IR reflective polymer available as fine powder?

I'm working on a powderbed thermal fusing inkjet printer (similar to the HP MultiJet Fusion), and was curious if anyone know of a cheaply available thermoplastic with these properties:

* IR reflective or transmissive
* Amorphous temperature of approx 150C-190C
* Not poisonous when at amorphous temperature
* Can be wetted by either alcohol or water (ie, not hydrophobic)
* Available in bulk as a coarse (< 0.5mm grain size) to fine (< 0.1mm) powder

The theory of operation of BrundleFab is that I inkjet an IR absorptive pigment onto a powder, then I run a high intensity halogen light over the powder to (hopefully) selectively fuse the darkened area.

I'm thinking powdered acrylic (plexiglass), as that meets these qualities, I believe.

Any good sources for powdered acrylic in bulk?

Am I forgetting some other excellent material?

... a good material for tesing and lost cast moulding is icing sugar ...

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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]

As you may already be able to tell form the linked wiki page, I am using sugar as a powder medium currently - it's great as a cheap powder, but terrible for 'ready-to-use' objects.

One issue I have with sugar right now is correctly handling the fact that it expands in the Z direction when heated, and the next repowder operation scapes the freshly fused layer off.

I'm planning a sequence of experiments using increased cooling times, cooling fans, changing up the fusing sequence (currently it is during the repowder phase), etc.

Hopefully I'll nail this down.

... this 'Z-expanding' should be an issue with the heated surface, as the molten track contracts and forms blobs or round traces ... this could be similar with other powders too.

So maybe you can try with smaller focus diameter and lesser powers?

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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]

I am not using laser based spot heating, but a halogen lamp to do area based heating.

The pigmented powder absorbs the IR radiation more quickly, and fuses before the unpigmented powder.

That being said - yes, I have observed that the heating phase is critical, and overheating leads to the pooling behavior.

its all a matter of dialing in the temperature and duration

... ah, OK reread the initial post again - you're going the areal sintering route ... I've confused it with SLS, what I'm more focussed on

Are you aware of SIS (Selective Inhibition Sintering) with IR-absorbing powders and salt solution as ink?

Here you'll only print thin lines, which won't fuse when melting the topmost layer, forming separation lines between fused areas ...

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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 yes - SIS basically is printing the "mold", right?

I can use my sugar printer in that way also, to make positive wax (or chocolate).

Although my interest lies in direct object creation at the moment, using my process as a way to generate molds for other materials is a good thing for me to keep in mind.

Thanks for the information!

... not only molds - you can print fully functional parts with SIS - it's the same methodics as the old LOM 3D-printing, where you have stacked/laminated sheets of paper or plastic and cut contour lines and an overlayed 'separation hash-grid' over the outer areas.

When finished the complete working room, you'll get a solid block with a hash-grid on top ... when breaking/separating the hash, you'll free the embedded objects.

With LOM laminated paper objects resembled the texture of wood with horizontal brown (the cut contours) and white (the transparent glue and not burnt paper surfaces, shining through).

With full fused SIS objects this should be different - they should look like made with SLS -- but finer, not so 'sandy' surface ... and more articulated horizontal slices ...

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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]

Back to the topic at hand -

Anyone know of a good source for acrylic powder, in bulk?