what to expect from home made ferrite cores? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: September 01, 2018, 12:52:45 am
content: As someone that will one day soon own a nice vacuum/inert gas capable kiln, capable of being poorly insulated and overpowered (to allow for temp profiles unlike a economy kiln designed for $$$) and ball mill,What do you think the outcome of some kind of home made inductor cores will be? Has anyone made their own?Other then the annoying ball milling and sieving steps, it seems like a fairly strait forward process so long you get pure materials to begin with. Since you can epoxy coat them, I don't think the complicated diamond grinding process for final shape is too important (papers seem to agree), so you can probably do a half decent job by hand with a die grinder without the need for complicated grinding machines.The calcination process seems like the most difficult step that would require experimentation.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: September 01, 2018, 03:51:18 am
content: Can't believe it would be worth the effort. I think you also need a press to get the density up, and some might be sintered in a hydrogen or other atmosphere, but not sure. That said, there are all sorts of different formulations with different properties, so you're bound to get something that could be used for some application.

author: coppercone2
author_rank: Super Contributor
timestamp: September 01, 2018, 04:54:40 am
content: I really want to try it. I could do hydrogen into the furnace too, any atmosphere will work, the hydrogen just should be burned off so it does not build up some where and cause an explosion. I can make a solenoid bank that pipes different gases into the furnace during the cycles.Are you sure it needs to be pressed? That is irritating because it requires high strength molds and makes me not want to do it. Anything with 'real' molds makes it completely unachievable for me.I do like chemistry so its not as much of a chore as you think, but I don't like freaking molds. I am not making a god damn high pressure mold or dealing with greasy hydrualic bullshit. I thought maybe I could make something out of clay with some fixtures.If you need a press then the idea is scrapped completely. I refuse to do forming operations that don't involve a vice and a hammer.God dammit, it looks like I would need to make pressed ferrite cylinders and grind them to shape. I am not doing that much material removal. fucking goddamn press.shit needs at least 10 ton/inch. you need machine toolsMan all these cool things you can almost do end up requiring some freaking spray or press process that makes it completely fucking unachievable without understanding some boring hard to do crap like die/nozzle making. Same with foil caps, they spray the metal on the ends (but MAYBE you can get around that like I wrote in my other thread).one little step from 1 car garage to 50,000+ in machine tools

author: JS
author_rank: Frequent Contributor
timestamp: September 01, 2018, 05:21:05 am
content: Tooling, it's always about tooling!JS

author: coppercone2
author_rank: Super Contributor
timestamp: September 01, 2018, 10:26:40 am
content: Some literature just says the spray drying step "allows the powder to flow". Might this not be a mass manufacturing step (since you can justify a crushing die in a large factory)?So you go from 1um particles to 75um (weak) balls which are crushed and can flow easily into the mold from a powder hopper.Doesnt the crushing just revert it back to the 1um powder??Can you not instead just use the 1um powder, deal with its unruley nature that does not allow it to flow well, and perhaps add some % of much finer nanopowder (if necessary) to fill in the dead space between the 1um powder?Does anyone understand these steps? What the fuck is this spray drying crushing shit achieving??? It seems like your undoing your last step for no other reason then to allow a powder hopper to function. I know really fine powder cakes like a mother fucker (like pyrotechnic aluminum) so it would just not work unless you do it by hand. It would also result in a major dust problem if you used it in bulk pouring it into molds.Am I missing something unrelated to mass production? The ceramic does not deform, I figure light pressure and vibration should cake up 1um particles completely. Unless the point is to make them abrade eachother somewhat into nanopowders (which can seived out and added later if this is why). Some people calcinate then spraydry some people spray dry and then calcinate. Don't know why.This might be possible after all. Unlike a factory I can afford to fuck around with delicate things that disintirgate if you sneeze on them.Does anyone knowledgeable in powder metallurgy know why they do binding and pressing?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 01, 2018, 10:44:29 am
content: Keep going! Maybe one day you can make heads for reel to reel tape machines?

author: coppercone2
author_rank: Super Contributor
timestamp: September 01, 2018, 10:51:22 am
content: Yea I saw a paper that mentioned the type of ferrite you need for magnetic heads lol.I just wanna figure out if there is some kind of uneconomical process (because this will be completely insane from a economical standpoint anyway) to avoid the seemingly useless spray drying and pressing steps.grrMixing and GranulationIt has been notedthat for many operations including ferrite manufacture, mixing withoutgranulation causes unacceptable property variations. This problem can be attributed to dry powders having lowinter-particle attraction,hence easy to shift positionsleading to de-mixing. There can be substantial de-mixing in subsequent handlingprior toand during calcination.For example, the showering action of a rotary calciner tends to segregateparticles.Granulation modifies ingredientinteraction, limiting or freezing particle mobility, thereby stabilizing microscopic composition.Therefore, granulationimmediately following mixingis preferred, and ideally as a cycle extension in the same processing equipment.Furthermore, since granules tend to flow more readilythan powders, theyhelp tominimizethe possibility ofcalcinermishap where process upset canturn powders into a fused mass, which becomes difficult to handle.*******but then maybe you can granulate, calcify/partially sinter and remill?it might be good enough if the well mixed stuff is kinda fused a bitFrom what I understand if you just use strait up nanopowder you can get cracks

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: September 01, 2018, 11:05:59 am
content: I can't believe a press would stop you considering everything else you need. Buy a cheap lathe (how the heck does anybody get through life without a small lathe?) and make some simple cup and plunger dies. Either put them in a vise to compress or hit them with a hammer. Heck, the vise on my mill is rated at 60,000 psi. Be glad you'r not doing piezoelectrics that need high density. They put those in a rubber bag and then into a hydraulic system under huge pressure to compress the powder. Here's a small manual version-http://mmrc.caltech.edu/Optical%20Furnace/Manuals/Hydrostatic%20Press.pdf

author: coppercone2
author_rank: Super Contributor
timestamp: September 01, 2018, 11:16:32 am
content: does the pressing increase density when the particles are already like 1um? whats the point? Can't vibration and light presusre do it, why do you need 10 tons per square inch on tiny nondeformable material?are you destroying little towers of jagged particles that allow for density voids (that form by chance)? whats going on in there on a microscopic level

author: coppercone2
author_rank: Super Contributor
timestamp: September 01, 2018, 04:03:26 pm
content: I ask because when I imagine metal powder being pressed hard, it deforms somewhat, so it becomes structurally sound. I am having a hard time imagining metal oxides doing this because they are super brittle. Not trying to be condescending towards presses. I can't fathom what is going on. I can't see plasticity, so what is the mechanism of action?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 01, 2018, 06:53:50 pm
content: Ceramic particles exhibit ductile deformation. Just not to very much degree. If nothing else, given enough pressure, the particles will crumble, forming a dense pack held together with intermolecular (van der Waals) forces.A binder is usually used, which can probably be found at pottery supply houses.https://digitalfire.com/4sight/education/binders_for_ceramic_bodies_345.htmlDefinitely don't use hydrogen. It /will/ explode. Simple as that. Even mature industries prefer to avoid using it, where they can.Also because hydrogen probably ruins it. MnZn ferrite is the ferric (Fe III) state, hydrogen would reduce it to Fe(II) or less. Mn can be oxidized to Mn(III) as well, which is probably undesirable too. I would guess if air doesn't give reliable results, a neutral atmosphere (CO2 or N2) is probably best.Tim

author: coppercone2
author_rank: Super Contributor
timestamp: September 01, 2018, 07:09:54 pm
content: you can use hydrogen I have seen how its used industrially the absolute main thing is that you need to burn it off and ensure like a triple safety on burning it away. It would use alot of hydrogen though (I don't know if pressurizing a hydrogen 'pipe bomb' for a reaction to occur at high temperatures is a good idea, so you need to waste it in flow. And it might diffuse like crazy out of a hot vessel. And superheated hydrogen would probably blow the fuck up if you had a breach), so you need to keep it at atmospheric pressure with minimal flow.You also want laminar flow at the chimney exhaust to ensure that air does not get sucked downwards and mixed with it to blow up the chiminy, and maybe a flash arrestor.If you put the thing out doors you can't really have a problem so long its away from anywhere that wind can possibly accumulate it in any ingnitable quantity, the flow should be low enough to just control a decent burn on the furnace exhaust. Like if you have it near a structure its possibly feasible that hydrogen can accumulate along a roof top overhang and ignite and cause structure fire or something like that. Obviously indoors it can explode or ignite near the ceiling. If you put in a field the failure modes are tank rupture (this is worse with acetylene welding, the tanks are the same) if the regulator or plumbing fails, so you get a fire plume, or the pilot flame goes out and you have a bunch of light hydrogen going into the air. Obviously having a chimeny to keep any fire away from the ground would help alot with saftey. You also want some kind of flame indicator since its kinda hard to see it .It's diffusion into air is the best of all gasses, and its the lightest gas, so you don't really have a chance of some kind of long 'hydrogen snakes' carrying fire into weird areas like with heavy gases (gasoline vapor). I imagine if the wind, air temp and humidity is just right heavier gasses like gasoline vapor could get into strange areas and propagate in funny ways, like end up in a nearby ditch, drain pipe, under the floor, etc in explosive quantities.Not that I want to use it, maybe for mu-metal.Do you know how much density change there is in the compaction process of ferrite ? I know EVERYTHING is a bit ductile but I just see it as inconsequential. If you are just crushing it to make it finer then why not add some finer powder? I am kinda imagining vibration and light pressure aligning it correctly. I know with magnets they magnetize during crushing, I assume this is because the material fractures somewhat and you get particles that are free from other forces that might be mechanically aligned by the magnetic field.I mean based on that, I assume crushing it will be at least a little better , but maybe its of little consequence compared to the benefits that can be achived by making a really well engineered core for your device, the step may be a nuance for electrical reasons but followed strictly because its extremely good for high volume production.I want to know for sure. If its like a 5% difference in quality it does not make sense to go through all the trouble.