Plasma cleaning- DIY HF HV source? - Page 1
Forum section: electronics / projects

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 08, 2018, 12:20:09 am
content: I've read that plasma cleaning can improve epoxy joint bonds. Is this as easy as running an HF HV arc over the surface? What's the simplest generator? Something based on a TV flyback coil, a Tesla coil, a neon transformer or something else? "Have wire, will wind."

author: MadTux
author_rank: Frequent Contributor
timestamp: November 08, 2018, 12:39:47 am
content: Used one at school some years ago.As far as I understood it, 2 plates inside a vacuum chamber at reduced pressure, so that plasma can form, HV-HF between these plates and the piece you want to clean, inbetween.It's basically reverse sputtering, gas ions that knock out impurities from the surface you want to clean, instead of depositing material.Oxygen plasma also reacts with these impurities. So you get a super grease/oil free surface that has a very little material sputtered away from the surface, ie roughness at microscopic level. So, ideal conditions for epoxy, if you can afford and fit into a vacuum chamber.

author: LaserSteve
author_rank: Super Contributor
timestamp: November 08, 2018, 01:21:34 am
content: Google "Oxygen /Argon Plasma Needle" that does not need the chamber, you can build a wand. I made one about five years ago for a Professor, 13 Kv pulsed DC at a few mA / few kilohertz.. With a series ballast resistor to protect the PSU.For the 9" diameter maybe 16 inch long plasma cleaning chambers at work we use 1-2 Torr of O2 or Ar and 13.56 Mhz RF at up to 1.5 Kw on a glass chamber with a large copper coil around it with a commercially made automatic matching/tuning coil box. A starting spark from a handheld tesla coil is some times needed, but the resonant coil usually provides its own ignition.Steve

author: coppercone2
author_rank: Super Contributor
timestamp: November 08, 2018, 01:41:44 am
content: for what?if you have metal, just heat it to 300-400C and it will literately burn any oils or anything on the surface. Steel will blue in this condition.You might ruin the temper and stuff, but for certain applications you can just use a torch even better if you sand it and then heat it in a inert atmosphere to the 400C temperature. Wrapping it in some aluminum foil or steel foil might be good enough. Then you have like 1 hour to work.Keep in mind though, some heavy oils will boil at like above 500C. If its in air obviously your gonna torch everything. Flame is like a plasma or is plasma.if you are actually using a stone I wonder if you can burn the stone first to clean it, burn the surface, then grind with the clean stone to get your epoxy scratched up surface thats oxide free.But for sensitive parts etc, you can find the youtube channel 'applied science' he does it to some microscope slides and stuff IIRC. Pretty sure its home made.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 08, 2018, 09:14:34 pm
content: This is for small metal and plastic parts that can't be heated too much. I found the handheld units like the Piezobrush, but they seem to be crazy expensive. I may try some experiments in a small vacuum chamber with just DC, a ballast resistor and operating in the corona region. If it looks effective, I'll see about building something portable for use in air. Thanks!

author: coppercone2
author_rank: Super Contributor
timestamp: November 08, 2018, 09:39:58 pm
content: He uses a tuning network for his

author: coppercone2
author_rank: Super Contributor
timestamp: November 08, 2018, 09:42:25 pm
content: I also had a thought, I wonder if epoxy would be stronger if you mixed it on fired ceramic or something plasma cleaned. I don't renember if the loctite syringe style mixers come packed in a medical style wrapping to make sure atmospheric vapor does not get into them. I wonder if the mechanics of the epoxy can make it so a film ends up building up ontop of the epoxy. Or if plasticizers can form a film on the plastic syringe mixer thing.I usually use medical cups that are in a big bag, I figure they are pretty clean, for jb-weld etc.How much does a Piezobrush cost? I never saw that before.LOL, I wonder if a 'violet wand' would work.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 09, 2018, 03:53:02 am
content: Drifting OT, I mix a lot of epoxy for critical joints. The medical cups are fine. My guess is even if they have some mold release, it doesn't come off or contaminate the epoxy. Always mix by weight on a good scale, never by volume. Stir with a stainless steel rod about five times more than you think is enough. There will still be films of unmixed epoxy on the walls and bottom of the cup. Pour or scrape the epoxy into a second cup and mix again. Degas it by vacuum for most any epoxy, or by centrifuge (only for unfilled epoxies). Figure out how to get your substrate clean. The best joints will be on etched surfaces, but the etchants necessary are usually things I don't want to use. I usually clean with Alconox and rinse with DI water using an ultrasonic cleaner. Wiping with most available alcohols will leave things worse than when you started. Not sure about other stuff. The water test is really important. If the water doesn't sheet, the surface isn't clean. The guy in the video doesn't really do it right. Here's an example of what plasma cleaning can really accomplish-FWIW, I've tested a lot of epoxies, including JB Weld. The stuff is really good for filling defects and sands and machines well, but you can do way better for adhesion. Industrial products like (Henkel) Hysol 0151 or the Epotek products like 353ND (needs high temperature cure) or 301 can do better. Filled epoxies can have improved mechanical properties, but may not "stick" any better. Whatever you use, keep it off your skin. People can become sensitized to epoxy components and if it happens, you might never be able to use it again, or even be in a room where it's being mixed.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 09, 2018, 03:59:52 am
content: I'll second the recommendation on care. I now break out in hives with any direct contact to a wide variety of epoxy resins. Fortunately my sensitivity hasn't reached the vapor level.I used to think gloves and other precautions were too much trouble. Wish I hadn't felt that way because now I have to take even more tedious precautions.

author: coppercone2
author_rank: Super Contributor
timestamp: November 09, 2018, 08:48:51 pm
content: Do you have any tips for epoxy storage?The main reason I use consumer brands is because they screw up in the containers.Superglue or methyl acrylate glues I never had a problem with, and I keep that in a jar with dessicant. All kinds of epoxy screwed up on me, including hysol brand. My MGchemicals silver epoxy is still good, even after a year. I am gonna be cursing hard when expensive silver shit goes bad though.I never thought to degas it in a vacuum chamber, I will try this.I use JB weld because it comes in a metal tube and I can pick it up in 5 minutes if I need it. I think it lasts longer then the loctite dual syringe ones from home depot etc. If I go with a product that expires (inconsistently) that I can't easily buy in person quick, its gonna end up pissing me off, and I can't justify it, because epoxy IMO is a good tool for weird unpredictable repair or assembly jobs that just come up randomly... and you can't really justify waiting or spending big money on those jobs IMO. If I need to use epoxy, I need it right there and now. Different if you run a production line or have a specific project in mind or have a big budget where you can afford to keep the good stuff on hand.MY mind would change if there was some known good way to store it that is not a bunch of hearsay. Or if they sold hysol brand in little metal toothpaste tubes so you can keep a few in stock.. those dual-syringe ones are just too big for low scale use.If you got one of the big ones, and transfered it into smaller evacuated containers, would you get the closed product shelf life?

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 10, 2018, 04:25:51 am
content: Storage can be a problem and I try to use the stuff before it goes "bad". If it crystallizes you can heat and stir both parts to get it back to good condition. That advice is right from some manufacturers. I don't like dual syringes at all. They can give inaccurate mix ratios and are subject to cross-contamination. I've purchased huge industrial ones and repackaged the stuff in plastic squeeze bottles, but it's a PITA and life wasn't that long. Nor am I a fan of 5-minute epoxy. It tends to be softer and not as strong, though the Loctite industrial one they sell in the big home stores is pretty good. If you can find regular cure "2-ton", that's decent. It's hard to find good consumer epoxy. Best bet is commercial stuff on Amazon. I've never used Araldite as it's uncommon here, but they seem to make some good stuff and it appears common everywhere but here.

author: LaserSteve
author_rank: Super Contributor
timestamp: November 10, 2018, 04:02:23 pm
content: Most Atmospheric plasmas are quite cold. We were using them on polymer nanofiber mats with no damage, just surface modification to enhance reactivity.Someplace there is a picture of a much younger LaserSteve holding his finger in the plasma (just Argon)With no ill effects while standing on a insulated mat.Steve

author: coppercone2
author_rank: Super Contributor
timestamp: November 10, 2018, 04:12:05 pm
content: what exactly happens to the surface because of plasma?Is it just thermal cleaning or is there mechanical deformation or some kind of chemical change (oxidation?)? I had it explained to me that in a RF plasma you can kinda think about it like a field basically causing the plasma molecules to physically beat/peen the surface kinda, based on the RF field frequency, in a harmonic motion, but with gas rather then a hammer.The possibility being to combine one of those wands with a gas tank or nitrogen generator possibly to increase activation (like a nitrogen generator from a airless soldering iron or medical oxygen gen or just welding tanks)?And conrad hoffman, have you ever degassed the re-stored epoxy under vacuum to see what would happen? I mean does it magically just fuck off once you break the manufacturers seal, or can it be resealed properly some how? If you can seal it into a bunch of small containers that are like 0.5cm x 3cm it would be great actually. I have a feeling I will just get a buncha covermyass bullshit from loctite. I am not making human organ replacements.Also for non-optical requirements, how does sand blasting perform compared to plasma? Especially if you cook the sand first to degrease it and run some through the sand blasting gun to clear out the internal buildup of crap, and you run the sandblasting gun from real clean dry air not a shady shop compressor?The plasma seems like a ultra-painintheass source unless you are dealing with something cosmetic or optical because it smells bad, high voltage, expensive, kinda can't tell if it is working without testing...Also, won't sandblasting generally be better because you cut into the surface physically, which is important for glues? I was always told to scuff stuff up anyway. I figure if you rough it up with like 80 grit sand paper, then sandblast that down so its not that jagged, you get a combination of high surface area and good dimensional fit (if its just sanded with low grit paper you get mountains your trying to glue).I am interested in this technology but I am trying to find out why it would be useful other then from stuff that really has to look super pretty and can't be masked with tape for some reason, because its just such a massive step up from what I am used to with glues.To use air correctly it seems like you would need to use a maybe a stainless tube connected to your regulator that you can decouple from the tank and also cook. The rubber hose seems like it would cause a problem. Since it's not being used for actual cleaning and just light surface work, you can make your own simple sand feeder you can also clean (see youtube for simple tutorials, you can make them with simple tools like files and drills, no need for complex gun systems).

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 10, 2018, 10:34:03 pm
content: One of my many holy grails is good epoxy bonding to 303 stainless steel. When I test, I always get adhesive failure- the glue stays on one part or the other and pulls away from the metal. I routinely sandblast (glass bead actually, with Trinmix #4) followed by water based cleaning. A water test on the stainless is never as good as I think it should be. What you want is cohesive failure, where the glue itself comes apart with some still adhering to the metal. I can do it with many other materials, including 400 series stainless, but not the 303. I'm guessing etching with a dichromate would improve it, but that's not stuff I want around, thus the interest in plasma. Unfortunately the application doesn't justify the several thousand dollars for the hand-held devices.All I can really say about the life issue is when you can't get it to recrystalize or the color changes or it doesn't cure to a hard glassy material with no films or stickiness, it's time to dump it. When in doubt test.

author: LaserSteve
author_rank: Super Contributor
timestamp: November 11, 2018, 01:18:11 am
content: Um, a surplus photocopier drum charging power supply, a ceramic ballast resistor, two tungsten welding rods, a bit of plastic, two microscope slides as plasma guides, plus welding grade gas tanks, with used regulators, were not that expensive. Plasma Pencils are trivial to build. I will admit a liter to two liters per minute of Argon can get expensive on a production floor.Steve

author: coppercone2
author_rank: Super Contributor
timestamp: November 11, 2018, 01:41:44 am
content: can you post plans?I seriously think it would be like a super popular project. Everyone hates gluing plastic shit.I wonder if I can just clean stuff with a plasma cutter ! I think it would be a bit much even on the lowest setting though.-type of electrodes (what doping? radioactive?)-what kinda plastic, teflon?-how to setup the plasma guides-anticipated pressure-V/I of PSU-What current limiting value (I guess this is standard for arc generation though)-angle of electrodes? Sharp or domed?-general layout of parts-any special inlet geometry for the gas etcand, is it a finicky bastard like a atomic hydrogen torch ?

author: coppercone2
author_rank: Super Contributor
timestamp: November 11, 2018, 03:22:39 pm
content: am I getting the idea right?What is the power supply? I see printers go from like 1-12kV.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 11, 2018, 03:29:57 pm
content: Heck, I've already got oxygen for the torch! I see commercial units that run at 13.56 MHz. Is there something magic about that frequency, or is there some unlicensed band there where the EMI won't get you sent to jail? If I use a chamber in the corona region, can I just use DC and a ballast resistor?

author: coppercone2
author_rank: Super Contributor
timestamp: November 11, 2018, 03:42:58 pm
content: with a plasma jet like that I have no idea. A metal plasma cutter works in the KHz I think.For a plasma chamber I heard (from someone) it had some effects on the momentum of the atoms but there is no real magic. 13.56 MHz and its multiples are basically used for this stuff. You get 27MHz and 40MHz too. They account for distortion and harmonics in the legislation.Are those 13.56MHz units powered by square waves?I am pretty sure a power supply for a copy machine is DC. A molecular hydrogen welding torch runs on 60Hz and it does something kinda like what I see the pictures of the plasma pencil on google do.Can you use this to clean wounds before applying a bandaid? Or before popping a zit? Wash your hands in the stuff?I am kinda thinking, once you strike the arc, you have a bunch of ionized stuff. When you have flow you start to get diffusion. I don't think it matters how you make the arc, just if the plasma will get to the outlet before it cools enough. Is dripping dye into a fluid stream a reasonable way to think about this?Is anyone else planning on substituting showers for plasma baths?I am imagining with DC you get a kinda steady arc that you adjust gas flow to diffuse a bit of the plasma to reach some kind of linear steady state wheras with AC you might be PWMing plasma doses into the argon stream and reigniting it, maybe, depending on the time constants. I think it might be actually some what possible to figure this out on paper using basic equations maybe.I might do this but I don't have any tig rods or copier HVPSU. I do have some spare teflon, argon and microscope plates. I do have MOT, 1.2kV lab supply and maybe some monitor transformers. Is tig rod really necessary at these power levels? Can't I use hardened steel like a sharpened drill rod or something?

author: coppercone2
author_rank: Super Contributor
timestamp: November 12, 2018, 05:03:29 pm
content: I managed to liberate a boiler ignition transformer. I dont know if its a autoformer or isolated but i can try it through a variacDoes the ignition transformer have a current limiting resistor built in since its made for arcs?

author: LaserSteve
author_rank: Super Contributor
timestamp: November 13, 2018, 02:51:36 pm
content: 17 milliseconds between pulses is too long to sustain "soft" plasma in air. I use pulsed DC at few Khz from the output of a short time constant voltage multipler in the photocopier charging psu. You reduce the gas flow to ignite the plasma in my design, then increase the pressure to extend the plasma out of the chamber. You need a thin Townsend like streamer, not an arc.Mots and furnace transformers have an air gap in their magnetic core to provide some crude current limiting by preventing saturation. A BIG TRANSFOMER like that is too powerful for small soft plasmas. And they will get you killed if you try them for this application at atmospheric pressure.Steve

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 13, 2018, 03:44:37 pm
content: If I want to try this with stuff off the bench (don't have any HV RF generators or flybacks hanging around), let's say I've got low current DC supplies up to maybe 1.5 KV or so. I've got power oscillators up to 20 kHz. I've got low power oscillators to 1 GHz. I've got wire and semis. I've got medium sized ferrite cores. I've got a PVC vacuum chamber with a rubber stopper and wires fed through. What would be the easiest thing to throw together? This is just way out of my wheelhouse.

author: coppercone2
author_rank: Super Contributor
timestamp: November 13, 2018, 05:19:37 pm
content: Yea furnance transfor.ers hurt like hell.It wont work if i find the right current limiting value? I dont like the idea of a pen either at such voltages, i was imagining more like a benchtop forge.I never looked at the frequency responce of a boiler transformer but from the sound of things it might not be good enough.Maybe a higher powered plasma would be useful for cleaning metal and ceramics and the softer one for plastics ?

author: coppercone2
author_rank: Super Contributor
timestamp: November 13, 2018, 05:28:13 pm
content: I freaking hate flybacks. I found one too but i dont want to deal with that crap.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 12, 2020, 07:15:41 pm
content: Updating an ancient thread, we did buy a Plasmaetch Plasma Wand, two actually. Way too expensive, but they do a nice job. Some of our parts are metal and you have to use a special nozzle, either that activates through glass, or one that shoots an argon/plasma jet. It's easy to wreck the unit if you pull too much current an overheat it. Don't ask how I know. A dramatic illustration of how well they can work is to take a piece of Teflon sheet and try to write on it with a Sharpie. Doesn't work. Then hit it with the Plasma Wand and try again- you'll be able to write on it. I doubt you could bond to it, but I've been pretty successful at getting epoxy to adhere to Delrin and similar things. The guts of the unit are here-https://www.tdk-electronics.tdk.com/en/373562/tech-library/articles/applications-cases/applications-cases/cold-plasma-from-a-single-component/1109546

author: coppercone2
author_rank: Super Contributor
timestamp: November 13, 2020, 12:18:45 am
content: And I upgraded to a glue gun with mix nozzles and Loctite epoxy products + a minifridge*you get screwed by the price of the different ratio plungers, given they are simple plastic parts... but sometimes the glue is a bit hard to squeeze out so you actually need a high quality strong plastic for the gun, particularly if you are impatient to fully warm the tubes up after cold storageI don't think you can get similar performance from degassed mixes as you can with the mixing tube. I gave up on vaccuming the mixed glue because if its too viscous it seems worse after the vacuum.Also, the acrylic epoxies are very nice, and smell nice (like wintergreen or something), and have glass beads in them to ensure proper joint thickness on compression. These have a much better adhesion to plastic also. They are weird though, it makes me think of working with a liquid spider web.you can say my glue budget is dried out at this point with all the new acquisitions over this yearThere is a table some where that tells you the viscosity in CPS vs the type of mixing/degas that works.. when it gets too thick you need to mix it under vacuum or in a mix nozzle for it to be any good. It seems the vacuum pot method is only good for stuff up to the viscosity of maple syrup.Do you know about proper methods of laying the glue out? Like with a glue comb or such? I was thinking about 3d printing a glue comb but I am not sure if the effect just looks good or if there was any thought to how the comb was designed.I glued a ton of stuff this year and honestly I can't stand the smell of normal epoxy anymore.. the acrylic is a nice changeAnd for polyethylene I am quite satisfied with primer + loctite prism glue, I want to say its strong enough that the only appeal for the plasma cleaning is for chemically resistant joints that you get with epoxy. If its simple mechanical chassis stuff, you can get by with the super glue, so long the joint areas are big enough, for hobby electronics. I might try a piece on teflon if I can find a flat bit. Good enough for a inductor coil bracket insulator I think.

author: SilverSolder
author_rank: Super Contributor
timestamp: November 13, 2020, 03:33:20 am
content: If you don't like the smell of epoxy, try the urethanes... pure evil!

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 13, 2020, 03:40:07 am
content: Not a clue about glue combs. We use EFD units and sometimes robotics to place small dot patterns. If you're getting any kind of good results with polyethylene, you're doing great.https://www.nordson.com/en/divisions/efd/products/fluid-dispensing-systems

author: SilverSolder
author_rank: Super Contributor
timestamp: November 13, 2020, 03:55:55 am
content: I spoke with a 3M rep yesterday, they have some products that claims to do the low surface energy plastics - I think it is DP8005 and DP8010 - without surface prep.I have a project going on where I need to glue some polypropylene panels - hopefully, this will work! (will find out this w/e)

author: coppercone2
author_rank: Super Contributor
timestamp: November 13, 2020, 08:33:57 am
content: yea I have both 8805 and 8810. Those are the glass bead ones that self adjust thickness with pressureKeep in mind 1:10 mix ratio. You need the gun with the 10:1 and the mixing nozzle is different for them. They come in cool colors so you can see the bead line well (teal, blue). So the common glues are 1:1, 1:2 and 1:10I have one tube of polyurathane 2 part glue that I will be using to glue a rubber guard on the bottom of a garage door eventually. I think its the best glue for the job but I am not looking forward to using it. For the loctite prism glue and medical primer, I glued AA cases to plexiglass with sanding and priming, and the body material of the battery case (the black plastic ones) started to rip before the rubberized prism glue when I attempted to crack it off. Not sure if it would take an impact sideways loaded with batteries, but I assume its doing pretty good if the ribbing is ripping before the bond is failing. When I tried it without the activator, it just left a superglue mold behind. You work it like nail polish, the coating is super thin.Those battery packs just have metal that is melted into the PE plastic, so there is not good clearance if you need to attach it to metal, so you can glue it to a plexiglass sheet and screw it to something.