Replacing a burned out resistance welder
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  1. #1
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    Default Replacing a burned out resistance welder

    We have an older Miller hand held resistance spot welder that stopped working. Took it to our local welding supply and they said the transformer was dead and it was an obsolete model so we should just go buy the cheapo Horrible Fright one, which doesn't have as deep of a throat as we need anyway.

    So I'm shopping around and could use your input. We don't do really heavy stuff, 1/8" steel total stack is the max we would see. We use it to make small machinery belt guards and such. 16" tongs or thereabouts. I've called a few welding supply companies and it seems that they either don't do resistance welding, or aren't aware of "local" companies that do. One Houston company told me the only one they were aware of was T.J.Snow in TN, but my next google search came up with a company in Dallas, so it's a little confusing. I thought Resistance welding was a little more common.

    One other option I'm considering is going the DIY route, but not with a microwave transformer, lol. A foot operated unit would be much more helpful and I've seen where you can buy transformers and other components individually for custom set-ups and we already have a few lighter duty foot presses on hand, so I'm wondering if I could just adapt the tongs to one of those and wire them into a transformer. I know you can buy foot operated units but it seems that the used ones start at a few thousand dollars and go up from there which is a little out of the budget right now.

    So, any thoughts? Any reputable brands to look towards? Anyone else professionally build their own? I'd love to stick with Miller, but I've gotten conflicting stories from different shops about if they still make/support the stuff and their website is no help on the topic. We don't see as high of a volume of spot welding as a sheet-metal goods company, but does that really drop us in the front door of HF?

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    Could you adapt the transformer from the HF unit? Then you would still have the better throat depth of the miller unit.

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    HGR get's in welding xformers, assuming from the automotive plants.
    Used Machinery & Industrial Equipment | HGR Industrial Surplus

    I did just what you want, got one from HGR, and made a frame with electrodes, and heavy cables.
    It worked o.k.

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    Quote Originally Posted by Scottl View Post
    Could you adapt the transformer from the HF unit? Then you would still have the better throat depth of the miller unit.
    I suppose. That would prove the concept then if/when we burn it out we can buy a better generic resistance transformer. The press's I have in mind are old industrial textile ones used for stuff like individual rivet setting and such. I'm envisioning just bolting the transformer to the back of the press and using copper cables to connect to the points/tongs, which would need to be mounted so they are isolated from grounding through the machines frame. Then I could set up a limit switch that would turn on the transformer via relay when the press bottoms out.

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    540x360.jpg

    The press I would use would be similar to one like this.

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    Another question would be where to start in making sure I get the right size of transformer for our application? 110v would be ideal, but we can put in a 240 or 440 drop if needed. Is it based on work thickness alone or are there other variables?

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    If you didnt need a hand held unit, I know miller makes a nice spot welder. I cant remember the numbers and I dont work at that shop anymore, but I can find out what it was.

    When that shop upgraded they went with an Italian unit. Same story with the numbers and who made it.

    I did thousands of spot welds with the miller. 16 gauge up to 1/8" with the miller and up to 1/4 with the Italian unit.
    The italian job was fancy and had computer control and many buttons and displays. The miller was a transformer with a pair of analog timers. Both were 480 3 phase and not hand held.
    The italian machine was more precise, but tedious for production. It had a mechanical foot pedal that controlled the tongs and cycle. Air power took over once the cycle started, but you positioned the tongs with the foot pedal before the cycle started. The miller was air powered and the foot pedal was just a switch to trip the timers.

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    The older Miller resistance spot welder transformers were pretty much in destructible. That said there is the exception.
    Before you toss it I would check some of the basics, if you understand the basics of transformers then I would check to confirm that the transformer is either shorted open or the winding are arced across, could be something as simple as a timer control, trigger switch, input power cord or loose wire connection. I have seen more then one of these tossed because of something simple.

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    Miller spot welders work well but Miller no longer makes/sells them. I have 2)220 volt Millers and 1)110 volt. One of the 220 volt units is mounted on the foot operated stand that Miller sells, another on a gyro bail. 110v is hand held sometimes and I made custom tongs for it. I believe the HF units have replaceable tongs and some places like McMaster or MSC may have some still in stock. I bought a 6' bar of the same hard copper alloy (.625) to make my tongs and tips.
    TJ Snowden has 110/220 volt units with sim specs to the discontinued Miller units. They look to be more compact and have the timers built in to the unit. Can also find a lot of Miller units on Ebay.

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    I've got a couple upcoming jobs that I'm waiting for some blanks to arrive that we'll bend and weld together. We still have a bunch of extra tips for the Miller, so If I can find an appropriate transformer I want to give the DIY option a shot and I'll build it to use the Miller parts. I think Millers thread-in tips were proprietary to them, but It wouldn't be too hard to make adapters for other styles of tips if needed.

    The press I need to get pulled out of our warehouse, and it only has a 12" deep throat, but the bar that supports the bottom anvil/tip is replaceable so I'm thinking about replacing it with a 'U' shaped copper tong that should allow us to reach all of the points we had in the past with our Miller. I don't think there will be a whole lot of custom fabrication to it. The worst of it will be making copper adapters for the top and bottom and than making insulators that still allow the copper bits to be firmly held in place. The rest is some electrical.

    If I get in a bind, I can MIG the sheet metal together too, but I'd like to get a spot welder back on the floor, and a foot powered unit would be so much more helpful than the hand held ones.

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    Quote Originally Posted by M.B. Naegle View Post
    I've got a couple upcoming jobs that I'm waiting for some blanks to arrive that we'll bend and weld together. We still have a bunch of extra tips for the Miller, so If I can find an appropriate transformer I want to give the DIY option a shot and I'll build it to use the Miller parts. I think Millers thread-in tips were proprietary to them, but It wouldn't be too hard to make adapters for other styles of tips if needed.

    The press I need to get pulled out of our warehouse, and it only has a 12" deep throat, but the bar that supports the bottom anvil/tip is replaceable so I'm thinking about replacing it with a 'U' shaped copper tong that should allow us to reach all of the points we had in the past with our Miller. I don't think there will be a whole lot of custom fabrication to it. The worst of it will be making copper adapters for the top and bottom and than making insulators that still allow the copper bits to be firmly held in place. The rest is some electrical.

    If I get in a bind, I can MIG the sheet metal together too, but I'd like to get a spot welder back on the floor, and a foot powered unit would be so much more helpful than the hand held ones.
    HF welders look to have replaceable tongs about .625 dia. But I think they are copper plated steel? Or just tips copper? Miller tongs turned to fit into HF welder.

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    I have six of the portable spot welders. The Miller Hobart Dayton are all pretty much the same machine.. We stopped using the portable ones about 4 years ago and switched to larger machines. The smaller Miller's are either 1.5 or 2.5 KVA. I find 10 KVA to 20 KVA to be about the right size, they can be controlled with digital timers, if you run a water chiller the tips last around 10,000 to 40,000 welds before adjusting or dressing the tips. The Miller tips are actually kinda terrible.

    Just look up spot welder and 10 15 or 20 KVA. Also check Facebook market place or Craigslist.

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    can't imagine its worth your time to cobble up your frankenwelder thingy. ok if you are a hobby guy looking for a project, maybe, but I'd still advise strongly against it.

    I think those lightweight grommet presses from the rag and bag trades don't have the force to make a good ERW either, especially if you extend the jaws.

    get the HF crap if you need one right away, and shop for a real one at auction or a direct sale.

    for really low volume, just GTAW (or GMAW if thats all you have, but much messier) plug weld and keep an eye out for a bargain on an old miller or other foot operated unit.

    (if you are thinking of sending it out, how about having it TIG plug welded, way more job shops are going to have a TIG than a spot welder? if you pre-drill and clamp I'd think it would be something like 1$ a weld. check what they want for hole size and clamping setup, but i think something like 3 times thickness is about right for the hole in that thickness range. a copper chill plate on the backside is the key to doing sheet meal TIG plug welds! )

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    If the transformer is US,why not rewind it.....there is no way the secondary could burn,and the primary is quite thick wire......in fact ,i suspect you could salvage the wire and re use it wit a bit of epoxy and cloth for insulation ....Ive scrapped lots of spotwelders,bulk copper in them ,so I suspect a newie would be spendy.

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    The most common thing to go out on them is the switch. Best I ever got out of the manual switches was around 5,000-10,000 welds. I ended up converting mine to use 40 amp contactors and just ran another control wire out heat shrinked to the power wire.. Contactors last about 20,000 actuations. I have yet to burn up an quality spot welder, just don't let them get hotter than you can hold your hand on and generally they will just keep working.. The Harbor Freight ones will sometimes burst into flames, the aluminum windings they use do not tolerate overheating even within the reasonable working temps of not going above hot to the touch.

    Two other problem areas are the insolation on the bottom tong connection, and the shunt cable to the top tong.. As I stated above, I stopped messing around with these little ones years ago when I figured out there are older industrial sized pedestal spot welders on ebay, craigslist or facebook marketplace for about the cost of two harbor freight spot welders you can have one that can weld all day long provided you can supply cool water to them. Just a 5 gallon bucket with a fountain pump will get you about 1,000 welds before the water is over 100 degrees.. If you want to cook up your own chiller unit, a through wall AC unit with a radiator mounted in front will keep five welders reasonably cool.

    I need to make a video about my adventures in converting old foot pedal operated spot welders to pneumatically operated with digital timers, I have done 7 of them and all are still chugging along. The first ones used PLCs but then I figured out you could build a better one with a pair of inkbird digital timers operating a series of three 8 pin ice cube relays. Whole set of conversion hardware was around $200 and they work very well. If you feel OK mounting a transformer to a press frame that a slight rework on an existing machine should be vastly simpler.

    I do have to restate that the bigger units are so much easier to use once you get over the learning curve. The setup process is so much easier than a portable because you can actually adjust the tips to match and make a nearly perfectly smooth weld every single time. I would not get hung up on the value of the miller tips. Once I switched I never looked back.

    Honestly if you want a whole set of four portable spot welders two of them millers on a stand setup to weld on a timer, I have just such a setup that I've been trying to sell on craigslist. Only problem is I'm near Daytona beach Florida and it looks like your in Texas.

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    One issue we've had with outsourcing these parts is that they either come back sloppily assembled, or they get over-tolerance'd/over-quoted. We like spot welding them because it's quick and simple with very little training while the operator can still make a geometrically square assembly.

    We have a sheet metal shop that we used to outsource a lot to that did a very good job, but they're 3 hours away (where our shop used to be located) and there was always a lot physical of back-and-fourth proving the design and assembly before we could go into production.... making 10 pieces every 6-12 months. It's way more economical to be able to prove the design and construction ourselves and then have our own shop hand throw them together.

    I'm keeping an eye out for a floor model Miller or anything else in the greater Houston area. If my DIY thing takes any shape before then, I'll post the results.

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    Dan Gelbart had, as I recall, a decent YouTube video describing his DIY (but for a professional prototype lab) resistance welder. Might be some useful insights there...

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    If you are looking at pedestal spot welders I highly suggest not getting a miller. Miller makes a lot of great welders but their big spot welders are all kinda terrible compared to others.

    I have Alphil, Federal, Eliser.
    Other names I've seen, taylor, acme, lors, thompson. Basically names you've never heard of but all big spot welder makers. They all pretty much operate the same, use generic industry standard parts and have operational life times measured in decades or centuries rather than months or years.


    Here is one of my converted welders. It uses:
    2 inkbird IDT-E2RH timers to control the weld and post hold.
    3 12v dc 8 pin din rail mounted relays
    1 normally open pressure switch
    1 2 amp or larger 12v dc power supply.
    4 50 amp rated 2 pole 120v coil contactors with the poles linked to function as a single pole.
    1 12vdc 5 port two position solenoid valve (option add another for pneumatic clamping fixture)
    1 foot switch (option add another if installing pneumatic fixture function)
    1 50mm (2") bore pneumatic cylinder, on mine I use a 40mm stroke which is right around 1.5"
    1 estop switch.
    1 pneumatic regulator

    And a pile of push connectors and tubing, bolts, weld wire, lots of machine wire, some fuses, a project box to house it all, most of a weekend and a case of beer to get you through the assembly process.

    The first two contactors from line, one controlling L1 and the other controlling L2 are controlled directly by the E-stop. Pushing the foot switch activates a relay which activates the solenoid and sends power to the pressure switch and applies power to the timers and also activates L2 contactor to the transformer. Once the welder closes and the pressure switch triggers, power is released from the timers which activate, the welder timer activates a relay that throws L1 contactor to transformer, and the post hold timer activates which locks the relay that controls the solenoid.

    If anyone is interested I can do a more detailed view of the conversion and draw a wire diagram.. I could also supply links to the parts since they are all still in my order history.



    There are 6 welders down the wall, the 5th and 6th are not very visible as they are tucked beside a old index cabinet that holds fixtures, and the water cooler setup mounted on the far wall. The blue barrel is a 13 gallon drum that is the water tank for the cooler there is a pump in the tank that circulates water to the welders and back to the radiator in front of the AC system. if I turn the AC unit all the way to max it will get the water to around 63-F in about two hours. I run it a little higher as I want to keep the water a few degrees above dew point to keep condensation away.. With cool water the tips hold their shape about 10-20% longer than with warm water.

    If its just a few welds with an hour or more between, you don't need liquid cooling at all.


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    Thanks csspecs for all the good info.

    We also build and service heated embossing press's, such as would be used to emboss a company logo on a belt or someone's name on a book cover, and I imagine that the pneumatics and dwell time controls would be the same, so we have a lot of parts and components on hand for that.

    As far as the Miller "tooling" goes, it looks like the threaded tips are what makes them special, while others have a tapered engagement(?). Are there different sizes of taper systems and if so which one would be the most available to work with?

    What is used to conductive-ly insulate the upper and lower arms on these machines? I think the hand held units have some fiberglass pads in between the frame and the blocks that clamp onto the copper tongs (It looks like in terms of hand held welders that the 5/8" copper rod is pretty universal). Is the insulation the same on the bigger machines?

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    Yeah same concept on the time control. You don't want the transformer coming on unless the machine is going to stay clamped shut, otherwise you will be getting sprayed with melted metal. And in my case I want to be able to hold the foot pedal and not have the machine double fire. Because on some parts its nice to be able to pull the fixture off before unclamping the part.

    As for the tips, yeah pretty much all the other tips are tapered, the normal taper size is #4RW and #5RW, which are Morse taper 1 and morse taper 2.. Welders larger than 20 KVA often use larger #6RW or #7RW and my understanding is that they are morse 3 and morse 4. But I have never used them so I don't know that for sure. The Mt1 = #4rw and Mt2 = #5rw is something I know because I have made my own custom holder arms.

    Multi tip welding is another great trick if you need to kick out a bunch of welds in a hurry.

    One of the better places I have found to buy tips is RW electrodes. Download the PDFs for the different manufacturers and then figure out how the part numbers work. The tips last a crazy long time. I bought a bunch of them back in 2015 and I have yet to throw any away, I'm pretty sure I'm well over a couple million welds since then, just dressing the tips with a file from time to time. Also type 1 & 2 can be filed, type 3 tips should never be filed as the dust is hazardous, something to be aware of.
    Resistance Welding Supplies | RWElectrodes.com — RW Electrodes

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