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Thread: PUK welders

  1. #41
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    The lovely man from Suttons let me play with the PUK welder this evening. Now I really want one! Am officially saving up whilst I still have my day job.

  2. #42
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    Did you try a laser as well to see the difference in behaviour?
    I might know of a 2nd hand PUK if you need.

  3. #43
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    I didn't try the laser as well out of my affordability range. The boy looked at me in horror at the price of the PUK as it is!

    Will be a while yet before I'm even in a position to think about a second hand one, but thanks x

  4. #44
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    When you can take the expensive toys for a test-drive, carpe diem!

  5. #45
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    Aug 2009
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    Haha, Peter....you BAD boy........such a bad influence!!

  6. #46
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    He is, isn't he? I don't need any more encouragement, I'm already sold on the thing!

  7. #47
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    Me too. That's what I'm saving for as well.

  8. #48
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    dear old Blighty - (in deepest Wiltshire)
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  9. #49
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    Quote Originally Posted by Tabby66 View Post
    Haha, Peter....you BAD boy........such a bad influence!!
    Sorry

    What I was meaning was more that if you've got an opportunity to try both, do so - not from the point of thinking of buying the more expensive one, but you can get a direct impression of what the differences are between the 2. Day before yesterday I was rebuilding a setting on a ring with the laser; whoever had made it did not provide a seat for the stones, so funnily enough they rattled around... Using the laser I was able to deposit a continuous bead of metal around the inside of the setting, then recut it to form a seat. While PUKs can do continuous welds, they're very much slower - I was running at 3Hz for that. Also, there were points where getting an electrode into the thing would have been awkward; because I had line-of-sight on the weld I could move metal around to suit.

  10. #50
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    Mar 2020
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    Jülich, Germany
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    Quote Originally Posted by Binraker View Post
    Yes it is a little more complex. The idea is basically a mechanically actuated scratch start TIG welder with arc timer. The magic is in the timing. The order of actions is something like: turn on gas, wait a bit for it to flow and cover everything, start electrode retract (it will take a millisecond or 2 to get moving and we want to turn on the caps just before the electrode leaves the surface, wait a few milliseconds, turn on cap bank, wait the desired amount of weld time, turn off cap bank, wait a bit to allow the user to remove the item, turn off the gas and release the electrode. It's all millisecond stuff so its not fast but it is "fast" from a human point of view.

    You can then select the charge voltage and arc duration to vary power and total energy supplied. If I had found it useful more I would have put in a number of parallel systems so that you could profile the voltage throughout the weld cycle and get a bit more control. you could also change the retract solenoid voltage to change the mean arc length or have a shorter retract distance so that full retract is at optimal to distance. or you could use an overlaid high speed high voltage ionising pulse to start the arc which will give more arc profile control but will limit your ability to weld into corners. There are numerous possibilities...

    The switching of the cap bank needs to be fast (sharp edges) and low resistance so very careful selection of transistors required MOSFETs will do the speed but not the power so you really need an IGBT with a hard driving circuit to keep the speed up. this needs to turn on an off in 100us territory to stop the transistor dissipating too much energy. The inherent ESR and ESL of the cap bank with throttle the energy dump quite a bit so it will probably be the limiting factor.

    If you want I will post all the details of my machine and the code if you want to build a copy of it as a starting point for your own investigations.
    Coming to this Post after a very log time. But this the first working home made PUK-Welder I found. Is your offer to post details still valid?

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