Welder

Discussion in 'The Projects Forum' started by MikeL, Nov 19, 2008.

  1. MikeL

    Thread Starter New Member

    Aug 12, 2008
    9
    0
    Here's the back story, I've been working on chain Maille projects for a few years now, everything from micromaille to armor.
    Recently, I decided to build a welding aparatus in order to close my links permanently. I havent begun building yet, or even collecting supplies as I am still in the 'design' phase.
    I've heard of people building spot welders out of cannibalized microwave transformers as well as capacitor discharge welders.
    I havent decided which type I am wanting do. i've found decent plans for building both, though I question which would work better.
    Here is the link to the capacitor discharge welder i found.
    http://www.philpem.me.uk/elec/welder/
    I planned on tweaking the design a little bit, as some of the parts have not been easy to find.
    the better looking plans for the transformer based one I found through www.instructables.com

    I guess my overal purpose in posting this, is I need some advice. I'm not quite sure on all the pros and cons of using one vs the other. (I am especially rusty on my capacitor theory) I plan on using it for several different gauges of wire and for wires of different composition. I was also thinking of using different size electrodes based on the wire gauge I am welding. I know I will need to be able to vary the amoung of current being output through the electrodes, though if i go with the capacitor discharge welder, would I also be able to vary the duration of the discharge.

    I appologize if my thoughts aren't entirely coherant. I am open to any and all suggestions/comments, etc.

    Thanks in advance.

    Mike
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,699
    905
    I have built both the Poor Man's Battery Tab welder and a microwave transformer based (MOT) welder. I designed a zero crossing trigger and timer on the microwave device so I could control the number of cycles.

    Both worked. For battery tabs, the capacitor discharge gave a smaller heat-affected zone. Welds were through and quite strong. With small bore (0.188 to 0.25), thin-wall SS tubing, the capacitor gave a very nice tack weld that held up to brazing. The MOT was just too much heat for my liking.

    For my capacitor discharge welder, I used #4 cable for the added flexibility compared to heavier cable, 1/4" copper electrodes, and compression fittings. My best results were obtained with 16 to 22 V and 432,000 uF. I tried a variety of audio capacitors (up to 3 F), but the limitation on voltage is a problem for the thicker SS tubing. They do work, however, for battery tabs. Remember that Joules goes up as the square of the voltage. I will try to find a table I made comparing semi-quantitatively weld strength with voltage and capacitor size for thin steel sheet and post it tomorrow.

    John
     
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