Dan Maloney
Q: What type of electron gun is it out of interest, from what i understand there are different types, is it thermionic ?
A: Yes, there are different types, shapes, filaments, for the electron gun. I´m going to detail this in the project page :)
Using the e-beam to keep the whole working volume at an elevated temperature is common practice in commercial e-beam powder bed systems.
@RichardCollins Do underestimate people. You ca roll your own oil diffusion pump.
For vacuum class feedthroughs, I heard about active brazes that can braze ceramics to metals (typically titanium is added for oxide ceramics, manganese(?) for graphite). For sealing of the minute cracks, silanols could be used to deposit silicate within in a sol-gel way.
Q: Even with your baffle, oil contamination of the vacuum chamber is inevitable. Are you concerned that oil contamination will effect how smoothly the powder move? Can you heat the powder to drive off all of the oil?
A: Good question George. As soon I get the 0.1mm diameter spot Im going to perform the sintering tests and report the results back to you
I think not needing an aneling oven is a small advantage compared to not needing a high powered laser.
Another thought. Thermal camera to watch the powder surface, and feedback to the beam control to deliver just enough energy.
@Al Williams As I recall, one of the problems with a beam onto a complex metal object, is that when it accumulates charge the field calculations get complicated. And there are xrays when you start ramping up the power. Your current is limited by the electron source and that is a materials problem. If you use ions, they are heavier and have a much smaller wavelength for precision, and heavier more momentum and energy per particle. The mass spectrometer guys and accelerator guys have some pretty good methods.
Q: If you don't have another source you can get high vacuum electrical feedthroughs from the magnetron tube in discarded microwave ovens. I have dozens of magnetron tubes that I have been saving for the feedthroughs if you want some
A: Yes please!. I really appreciate it. We can talk later. Many thanks George for your help!
annealing
Q: Thought. Can the gun be defocused, resp. the beam spot area regulated? Then it could dramatically lower the time necessary for the rastering over the area. We need to deliver x joules to mm2, so a fat beam with higher current vs thin beam with lower current, switchable/adjustable during process, could give us both higher speed and high details... am I right?
A: You can defocus the electron beam. This is an advantage over laser. You can control the power and the beam diameter. So, you can defocus to heat the powder, and then you can focus again to sintering the powder
@RichardCollins Oh, that's interesting. A big problem with e-beams is that the melt pool gives of gases that cause scattering, so the feature resolution is limited by this scattering.
I'm thinking that wouldn't be as problematic for heavier particle beams.
I'm not an EE but along the lines of accessible technology, you can also get 6000VDC power supplies from old microwave ovens. The last stage is a voltage doubler maybe you could double is again. I don't know how smooth it is and if you can vary it. I know they are typically rated at 1000W of microwave power but I don't know if that means that the power supply puts out all of that, more or less.
What do you expect to be the biggest roadblocks and most expensive parts of the system from where you stand?
could the powder be locally preheated, drive out the gasses, and THEN melted?
Q: (apologies if I missed the answer): How are you planning on tightening the beam? Magnetic focus or a pinhole or something else?
A: It uses electromagnetic focus and deflection system. Uses coils to move and focus the beam
Have you estimated or worked out the cost for parts? Would it not be faster and cheaper to use traditional welding together of parts, molds or simply farm out the work? Any developing country that can do vacuum 3D sintering is going to be able to do those other things well, and there are lots of jobs empty. I think electron beams are a good investment as a technology, but if you can do that well, there are groups who want it all over the world. If you get developing countries to have these skills and tools, are they going to stay home or leave to find jobs?
Q: Using the e-beam to keep the whole working volume at an elevated temperature is common practice in commercial e-beam powder bed systems.
A: Yes. You can defocus the beam to heat the working area, and then focus again to start the sintering process
Focus and precision beam control, at much lower power and much higher precision, is handy for scanning electron microscopy. Could you leverage the similarities?
Q: For vacuum class feedthroughs, I heard about active brazes that can braze ceramics to metals (typically titanium is added for oxide ceramics, manganese(?) for graphite). For sealing of the minute cracks, silanols could be used to deposit silicate within in a sol-gel way.
A: Yes. There are commercially available high voltage feed feedthroughs, but they are expensive. I tried using spark gap from airplane too, but they break at high voltage. So I'm using a homemade solution. Cheap and good for low income applications :)
I'm curious, is the scanning setup a raster scan like a regular TV tube (at least back in the day) or is it more like a vector tube, like the CRTs that were in the original "Asteroids" arcade games?
Q: I think not needing an aneling oven is a small advantage compared to not needing a high powered laser
A: An aneling oven needs too much power. For domestic application I think is difficult to have an aneling oven.
Q: Another thought. Thermal camera to watch the powder surface, and feedback to the beam control to deliver just enough energy.
A: Yes. That is a good solution to control the thermal input.
I'm far from an expert in this field , But 100w Electron beam seems a bit small for the task. Is this number targeted after any other similar sized product ?
Thermal cameras don't really work well on powder bed systems.
A big factor in choosing the components and materials in your vacuum chamber is maximum temperature that they have to endure. I saw that you polished your chamber. Are you planning on having the ability to bake it out?
Q: I'm not an EE but along the lines of accessible technology, you can also get 6000VDC power supplies from old microwave ovens. The last stage is a voltage doubler maybe you could double is again. I don't know how smooth it is and if you can vary it. I know they are typically rated at 1000W of microwave power but I don't know if that means that the power supply puts out all of that, more or less
A: I think that source of high voltage is not very stable. You need DC high voltage as stable as you can. The only way is using high frequency AC and convert it to high voltage DC using a voltage multiplier
Using ferrite core flybacks
Some modern microwave ovens use high-frequency SMPS kind of a power supply, instead of the laminated-steel transformer.
Maybe the new inverter microwave ovens would work. They have high frequency supplies and DC multipliers.
Q: I'm far from an expert in this field , But 100w Electron beam seems a bit small for the task. Is this number targeted after any other similar sized product ?
A: That depends on the working speed. 100W in a 0.1mm diameter spot is enough for sintering the powder :)
Jinks. buy mew a coke
Buy me a coke.
I need to move over to a computer.
Q: A big factor in choosing the components and materials in your vacuum chamber is maximum temperature that they have to endure. I saw that you polished your chamber. Are you planning on having the ability to bake it out?
A: Yes, the vacuum chamber inner walls are polished. The working area is exposed too high temperatures. So you need to take into account cooling aspects in the design. I will publish this later in the project page
Q: Some modern microwave ovens use high-frequency SMPS kind of a power supply, instead of the laminated-steel transformer.
A: You are right about this. Maybe is a good and cheap solution
Hello, reading through the comments, there was a discussion on oil and soluitions. I could not see what the actual problem is?
Hola @Agustin Cruz !
Sorry I couldn't make it earlier, are you staying a bit more ?
Did you also try "dumber" solutions such as the following one?
https://hackaday.com/2013/11/07/3d-printing-with-metal-at-home/
I'd really like to make this approach work...
The parts you might make will go into some markets or into your own products. Any country that wants to make precision metal parts either casts or mills or welds them, even by hand. If you don't clarify your market and how you will serve it, a general method won't help. But if you are simply training the new generations of kids from developing countries, then probably you should teach them how to start businesses, write sensor and control algorithms, find material properties, find partners and parts. You are at the beginning. If you lay out the things we talked about here and get that overview available to all the people you want to help, you might make a difference. EVERY country in the world has some people working on these kinds of technologies and they are NOT working together. Thanks for you very interesting work. I am not trying to discourage you, but to encourage you to look at the whole world.
Q: What do you expect to be the biggest roadblocks and most expensive parts of the system from where you stand?
A: The main roadblock is the financial support. So I opened the project to the community inside a crowdfunding model. The design, tests, updates, will be shared so I can receive some support and continue working 100% in this project
Re markets... what about the components? The power supply, the electron gun, the vacuum gauge system... whatever vacuum/electron-related system it is, whether printing, furnace, welding, microscopy, or special electron tubes (TWTs, klystrons, whatevertrons...), you have at least some of the key components ready.
@KMICKELSON The oil diffusion pump will coat everything in your system with a thin layer of oil. Clean surfaces are important when welding. Especially when welding with little or no flux.
Q: could the powder be locally preheated, drive out the gasses, and THEN melted?
A: Yes. This is a common practice i think. To insert heating elements inside the powder tank
Well, we've been peppering Agustin with questions for an hour now, and he's been a real champ about it. We'll let him get back to work now, but not without a big "Thank you" for the great chat. Personally, I can't wait to see developments with his project -- sounds like a great technical challenge that could potentially open up a huge new area for the home-gamers. Thanks, Agustin!
Thank you Agustin... good luck!
Thank you all!
Thanks!
Yes. Thanks!
Idea re fluxing. Some alloys are self-fluxing, eg. the copper-phosphorus braze. Can something like that be leveraged for powder melting?
Thanks too!
Thanks a lot Agustin! Awesome project I can't wait to see where it leads
Thank you Agustin. Top Shelf project you have on the go.
Q: Focus and precision beam control, at much lower power and much higher precision, is handy for scanning electron microscopy. Could you leverage the similarities?
A: Yes. If you install a backscattering detector you can make a electron microscope, and use it as a camera. This is a feature in some commercial models
Thanks a lot! Look forward to following where it goes in future!
Also, random thought. Diffusion brazing. Silver-coated copper grains. Locally heat, a layer of copper-silver eutectic forms, joins the grain. Then put the sintered thing into furnace, let it wait, let silver diffuse from the joints into the bulk, have a (porous) copper object.
A huge thank you @Agustin Cruz for this incredible chat. Best of luck
The issue is not "Do capitalists or the state own the means of production. The goal is getting the means of production into the hands of the people.
I'll be posting a transcript soon, in case anyone wants to refer back.
Many thanks Dan. I think there a lot of questions
@Dan Maloney Thank you for doing this, it makes a difference.
And good answers
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