10 as a 1:100 difference in cylinder diameters is getting a touch large.

Fewer parts and cheaper to run.

Only really attainable because the actual volume of plastic to be injected is actually fairly small.

Beyond a certain shot size this gets to be prohibitive.

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.

I realize this is not a fresh topic, but I have a question.

If you have the "liquid wood" (Arboform?) in filament form, then is it necessary to do "injection molding"? Or could you just do normal RepRap deposition (Fused Filament Fabrication)?

Or does the "liquid wood" cool too slowly to be practical for this?

-Jesse

Hi Jesse,

the Arboform process use fine wood-dust and steam at high temperatures and pressures, to convert the wood dust in a fluid material usable for injection moulding.

When it cools down and sets, its no more thermoplastic

For a thermoplastic material you need a thermoplastic base, which you can fill with any other dust too, so wood dust won't be of special use ... except for a 'geen'/recycling approach ...

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

Viktor,
Thanks for the explanation.
The terse pages and the videos on Tecnaro suggested it remained a thermoplastic at about twice the vikat temperature of polylactic acid. But if it loses its thermoplastic nature as it sets, that does make it less desirable.
-Jesse

Hi Jesse,

... wait, i was wrong!

When i was in contact with them between 1997 an 1999 they were starting with 'steam-wood', what was not practicable as thermoplast - now they have some more materials with thermoplastic behaviour, so i have to update ...

But i can't find the temperature and pressure settings - it seems, that the materials are sutable for common injection moulding, but we have to check if it can be used with the RepRap-extruder ...

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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]

... in the meantime i had a talk with one of the guys at Tecnaro.

The material is something special - lignin behaves normally as duroplastic, but above 150 centigrades and with high pressures (800 to 1000 bars) it went fluid and can be used for injection molding (so i wasn't complete wrong ).

He thinks its nothing for our extruders, but we may test it.

They sell granulat and some of their customers make monofilaments from the granulat, so maybe i can get some probes.

Another interesting point: they can give me some powder, what could be a real good candidate for laser-sintering, as its much darker than normal wood-dust and will melt/fuse to solid ... and it stays bio-degradable

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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]

Ah! So with their newer formulations there are possibilities.

Good to know.

Looking forward to learning enough to get more involved.

Thanks again, for your prompt responses, and for going above and beyond to update your first answer with new information.

-Jesse