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Thermal binding of sucrose - any prior art?

Posted by Ezrec 
Thermal binding of sucrose - any prior art?
August 06, 2015 12:02PM
For my BrundleFab sugar based powerbed printer, I am working on a layering mechanism where I lay down black ink on the sugar, then use a thermal pass (halogen lamp from a laser printer) to (attempt to) bind the sugar that is colored, without melting the white sugar.

Has anyone seen any prior art on this? The closest I can find is the HP Multi-Jet Fusion process, but this appears to be just curing the binder (and not using sugar), and is very sparse on details.

The ChefJet 3D uses an inkjet process, but I believe they are using a binder in the powder/ink, but not a thermal pass to melt the printed portion of the layer.

Does anyone have experience with these devices?

My hope is that if this works, I should be able to get some relatively strong (for sugar) parts out of it.

(Note that I do not intend to sell this printer, as the HP Multi-Jet Fusion probably has a pile of patents surrounding it. It's only for my own interest).
Re: Thermal binding of sucrose - any prior art?
August 16, 2015 09:57AM
Update: I have the pigment-based selective fusion process working, it's VERY tricky with granulated sugar:

* The grain size is so big that pooling and other surface tension issues make the layer very uneven
* Due to the above, the next recoat pass has a tendency to disturb the layer

I'm going to start working with finer grained sugar media, I'll update this once I get something working.
Re: Thermal binding of sucrose - any prior art?
August 18, 2015 08:19PM
Update:

(see latest videos and materials experiments on http://reprap.org/wiki/BrundleFab )

Powder Size:

Curiously, a finer powder (ground granulated sugar) requires more energy to get to the fusion temperature, not less.

It appears that the fine powder is more highly reflective to IR, and requires more ink to achieve the same level of saturation as granulated.

This make sense, in retrospect, since the fine powder has a much higher surface area, and therefore requires much more ink to reach pigment saturation of the layer.

Fusion Technique:

With a single slow pass of the halogen lamp fuser, I had difficulty with pooling, and unpigmented areas becoming sintered. The overall temperature of the powder was difficult to control.

I did some rough experiments with multiple (faster) passes of the fuser, and I have much more consistent results. The sugar bed temperature raises to the just below the critical point, then the last pass fuses the inked area, leaving the uninked area as powder.

However, my scavenged halogen lamp holder (ABS plastic from a laser printer) is unable to tolerate the multi-pass technique - lots of burned plastic smell,

I'll need to alter my lamp holder design for higher temperatures, and add a IR thermal sensor to the layer head to monitor bed temperature.
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