Laser-Jet 3D Printing Proof-of-Concept.
I wanted to see whether embossing powder would adhere to itself to create a 3D form. I accomplished this by applying a layer of glue over a previously embossed layer. The results are encouraging.
@Nick_Parker , this format should be more readable. Let me know if you have any thoughts!
The goal is to lay each layer of powder via the same mechanism that lays toner in a laser-jet printer - static electricity. This will obviate the need for the glue layer and will increase the accuracy of the powder particles.
There are some current concerns that I discovered in this experiment. The main concern is that the Paper Source Embossing Powder melted entirely too much, and lost almost all of its structural integrity upon meeting it’s plasticity-point. This causes two undesirable symptoms: the top layer will tend to melt into spaces left in a layer below it, and the top layer will flow laterally. Both of these symptoms contribute to the mounded shape as seen in the last picture. Possible solutions include more closely controlling the temperature to which each topmost layer is heated, and/or choosing an embossing powder that retains its shape better while only melting slightly at its outer edges to provide adequate structure.
How does the material get released from the static roller?
If the roller doesn’t prevent this, I would try much smaller particle sizes.
Just as in a laser-jet printer, there are several rollers that each play a critical role in the deposition. Mainly, there is the organic photoconductor drum, which has a voltage of about 600V applied to it evenly across its surface. Then, a laser shines on the surface of the drum which creates what is called a ‘latent’ image on the surface of the drum. The surface of the drum is then supplied with toner, but the toner only sticks to where the laser shone. Separately, in a laser jet printer, the paper is applied a static voltage. Next, the drum rolls over the paper, and the toner jumps from the drum to the paper due to the stronger static charge on the paper than on the drum. Heat and pressure are then applied to the paper to fuse the toner into the fibers of the paper. This heat explains why papers exiting a copy machine or laser jet printer are nice and warm.
Now, extrapolate this process to 3D.
Instead of toner, we will use something akin to embossing powder (in reality, they are actually very similar). Instead of paper, we will apply the powder on top of the layers of molted powder that have come before them. Thus, each new layer builds the 3D object in the Z axis. To directly answer your question, the powder is released from the static roller because the powder is attracted to the stronger charge of the paper (or in this case, the stronger charge of the surface of the melted materials).
Alright that all makes sense. I’d definitely try smaller particles.
How are you heating the material?
For the experiment, I heated it with the heat gun shown in the first photo. But in practice, there would be a heating roller or a corona wire. Both of which rely on resistive heating. The heat gun blows hot air.
Smaller particles would theoretically give better resolution in the same way that a smaller diameter filament can give better resolution in extrude-style 3D printers (like RepRap or Makerbot) if the servomotors have corresponding resolution. But the tradeoff comes in the need for more layers to achieve the same height, and increased processing power to calculate the laser bursts onto the drum in the higher resolution.
Note that toner particles (like the ones in your laser jet printer) are about 10 microns. They are anywhere from 5 to 10x smaller in diameter than the embossing powder particles. Thus, to achieve the same printed height, 5 to 10 more layers would need to be laid, increasing the print time 5 to 10 fold.
There are tradeoffs in everything 