DIY Spot Welder




Introduction: DIY Spot Welder

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The new project of make it extreme is the transformation of an old microwave oven into a brand new spot welder. How did we manage that? Firstly, we decomposed the microwave oven and took its transformer and the fan that cools it. The particular project was planned not to make a portable spot welder but one with a stable basis.

Step 1: Metallic Frame - Transformer - Copper Cable

Therefore, we made a metallic frame with a stable basis to support it and we also made some holes on it in order to be able to be screwed on the spot where it will be located. After that, we removed the one copper coil of the transformer and we passed a single coil of a copper cable through the frame, 16mm thick in order to reduce the volt and increase the ampere. Regarding the edges of the cable, we made two copper spikes 25mm of thickness. Then, we placed the cables with the transformer on the metallic frame and after that, we put the spikes on two calipers. The one caliper that is located on the frame remains still while the caliper which is on the upper side opens and closes by just a simple touch on a stepper that we placed on the basis of our machine. Thus, by just stepping on this stepper the calipers close and come together enabling the electricity to permeate the spikes.

Additionally, a spring was placed on the moveable caliper that brings it back to its original position when we release the stepper. To regulate the pressure between the spikes, we placed a mechanism with a spring on our stepper that keeps the stepper moving even if the spikes come together.

Step 2: Control Panel

On the upper side of our machine we placed the control panel that regulates the thickness of the pieces of the iron plate that we need to glue together. On the control panel, we made a timer relay switch that defines the time needed for the weld and as it is commonly known when we glue thicker objects more time is required. Therefore, we have the potential to define the time needed according to the thickness of the material that we glue aiming to the desired outcome. Beside the timer, there are also two indicative lights and a switch on the control panel. When the stepper of our machine is not pressed, then the red light is pressed indicating the machine is not ready to start the weld. However, when we press the stepper and the light is not red anymore but becomes green, we know that it is ready to start the weld. Starting the weld and pressing the stepper, electricity permeates the spikes as well as the metal sheets that we need to glue within the time period that is set.

Step 3: Video

Therefore, the weld is carried out through a safe, controlled procedure. Moreover, the fan that we took from the microwave oven and we placed it behind the transformer keeps the transformer’s temperature low enabling us during the weld process to carry on gluing endlessly.



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    28 Discussions

    Could you supply me with measurements. Love this spot welder. Great job.

    Very nice! Especially the part of the vid showing the rework of the transformer's secondary - super simple! Maybe I'll make something similar from alu extrusions without a welding machine...

    Very nice! Especially the part of the vid showing the rework of the transformer's secondary - super simple! Maybe I'll make something similar from alu extrusions without a welding machine...

    Very nice! Especially the part of the vid showing the rework of the transformer's secondary - super simple! Maybe I'll make something similar from alu extrusions without a welding machine...

    Hey man, this project is amazing, I had seen it on youtube. I'm feel much like make one too. Please post more instructions about electrical thing, and the control panel.


    Excellent piece of fabrication!

    Do you have any idea of what sorts of amperage you're getting from that transformer?

    4 replies

    For a 1000 W transformer I'd estimate easily a few hundred amps. (Hard to be precise with knowing the turns ratio.)

    Turbo, it's a bit more complicated. If you're drawing 8.3 A at 120 V, then you must understand that this is at the primary part of the transformer. The interesting bit is how much will you get from the secondary windings? The whole idea with a transformer in this setup is to lower the voltage, and increase the amps.... So basically, there are 2 ways of finding out: You can measure the voltage during a welding cycle, and apply Ohms law, or you can do it the easy way, using an Amp-meter, such as a clamp- meter. I was interested in the welding current, as this is what tells you what the welder can do.... And for the nerds ;o) I know fully well this is AC, and that you should take cos phi into consideration as well, but I'm not interested in a figure with 8 decimals ;o)

    Thanxx for the answer. I fully understand that it can be hard to eyeball the power. I was hoping that such a sophisticated fabricator as yourself might have a clamp meter. Couple of 100's is not bad at all, obviously theres a long way to industrial 14 kA, but I'm sure you can get away with some pretty weldings....

    I understand the comments that say it is not DIY. This is very good, but for those of us who don't know enough about electronics, some more instruction on how to hook up the wires to the transformer and controls would be appreciated.

    Has anyone any idea's for converting this to weld small band saw blades, either side-on, (as in brazing), or end to end !

    Hi there! Again, it is pretty nice ... But I am also an engineer. However I do not have all these pretty nice stuff you have. So, it is absolutely unusable for me ;( Have you got another _usable_ life-work-hacks?

    2 replies

    If it is unusable for you simply dont say anything...

    Its a very nice and well done point welder!

    2 years ago

    Wow super job!!! Only thing I would add is a dual pulse control that can be varied.

    Very cool build, plus the video was extremely well-done, showing all the key points at a quick pace without any slow, dragging, unnecessary segments.

    Might I ask what kind of welder you were using for the metal parts? Like MIG or TIG or whatever? That's something I'd like to get into but I'm not sure where to start.

    Hi there! When you make a welder bu welding... What does it mean? Do you sell these?

    Thanks for the comment.
    You are a REAL PRO!