Pulse Arc Welder Circuit - Page 1
Forum section: electronics / beginners

author: diyfella
author_rank: Newbie
timestamp: May 04, 2025, 10:44:56 am
content: I'm building a diy pulse arc welder (the kind of welder jewelry makers use) but i'm having trouble getting it to weld, instead i'm getting a very laud bang and a crater in the steel sheet. I have an Arduino Due that reads a 40v low current across the electrode and the workpiece, it activates the solenoid that pulls the electrode away from the workpiece and as the voltage drops below a certain threshold, it fires a bank a 5 2200uf 50v capacitors charged at 40v.any insights would be appreciated.thanks in advance.

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2025, 11:43:09 am
content: I thought a critical part of these welders is that the electrode does not touch the surface and has a mechanism that makes it work like tig on a timerI thought they need argon too.I thought its not a short circuit machine but it makes the arc as it lift ups the electrode (lift start). Essentially a tig welder on a solenoid, so it would need the mechanical part, the gas, tungsten electrode, and a HF arc circuit. I don't even know if it uses capshttps://www.sunstonewelders.com/collections/pulse-arc-welders-tigChina might have a bullshit version going of some kind that does something else. I don't know how you can half ass what is basically a robot tig welderI am guessing maybe for inert metals you can skip the gas if you are welding gold or something non reactive. if you watch the videos of jewlery welders you will notice the electrode retracts after you trigger itYou see, when you hear the word 'arc' it means the arc is doing something. Its a resistor and it gets hot. If you have no resistance you need a incredible current to get power dissipation, but the arc is like a resistor. Then you can weld something at a comparatively lower current, making it possible to ground it. P=I2R.The 50 volts you have, its not doing shit in a short circuit situation. The voltage on a resistance welder is like very low, maybe 1V (the voltage across the weld, if you were to measure the work piece some how). You need voltage if there is a arc because its a resistor, if there is an arc there no contact (electrode separated).If you try to spot weld with a high voltage, you just get a arc in the air before the electrode makes contact... but I believe the priciples of the machine is to have the weld form as the electrode is retracting. If you have arc before the electrode makes contact with the intent of the weld occurring after contact, IMO it just fouls up the contact surface, maybe a slight controlled arc could help with contact wetting if things are dirty prior to spot welding, but this arc would probobly should be wimpy

author: diyfella
author_rank: Newbie
timestamp: May 04, 2025, 12:03:16 pm
content: I got most of what i know from this guy who built the same thing.http://pulsearcwelder.blogspot.com/2012/08/page-1-pulse-arc-welder.html

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2025, 06:17:54 pm
content: you are missing like 50 details for this to be helpableit looks like the blog you found has the right idea for how this type of welder might be designed, but its a complicated one and your details are non existent

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: May 04, 2025, 07:31:22 pm
content: Hello diyfella,Country = Antartica Do you sell jewelry to penguins ?If you manage to control the welding current,there should be no crater.Try to swap the polarity.Having a look atFritzs' power PCB, I see 7 power mosfets in //.Sure that with 8800 µF capacitors, you store enough energy for arc welding ?Because the stored energy @ 40 VDC is only...7 JHowever, the reference design you mentionned speaks about 200 Ws = 200 JI would rather see a ballpark between 0.5 and 1 Farad at 20-25 VDC.1 F @ 20 VDC = 200 J.Very high currentMOSFETsare becomming affordable.On the second picture, the display shows 'VSET = 150' Is that 150 V ?Maybe the capacitance is not that high but instead, the voltage is.A balanced solution could be 8 x22 000 µF 50 Vin //, charged to 48 VDC that stores 202 J.

author: SteveThackery
author_rank: Super Contributor
timestamp: May 04, 2025, 08:53:15 pm
content: Got a question about this. A normal Tig welder creates a continuous arc and requires you to feed material into the weld. I've only played with one jeweller's welder, and that was just an electrode and the part to be built up. So, is it the polarity that determines which way the metal gets deposited?Presumably the electrode and the part are both made of the same material, because you want to deposit steel on steel parts, silver on silver parts, etc. Is this correct?

author: coppercone2
author_rank: Super Contributor
timestamp: May 04, 2025, 10:02:52 pm
content: I thought it used a tungsten electrode and just melted stuff together without a fillerYou don't NEED filler if the joint is tight and there is not much penetrationAs I understand it, if you tried to tig with random metals to deposit from the tip, you would have a giant problem of the metals work functionand you would need to re-grind it every time.same with laser, you can do it with or without a filler.What you are proposing would be some variation of a MIG welder, like metal spray or something. If you have a wire thats a electrode, I believe there are three different 'operation regiemes' for metal transfer that can be achieved with different technology. Dip in pool of molten metal (short circuit), drips or spray. Normal hand tig I think you ideally want 'drips' but there will be some 'pool feeds' too (its not short circuit since its isolated from the arc, its nearly pure thermal absorption in any case of tig). Spray is like special high penetration where the arc turns in into high velocity tiny droplets. When you energize the feed I assume you might get some extra velocity? but you still must weld right side up, short circuit is the only one that lets you weld above you. You can configure a expensive mig welder to do any of these processes.fourI assume you can build any size version of any of these machines, but I am pretty sure most jewelry ones are just tungsten tig without fillerHe uses a filler rod, its not fed from the electrode.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: May 04, 2025, 10:43:07 pm
content: As far as I understand, diyfella wants to devise a (pulse) TIG welder. It differs from vanilla TIG welding because there's no continuous arc, there are only individual spots.No HF/HV to light up the arc either, but just direct contact with the workpiece (same as 'TIG-lift') at each spot.The pulse arc process feature another major difference : the W electrode automatically moves back at each spot. I think this is unique and does not exist for any other welding process.

author: SteveThackery
author_rank: Super Contributor
timestamp: May 05, 2025, 09:26:56 am
content: Maybe we should avoid analogies with MIG and TIG, because the jeweller's welder I used deposited metal from the electrode to the workpiece, a bit like MIG, but without the shielding gas and without the continuous arc.There are two questions in my mind:1/ Is the polarity important in terms of which piece donates metal to the other?2/ Could the cratering described by the OP be a result of too much arc energy?

author: diyfella
author_rank: Newbie
timestamp: May 05, 2025, 12:46:27 pm
content: This is the device i'm trying to make :https://youtu.be/_G22BOr7Slk?feature=sharedIt's basically a tig welder for very small and delicate workpieces (like jewelry). the way it starts and arc is essentially the same as lift arc start that you would find in normal tig welders. but the welding happens in a very short pulse of high current from a capacitor bank rather than an inverter.I think my problem is in the arc initiation. it ends up being an explosion rather than a nice weld pool.It's basically the lift arc start part of it that i can't find much info about.If you guys have any references to this kind of circuit it would be appreciated.

author: Xena E
author_rank: Frequent Contributor
timestamp: May 05, 2025, 01:02:01 pm
content: Are you using shield gas?How are you controlling the timing and energy of the discharge?Kudos for trying to build your own, but commercial units are available from a few hundred USD...I have one like this, it works great!:-

author: SteveThackery
author_rank: Super Contributor
timestamp: May 05, 2025, 02:06:23 pm
content: Quote from: diyfella on May 05, 2025, 12:46:27 pmThanks, that's a very interesting video and I understand much more about what you want to achieve. I was wrong in my earlier post where I thought you were depositing from the electrode to the workpiece - sorry.I'm afraid I don't have specific subject knowledge, but I wonder if the arc current is too high. Have you experimented with some low value series resistors? And of course you've got the polarity right?

author: diyfella
author_rank: Newbie
timestamp: May 05, 2025, 02:09:43 pm
content: Yes i'm using argon for shielding, i normally have the electrode at negative but i have tried positive electrode as well.I have tried low value resistors and everything.I'm using an arduino due as the controller.I'm programmer first but i do electronics as a hobby and i'm very interested to get this circuit right because it involves both those things.

author: Xena E
author_rank: Frequent Contributor
timestamp: May 05, 2025, 02:27:11 pm
content: No expert on how these things work but I have the idea that the arc is initiated by HV low current supply in series with the main pulse, the actual charge on the capacitors, if you will, being the controlled quantity. Once the arc is initiated, the HV component is then quenched by the discharge of the main pulse, the secret sauce of course is in how this is all syncronised!X

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: May 05, 2025, 07:16:54 pm
content: Quote from: Xena E on May 05, 2025, 02:27:11 pmSame insights here.I don't really know how 'Lift TIG' (also named 'Lift arc') actually works.Could not really figure out if there's a HV at the beginning to ignite the arc or if there's just a small current that detects the short.High end TIG welders feature the 'HF TIG' mode that does not need contact between workpiece and the W electrode. What's weird is that HF stands for High Frequency and this does not spontaneously trigger sparks. Apart when youput a pan or cutlery in a MW oven.Another method is 'scratch start'.There must be anisolation issueon his welding equipementI would say the best way for diyfella to move forward is to find schematics of 'Lift TIG' welders. Maybe it will help to explain how the arc ignites.

author: coppercone2
author_rank: Super Contributor
timestamp: May 05, 2025, 07:32:40 pm
content: You need HF in any tig because the arc is unstable without it and likes to extinguish itself. At least with AC. For DC I am not sure. But its not like you can just drop the feature for the traditional tig welder and expect it to work.The HV might also help with the initial arc start (maybe accuracy)They call HF something along the lines of arc start ANDarc maintenance. I don't know what effect it has on a DC arc after its started. If its enabled it might help deal with arc flutter or something (like if there is air flow, popping (or other nonidealities that disturb the arc)But I do believe that the old scratch start DC only machines did not have HF, but I think I read or watched something that did say this HF-less technology is flawed.To me the HF is saying "no matter what happens, I guarnatee the arc will be ignited so long there is arc power and I am powered". I mean stuff like say gas forming from contaminants in the metal that get... reduced and generate gas from the intense heat, which can then disturb the arc on some level... maybe not extinguish it... but divert it, unfocus it, etc. Take this with a grain of salt to help your researchIt does seem less important for a short duration weld if its important at all for DC.It may help to paruse some manuals to see what they say about the HF feature, if it can be disabled. Miller makes their equipment kinda non adjustable/for stupid. Everlast might be more 'configurable' and they might say something about it.Its really hard to get the engineering details on welders, because from the consumer level they are really not going into details.. there is like a severely degraded series of analogies that are used to explain various complex behaviors (which have to do with complex electrical stuff in the end). Good luck

author: Xena E
author_rank: Frequent Contributor
timestamp: May 05, 2025, 10:38:04 pm
content: How this seems to work:After initiation the shield gas is turned on and the electrode is lifted. The point at which the electrode breaks contact with the surface of the work object is detected, and is when the arc pulse is initiated. After this the welder resets and waits for a further pulse to be initiated.The energy that is discharged into the arc is the controlled quantity... I'm not sure how it is controlled, however my impression is that if it were required to be done by capacitive storage, the stored charge would be controlled by the value of capacitance rather than varying the voltage across a fixed value. I don't think that attempting to control the rate of discharge of a fixed charge into the workpiece with a resistor will have any useful effect.The charge energy, and rate of discharge could be controlled electronically perhaps.I did quickly try to scope what was happening at the electrode with a ×100 probe but only successfully stopped the device from initiating a pulse! The only way to do that successfully is by using a non contact current probe perhaps, something I don't have access to at the moment.X

author: SteveThackery
author_rank: Super Contributor
timestamp: May 05, 2025, 11:19:19 pm
content: Quote from: coppercone2 on May 05, 2025, 07:32:40 pmThis is a pulse arc, not a continuous arc, so the rules seem to be different. The Gesswein video implies it uses DC because he says the electrode clamped to the workpiece is positive, and the handheld electrode is negative.

author: Xena E
author_rank: Frequent Contributor
timestamp: May 05, 2025, 11:31:08 pm
content: Quote from: SteveThackery on May 05, 2025, 11:19:19 pmSorry Steve, but that doesn't make sense 😵‍💫

author: coppercone2
author_rank: Super Contributor
timestamp: May 06, 2025, 12:12:57 am
content: Quote from: SteveThackery on May 05, 2025, 11:19:19 pmYou would need to know very well about to arc to say for sure... I am just suggesting not to totally gloss over it because its 'quick'. It might be a tricky mother...If you can image it with a slow motion camera and be sure nothing is happening.. that would be ideal.I justimaginedsomething like a bit of moisture or oil or chemical (solid -> gas because of heat) being vaporized and then disturbing the arc in the very short time period its around. That HF is usually in the ultrasonic frequency range, so it might POSSIBLY help compensate for some IRREGULARITIES even if the arc is around for a small period of time. There could be contamination on the surface, or under the surface, or in a scratch in the surface and it could do anything from blow a jet of gas into the arc to splatter microscopic amounts of weld material into the arc (if it say... makes a micro pressure explosion because it got super heated in a confined space and throws some metal into the arc, possibly chunks, or vaporized molten metal). Something between a pizza bubble popping to a tiny fire cracker in a big bowl of batter... I.e. what does jewelers rogue do when you hit it with a arc? I can see that being 'compacted' into a tiny scratch in the weld area if cleaning was insufficient.I am kind of thinking that it might be a 'luxury feature' though. The way it seems to be looked at in the welding industry is that some of these advanced features are basically quantified by something along the lines of "for x amount of weld made, y amount of weld defects needed to be repaired/touched up". Even with robot machines you have defects happenBut, reading this thread, I am thinking that the most likely problem is a current control issue........... it sounds like the OP is having problems with his controls measurements

author: SteveThackery
author_rank: Super Contributor
timestamp: May 06, 2025, 08:53:41 am
content: Quote from: Xena E on May 05, 2025, 11:31:08 pmI'm an idiot! Thank you - I've fixed it.

author: Xena E
author_rank: Frequent Contributor
timestamp: May 06, 2025, 11:07:46 am
content: Quote from: SteveThackery on May 06, 2025, 08:53:41 amNo, you're not.X

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: May 06, 2025, 12:24:24 pm
content: Quote from: Xena E on May 05, 2025, 10:38:04 pmForthat projet, the maker (devmonkey) explains that he mesures and servos the current at 100kHz so that the arc does not break down.Instantaneous power calculation (I x U) is performed at same rate and then integrated to determine the cumulative energy (in J or Ws, which is the same).Welding process is stopped once the defined energy amount is delivered.Yes, it is probably capacitive storage. Hence, we are talking about Farads rather than microFarads.Quote from: Xena E on May 05, 2025, 10:38:04 pmCould it be that the welder detected a ground fault through the GND of your oscilloscope ?It is almost sure that mastering the current waveform (and maybe adding some HF signal), and also the tip retract moment (and speed ?) has a significant impact on the weld quality.Here's anOrion welding equipement(about 3500 bucks ?). The result is just amazing.TheAli/Amazon welder(about 3-400 bucks) seems not to provide the same welding quality.But it might also depend on the skills of the user and the welder equipement setup.

author: LaserSteve
author_rank: Super Contributor
timestamp: May 06, 2025, 03:39:52 pm
content: We had an Orion at my former employer. There are two pulses. First one cleans the weld. Second one is the weld. Pulsed DC is used, the source is a cap bank, however there are minute adjustments for pulse timing, pulse length, pulse energy, delay etc. So there are some Semiconductors in the path. Looking at the web site that model is no longer made.It is lift start, when the solenoid pulls back the SHARP, THIN tungsten, a small sense current loop is broken, and the main pulse is dumped. Just before the pulse, the Liquid Crystal viewing window closes in sync with the machine via a cable. Keep in mind Argon discharges start very easily as opposed to Air. There was no evidence of a HF start at all. I found the foot pedal to be very desirable.Ours was abused, a long term user failed to use the shield gas often, before I took it over. This took a toll on the handheld. RTGDM is what I'd like to say to that person, and his students, as repairs were expensive. If you need a battery strip welder, buy a battery strip welder, is also what I'd like to say to the prior user, as they ran it at the energy limits. It is not for large welds.Care needs to go into the probe and solenoid design. The currents are beefy. The motion distance/speed needs to be very repeatable.My use was welding very tiny thermocouples to substrates.. Once the handpiece was repaired it did that very, very, well.

author: Xena E
author_rank: Frequent Contributor
timestamp: May 06, 2025, 04:10:00 pm
content: Quote from: timeandfrequency on May 06, 2025, 12:24:24 pmWell, it detected it, I'm sure... but not a ground fault as I was using a handheld...Quote from: timeandfrequency on May 06, 2025, 12:24:24 pmThe HF component may or may not exist as a deliberate feature, as there would almost certainly be HF oscilationbecauseof the spark. That remains to be confirmed.I'd definitely watch a teardown video!Skill yes, you can't just point and shoot, but it is a skill not an art.I would be sure that the difference in functionality of the two models would be obvious in the finished welding ... the Amazon one is OK but the adage of get what you pay for will apply without a doubt.X

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: May 06, 2025, 06:22:29 pm
content: Ben recently tested a systemfor filming TIG arcs.