Jack Davies | DIY Spot Welder From A Microwave
15146
post-template-default,single,single-post,postid-15146,single-format-standard,ajax_fade,page_not_loaded,,qode-theme-ver-6.5,wpb-js-composer js-comp-ver-4.4.3,vc_responsive

DIY Spot Welder From A Microwave

14 Feb DIY Spot Welder From A Microwave

thumb_IMG_3577_1024

This project is an outline of how to build a resistance spot welder using salvaged parts from an old microwave. I’m using it to weld nickel tabs onto 18650 battery cells but depending on how you position the arms it can be used to weld sheet metal and other metals objects. Lets get welding!

 

Step 1: Salvage the Microwave

thumb_IMG_3423_1024
thumb_IMG_3426_1024
thumb_IMG_3427_1024

Quick note of caution!

The inside of the microwave is quite dangerous. The large capacitor maybe charged and can deliver a nasty or even fatal shock so ensure you discharge as soon as possible by touching a metal rod such as a screwdriver across the terminals to discharge it.

Okay so open up the microwave casing to reveal the electronic bits. Discharge that capacitor and get to work on removing the parts. You should find the transformer which should look very similar to the one in the photos. Remove the nuts and it should slide out pretty easily. I salvaged a few limit switches that we will use later and some of the cables are handy for power connections.

 

Step 2: Remove The Secondary Coil

 

thumb_IMG_3449_1024 thumb_IMG_3459_1024 thumb_IMG_3462_1024

We are going to rewind the secondary coil of the transformer as we want more amps and less volts. The primary is where the mains power is attached and the secondary has finer wire windings with the red wires attached.

The fewer turns of wire increase the amps but lowers the voltage, and more turns increase volts while reducing the amps. We don’t need the secondary coil so it can be removed either by cutting off or by grinding the weld on the transformer body and sliding it out. Be careful not to damage the primary coil as we will be keeping this.

 

Step 3: Add The New Winding

 

thumb_IMG_3472_1024

thumb_IMG_3588_1024

The new winding will provide the current needed to weld stuff. By using really thick cable we can reduce the thousands of windings to a couple which will provide loads of amps. The thick cable is needed as the resistance will cause it to heat up and melt the insulation if its too thin. Not good!

The primary coil is put in first followed by the 2 shunts either side and finally the low gauge wire (blue cable) is wrapped a couple of turns. Remember to leave a decent length of cable that will attach to the welding electrodes.

 

Step 4: Finish The Transformer

 

thumb_IMG_3583_1024 thumb_IMG_3592_1024

Our super high powered transformer is nearly complete. We just need to weld the top back on to seal it up. You could alternatively use 2 part epoxy to stick it on. Options are good, pick whichever one is easiest for you. šŸ™‚

 

Step 5: Electrode Terminals

 

thumb_IMG_3569_1024thumb_IMG_3509_1024thumb_IMG_3497_1024thumb_IMG_3503_1024

We now need to attach our cable ends to the copper pins which we will use to weld. I machined some copper terminals but you could use some copper clamps from the hardware store. I’ve also attached the CAD file for the electrode clamp that I made. Here’s the Fusion360 link too. http://a360.co/1Loyh1j

 

Step 6: Welding Arm

 

thumb_IMG_3555_1024thumb_IMG_3563_1024thumb_IMG_3561_1024thumb_IMG_3567_1024

I’m using this to weld nickel tabbing to battery cells so I’ve positioned the two welding electrodes side by side although you can easily mount them opposing like a traditional machine. I designed and laser cut a simple MDF case for the arm which houses the switch for operation and holds the electrode terminals.

 

Step 7: Package It Up

 

thumb_IMG_3598_1024thumb_IMG_3596_1024thumb_IMG_3605_1024

There is 230v of dangerous electricity coming into the transformer so its important that its covered. This laser cut case should do the job pretty well. Just make sure everything is contained as it will also look much better as well as being safe. Bonus!

As for wiring its pretty simple. Just connect the live and neutral to the transformer primary using the existing spade terminals, I would recommend adding a switch in between one of the power cables to make it easy to turn on and off. I salvaged this one from the microwave.

Thats it we’re done! Have fun with your new spot welder!

7 Comments
  • Beulah
    Posted at 05:54h, 04 August Reply

    I’m truly enjoying the design and layout of your site.
    It’s a very easy on the eyes which makes it much more pleasant
    for me to come here and visit more often. Did you hire out a developer to create your theme?
    Excellent work!

  • Marge
    Posted at 21:37h, 04 August Reply

    Good day! I could have sworn I’ve been to this blog before but after checking through some of the
    posts I realized it’s new to me. Nonetheless, I’m definitely delighted
    I found it and I’ll be bookmarking and checking back often!

  • Ash
    Posted at 13:37h, 10 August Reply

    Thanks for sharing your thoughts.
    Regards

  • Zelma96
    Posted at 23:59h, 13 November Reply

    Reading your content is pure pleasure for me, it deserves to go viral!

  • Mike
    Posted at 13:13h, 14 April Reply

    Hi, great article on the spot welder. Would you mind sharing the laser cutter files for the enclosure?

  • Scott
    Posted at 19:27h, 08 March Reply

    I am excited to try this out myself after picking up a $10 microwave off Craigslist.

    On a semi unrelated note, what make and model of laser cutter do you use? Iā€™m overwhelmed by the number available and the fake reviews and quality variations on the diy cutters.

    • Jack
      Posted at 21:45h, 03 July Reply

      Hi Scott, sorry for such a late reply. I don’t monitor the comments here very often!

      I used a Universal Laser Systems cutter for this, which was at my university, however it has been a few years since that now, but it was very nice to use.

      Hope that helps!

Post A Comment