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I need to make around 500 or more thermocouples type J 30AWG per year. Currently I am using this thermocouple welder.

The process is quite tedious. I need to strip the wire, sometimes twist the wire, use the pliers to hold the thermocouple, and weld it. The success rate is not 100%; sometimes I fail to weld it into a bead. The machine is around 6-7 years old.

Currently, I am not sure whether should I build a new one (I have no idea how to build a thermocouple welder), get a new thermocouple welder, or to make a fixture that will help to make the process easier (any ideas on the fixture?).

ocrdu
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Terrance
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    Using a reducing or inert atmosphere may help weld quality. Have you considered asking this question on a metalwork site? – Jasen Слава Україні Dec 29 '16 at 06:51
  • We made 'em using a lab power supply (5A current limit, iirc). But only needed one here and there, not anywhere near the quantity you're talking about. – SteveSh Nov 30 '20 at 20:48
  • [This one looks good](https://www.amazon.com/MXBAOHENG-Thermocouple-Thermocouples-Temperature-100V-240V/dp/B081RNVVJZ/ref=sr_1_6?keywords=thermocouple+welder&qid=1638638068&sr=8-6), uses argon for shield gas. If you are building your own, I would consider an [induction heater](https://www.amazon.com/KOOBOOK-Voltage-Induction-Heating-Flyback/dp/B07WD9KZ4J/ref=sr_1_27?keywords=induction+heater&qid=1638638427&sr=8-27), along with shield gas. – jay Dec 04 '21 at 17:23

2 Answers2

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While not terribly safe, a welder for such thermocouples can be as simple as a light bulb (to limit current), a carbon electrode, and a clip to hold the twisted thermocouple wire just behind the weld.

And, an AC cord that plugs into the wall. Like I said, not terribly safe. We put the thermocouple wire into an insulated box, with the clamp holding the stripped and twisted thermocouple wire end, and advanced the electrode until it was nearly touching. Plug in the AC, nudge the electrode (it will touch the wire, start an arc, and the light bulb will light up). When the bulb is hot, and the wire melts and forms a bead, the arc will extinguish. Unplug the AC before removing your thermocouple.

schematic

simulate this circuit – Schematic created using CircuitLab

Whit3rd
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  • it seems that the safety of this setup could be much improved by the addition of an isolating transformer (in the supply). and an interlock on the box lid. – Jasen Слава Україні Dec 29 '16 at 06:21
  • Yes, or a ground-fault interrupter. What we actually used, was rubber gloves and a second person standing by the power plug, ready to yank it and/or do CPR. We didn't need lots of thermocouples. – Whit3rd Dec 29 '16 at 06:29
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    this seems to be a commercial version of your setup: http://www.omega.com/pptst/TL_WELD.html but at 2 grand may take a while to pay for itself at 500 thermocouples per year. – Jasen Слава Україні Dec 29 '16 at 06:51
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Buy a decent brand of TIG welder and rent or buy an argon bottle to go along with it. Make sure the low end goes down far enough for the minimum wire size you want to use. AWG 30 is fairly fine so you might need to go down to a few A. Air cooled torch is fine.

Bead thermocouples are dead easy, you should never get a bad one.

You can also get machines to help with stripping off the insulation. Clean wire that is not nicked is essential.

Spehro Pefhany
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