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Battery spot welder

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by jpanhalt, Jan 29, 2008.

  1. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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    I have had a couple of questions and received great help in adapting a capacitor-discharge spot welder design that was originally referenced by Pommie (See: http://www.electro-tech-online.com/threads/why-the-dip.35601/ ; and http://www.electro-tech-online.com/threads/zener-reference-voltage.35232/ ).

    I appreciate it when contributors post follow-up , but noticed the titles for those other threads did not mention spot welder. So this thread is iniated to give follow-up and includes spot welder for subsequent searches.

    The design basically follows the idea of Phil Pemberton (http://www.philpem.me.uk/elec/welder) and was modified to include a debouncer for the foot switch and a Variac rather than adjustable regulator for the DC power. I wanted more current to charge the capacitors. I also used audio stiffening caps of 1.6F and 0.5F rather than a bank of computer caps. The 0.5F (Scosche brand) seems to give slightly better welds than the larger Pyramid brand, but that result is preliminary.

    So, here are the results. The overall photo shows the prototype setup with the electrodes, capacitor, and debounce/triggering circuit visible. The two weld photos show a razor blade with a strip from a battery welded to it. The other shows the reverse side after the weld had been pulled apart and is intended to show the good penetration. Welding strips has been a problem, as it seems easier to blow holes in the material than to get a good weld. I will probably dull the tips to my electrodes to see if that helps. I used reclaimed battery tabs as the price for nickel sheet (0.004) has skyrocketed.

    The next experiments and modifications will include using an IGBT to perhaps shape the discharge time, maybe a short blast followed by a longer one (using two capacitors) or using a cheap 90A tig welding supply ( about $100 at Harbor Freight).

    Any comments or suggestions will be welcome.

    John
     

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  2. mikep_95133

    mikep_95133 New Member

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    Hi John,

    Glad to see that you are not just satisfied with a run of the mill cd tab welder. I'm interested in tab welding together some of the A123 cells I have for my electric truck. So I am following your progress with great anticipation.

    I've often thought that if the shape of the pulse could be controlled like on the professional welders, that higher quality would be the end result.

    It will be interesting to see the results of your IGBT testing.

    Mike
     
  3. fritz911

    fritz911 New Member

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  4. dave

    Dave New Member

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  5. Mickster

    Mickster Well-Known Member

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    Impressive Fritz. :)
     
  6. Sceadwian

    Sceadwian Banned

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    Too bad you can't use it on IC's.
     
  7. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Nicely done. I would be interested in seeing the schematics and overall design too!:)

    What is its upper limit welding wise?
    Have you considered using tungsten rods for welding electrodes? They take much higher temperatures before they weld themselves to anything.
    I made a set for may Miller 2.5 KVA resistance spot welder. I run it with a variac and drop the current and voltage and then focus the spot weld further with the tungsten rods sharpened to a dull point.
    I just took a worn out set of copper electrodes and drilled holes in the ends and silver brazed the press fit tungsten points into place.

    But I cant do anything near as small as your showing! :(

    But on the upside Mine is 240 volt powered and can spot weld three 10 gauge sheets together at once! :eek::):D
     
  8. KMoffett

    KMoffett Well-Known Member

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    I too have a 2.5KVA Miller spot welder, and I routinely weld 0.010 stainless together. After looking at the cycle-timer that Miller sells, more $$$ than the welder plus stand cost, I made my own timer. It times in increments of 16mS, one 60 Hz cycle. I like the tungsten electrode adaption.

    ken
     
  9. fritz911

    fritz911 New Member

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    Thanks guys

    tcmtech, my welder compares to the welders that Sunstone Engineering - Fine Resistance Spot Welders, Weld Heads, and Welding Accessories
    is selling. and puts out 600ws. This welder was not made to weld very thick metals. Its more for like welding battery tabs when rebuilding battery packs because it does not heat the area being welded up. I welded bottle caps together, jewelry and wires. It is very adjustable and can weld the finest stuff. For what i use it for my tips will last forever.
     
  10. fritz911

    fritz911 New Member

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    This welder compares to the welders of Sunstone Engineering - Fine Resistance Spot Welders, Weld Heads, and Welding Accessories and puts out 60Ws more than their $5400 welder. If i need to weld big things, I would build one of that microwave transformer welders. I've welded bottle caps together which is about 0.05", jewelry, copper wire and many more things. I mainly made this welder to weld battery packs and the energy i use is about 72Ws....it can go up to 600Ws. The welding tips on this welder does not get damaged by welding battery packs and will last very long. With the pulse width and voltage adjustment It can weld very fine wires and things like jewelry.
     
  11. fritz911

    fritz911 New Member

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    I see Sunstone brought out a new welder with a digital display and they changed their volt setting to Watt Seconds and the time of the weld to Joule. Ws And Joule is the same thing but I decided to change my machine's YouTube - Capacitor Spot welder display too.
    This weekend i used my CNC machine to make a hand held attachment for my welder...here are the photo's:
     

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