Empiric 3000 3DP printer

Powder and inkjet printing
Posts: 29
Joined: Mon Aug 26, 2019 9:13 pm

Re: Empiric 3000 3DP printer

Post by rofl »

It is a ribbon mixer.
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I designed it and 3D printed the hole rotor. I pushed through it a rod of calibrated steel to make it more rigid (it worked as axis) and installed 2RS bearings on both sides.
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Its purpose was to make small batches of powder mixtures. I also made V mixer, which is even more crazy, but I am not sure if I ever going to use it all. This ribbon might do the job for a while. I also learned that I should also consider some sifting device later, but I postponed this one for a while.

I started working with locally sourced plaster (with the base of plaster of paris). I bought three and two of those were quite expensive. One worked really well out-of-the-box with water, but it was hard to justify the price. Second, although expensive, was not working with sprayed water at all. Third one was fair enough called FormX UltraCal 30. It hardened some what with raw water and price was OK for 5kg. I chose this one as first raw material for further improvement.
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I decided to give it a try to improve the flow behavior of powder with hydrophilic fumed silica. As a binder, although I tried powdered sugar, I learned that PVA powder (160 mesh) works way better. Also green parts (or droplets of hardened powder to be honest) with PVA proved to be more rigid and tough when bind with water (compared to powdered sugar). Regarding water, I added SDS to reduce surface tension.
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Exact amounts of all components are still WIP, but I will share these a bit later after some more testing (manual spraying and manual deposition of water over the powder mixture). That is the work done before actual printing.
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Re: Empiric 3000 3DP printer

Post by dragonator »

I was not familiar with ribbon mixers. Neat to know.

Dental plaster supposedly works well without additional binders with water and alcohol. I have also heard Maltodextrine works well instead of sugar. I have not tested any of these myself. I discovered that I really did not enjoy material studies.

Where do you source the PVA powder. Most Dutch suppliers only really sell it solid or dissolved. I have been meaning to try wood with PVA.
Posts: 29
Joined: Mon Aug 26, 2019 9:13 pm

Re: Empiric 3000 3DP printer

Post by rofl »

Well, anything that starts with dental seems to be pricey. I do not wish to go beyond 10-15€/kg to be honest, yet. Considering that my goal is not plaster, but metals, I just wish to use plaster to understand process parameters as it is less expensive than pricey AISI 316 powder.

I tried maltodextrine, but its particle size is quite large. At the least the one I managed to source in local food store. It is powder however, but particle size is quite large. To be honest, sugar worked even better for me.

Regarding particle size, I would like to go below 100um per particle. Preferred size is around 50um in order to have around 2 particles per layer (i.e. for 100um layer two particles of 50um in ideal scenario).

I sourced my PVA powder from China, Alibaba. However, the smallest I managed to get was 160 mesh. I tried to ball mill it, but also without significant success. I stayed with 160 mesh though. The price of PVA I bough was quite expensive (PVA itself was free as a sample, but because I bought small amount shipping was pricey from China), but did not pay attention to price now, I simply wanted to have some for tests and later I might buy more of it for larger amounts. So far I have several kilos of PVA powder 160mesh. If you could tell me how much you need for your wood tests, I would be able share a bit.

Anyway, with PVA it seems quite good. I am tuning steppers today and some other minor stuff with the printer and I hope to try one already mixed batch of plaster. Binder would be deionized water with a pinch of SDS.

P.S. I have received new HP45 driver yesterday. I do not know, when I have time to solder that all together and test with RPI, but let's hope it will happen in a month or two.
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