Grain micro powder printer

Powder and inkjet printing
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dragonator
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Grain micro powder printer

Post by dragonator »

It has been a while since I posted new stuff. I have been (and still am) busy with other projects. One of them is finally finished however. This was Grain, the micro powder printer.
Grain overview 1.jpg
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Grain overview 2.jpg
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Grain overview 3.jpg
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Grain overview 4.jpg
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Grain overview 5.jpg
Grain overview 5.jpg (202.44 KiB) Viewed 2734 times
When the Z400 was working, and Oasis was also operational, I was stuck with a problem. I have no powder printing recipes. I have the machines, but not the materials to print with. This left me with a problem that I had to do a lot of experimentation on 2 relatively large printers. I had several options.
  1. Test powders in a manual setup.
  2. Accept that I had to test with large batches on Oasis.
  3. Modify Oasis with smaller pistons
  4. Design a micro printer
My reasoning at the time was that:
  1. Would not yield consistent results
  2. Was undesirable given the amounts used
  3. Oasis still has a normal HP45 head and it would require quite a bit of work
  4. Would also require a lot of work, but would also allow me to test a few new things
I decided to design a micro printer I called Grain. It was to have the following specs:
  • Ultra small print size. 13x40x30mm
  • Small footprint
  • CISS or small volume printhead (I went with CISS)
  • Test my new DMA head
  • Test virtual velocity
  • Test single cable control
The small size would allow me to test tiny batches of powder. The CISS head I made myself by glueing a tube to the ink inlet port on the HP45. The CISS printhead has no real ink capacity and would allow me to quickly change binders. The DMA is something I already tested and wanted to have in a real printer. It prints using DMA, which allows for faster prints. I don't really use the speed on this printer, but it is nice to give it a proper test. The virtual velocity allows me to print without an encoder, and is interesting for other uses of the HP45 controller. It uses an optical endstop to sense a flag somewhere in the path. Once this endstop triggers, the printhead will reset to a given to a position, and then move at a constant velocity. All other functions will just keep working. I can now toggle the head between encoder mode an virtual mode. The old encoder connector can also now be used to mount switches and signals to trigger the virtual velocity. Below a photo of the flag.
Grain flag 1.jpg
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One last thing I wanted to try was single cable control. Oasis has 2 USB connections, 1 for the motion, and 1 for the inkjet. I wanted to see if I could remove the one for motion and attach it to the inkjet. However, I need to know exactly when the motion is done moving. I had used GRBL for Oasis because it was available, and wanted to try a RAMPS on grain. However, all possible firmware will not tell me when it is at it's destination. It is always too soon or too early. I went back to GRBL and went back to 2 cable operation. I could in theory attach GRBL to the HP45 standalone controller, but given that GRBL was already a very hacky solution, I want to thing a while and maybe try something better.

Grain is currently ready to print. The CISS head is a story for another time, but it works surprisingly well. The controller with firmware will not be share right now since it is not yet ready.

Now for the important question, was Grain the right choice? With the benefit of hindsight: No. I was supposed to be finished 3 months ago. Not all of this is the fault of grain, but quite a bit is. The new controller took too long, the virtual velocity took weeks to code in, the whole Oasis controller software was never meant for this and was hacked so it would work with Grain. In the time it took, I could have easily made new pistons and a printhead for Oasis. Now that I do finally have it I can finally start experimenting with powders. I will start a new thread for that once I have started.

(PS: I discovered that Oasis cannot actually print in the negative direction. If you are encountering troubles with this, message me and I will share the fix)
(PPS: I should really start a Github for this project, keeping the updates central and easy to find is currently a bit of a disaster)
smeric
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Re: Grain micro powder printer

Post by smeric »

is it using color cartridge ?
selimmeriçMSc Electric & Electronic Eng.
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dragonator
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Re: Grain micro powder printer

Post by dragonator »

It is an ordinary HP45 head, but I can easily fill it with any type of ink I want. I preformed the tests with yellow ink.
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Re: Grain micro powder printer

Post by dragonator »

I have started printing with the micro printer. I have not yet started with serious materials and mixes, but I have had some tries to get a feeling for the printer.

First I tried construction plaster. It spread horribly and leaves a rough surface. It also is completely unbound by the binder. Even 300% density did nothing at all. I then tried wallpaper paste powder. It spread with a lot of resistance but it did actually spread. I do have underfeed. It still did not solidify, but I still have to try at higher densities. The powder did swell when binder was applied, which is an unpleasant property. The picture attached is wallpaper paste.
IMG_20200515_200330s.jpg
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I will try to get the powders I need to make proper experiments. These are maltodextrine, proper plaster (perhaps dental plaster), and hopefully PVA powder. I also need to give the printer a proper permanent place. I currently lack desk space and have to move it constantly. More news if I have either failed at dozens of recipes, or if I stumbled on something workable.
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