Tuesday, June 18, 2013

See Spot Weld

See Spot. See Spot Weld. Weld Spot, Weld!

While it takes me a long time to get to some projects, as you can see from the pictures, the spot welder is finally operational. The process of building this thing should have been easy but I had nothing but problems. The very first problem was caused by dismantling a transformer in less than optimal way that ended up separating some of the plates. I decided to dig up another recycled microwave which wasn't too hard to do. Due to other priorities, the project was pushed to the back burner.

Removing the Secondary Winding
Well, yesterday, I finally tired of looking at the donor microwave and tackled the project head on. It took some effort, but I managed to locate everything I needed except a momentary contact switch. With a saw in hand, I set about making a crude case as well as a set of jaws for holding the electrodes. For electrodes, I simply used 4 gauge solid core copper wire. I cut a one inch piece for each jaw and clamped it inside of an electrical lug holder. After several fit, tear apart, refit sessions, I had a welder sitting in front of me waiting to be tested.

The Partially Assembled MOT-based Spot Welder
My first test was with the jaws wide open. I plugged it briefly on a breaker socket. I heard the familiar buzz of a microwave and didn't see sparks flying so I clearly got the winding right on the transformer.

My next test was to find a suitable material to weld. The wire I used for making my sculpture provided the guinea pig test subject. I sanded down the paint until I could see shiny metal. I then carefully placed the wire between the welder's jaws and closed them. Not touching the wire, I plugged the welder in. Sparks flew as the power surged through the wire but settled down immediately and only a buzz remained. I counted for three seconds before unplugging the unit. The wire had fused into one piece. It's not a rock solid weld, but it did the job. I'd call it a success even if it's not up to welding the hull on the Titanic. At least that's the bulk of one task completed. Only about a million more to go.

Wire After a Three Second Weld

The Postmortem

As with all projects, there are things I would do different now that I've been through the process. One major change would be to use 2 gauge wire rather than 4 gauge in the secondary winding. It would provide more current to weld with. Using a pair of transformers might be another option for increasing amperage but finding a  matched set of cores might be a challenge.


How To Sources

Most of the ideas on how to build a spot welder came from the web. Hackaday is a great source of inspiration for projects like this and as always, they had a useful tutorial on how to build one a spot welder from a MOT. Among other useful links I stumbled across, Home-WorksShop.com had a decent article too. And since things usually go better in threes, here's another link to Mike Worth's project spot welder.

Onward and Upward

Now that the welder is functional, it's time to move on to other projects. To be certain, I'll make use of this little machine but mostly likely to temporarily tack weld small wire fixtures. My oxy/acetylene torch will fit the bill when it comes to making stronger welds. And if ever the day arrives, a TIG will be the crowing jewel. Now that's sweetness if there ever was any - well, mechanical fabrication sweetness that is.

So what's up next? With school starting next week, I won't have much time to get started on any major projects for a while so work space organization will be the plan on record. More specifically, lighting is a still an ongoing task as I'm boosting the amount of Edison for the garage and the studio area.

Well, it's time to get busy. Be safe and always enjoy tinkering!