Making an ARC Welder - Part 2 of 2
Intro: Making an ARC Welder - Part 2 of 2
How to convert scavenged microwave parts into a useful arc welding machine. This is part 2 of 2, and focuses on the electrical system and finishing touches.
More projects at www.thekingofrandom.com
Before you watch this, make sure you've seen Part 1.
More projects at www.thekingofrandom.com
Before you watch this, make sure you've seen Part 1.
STEP 1: Watch the Video!
WARNING: Stick welding, and/or the modification of a Microwave Oven Transformer (M.O.T), can be very dangerous and presents risks of UV radiation, shock hazards, burns, fires, fumes and a multitude of other risks. This project should not be attempted without a thorough understanding of electricity, adult supervision and adequate training. Misuse, or careless use, of tools or projects may result in serious injury and/or death. Use of this content is at your own risk.
STEP 2: Transformer Platform
I started this part of the project with a scrap piece of 3/4" birch I had left over from my "Router Table" project.
The measurements for the board were 7"x10", and that keeps this about as compact as practical.
I found a piece of 2x2 as well, and screwed it onto the center of the board about an inch from the edge.
Two pilot holes were drilled in the top to accommodate our electrode lugs.
I decided to use lugs here rather than keep it all one continuous cable, because it gives the option of changing out electrode cables, or easily modifying the electrical output for future projects.
The measurements for the board were 7"x10", and that keeps this about as compact as practical.
I found a piece of 2x2 as well, and screwed it onto the center of the board about an inch from the edge.
Two pilot holes were drilled in the top to accommodate our electrode lugs.
I decided to use lugs here rather than keep it all one continuous cable, because it gives the option of changing out electrode cables, or easily modifying the electrical output for future projects.
STEP 3: Making and Crimping Copper Lugs
Copper lugs can be pricy, but I found that if I used a 2" length of 1/2" copper tubing, I could make my own.
I used a bench vise to crimp 1" of the tubing completely flat, then drilled a hole in the flat piece.
A belt sander helped to clean up the edges a bit to make it easier to handle, and make it look a bit nicer as well.
For the electrode cables, I used some of the 8awg cable left over from when we wound the transformer coils.
Next, I exposed the copper on the end of the cable, and bent it over so it would fit inside the lower part of the lug.
I flattened it with a bench vise to make a solid electrical connection, and in my testing, the connection doesn't come apart.
If you don't have a bench vise, I imagine a hammer could work with very similar results.
I used a bench vise to crimp 1" of the tubing completely flat, then drilled a hole in the flat piece.
A belt sander helped to clean up the edges a bit to make it easier to handle, and make it look a bit nicer as well.
For the electrode cables, I used some of the 8awg cable left over from when we wound the transformer coils.
Next, I exposed the copper on the end of the cable, and bent it over so it would fit inside the lower part of the lug.
I flattened it with a bench vise to make a solid electrical connection, and in my testing, the connection doesn't come apart.
If you don't have a bench vise, I imagine a hammer could work with very similar results.
STEP 4: Connecting the Electrodes
Since the system is AC, there really is no "ground" connection and it doesn't really matter which cable connects to which side, but I decided to put a "ground" clamp on the left side, and the electrode holder on the right.
I also spliced the cable between the two transformers and connected them to a common lug so I could have the option to center tap the transformers for future projects, like powering an arc furnace for example.
For the clamp, I found this metal one at the hardware store for only $0.99. When the rubber tips were removed, it could conduct electricity.
I crimped a piece of copper tubing to the wire, then secured the tube to the clamp with a screw. For being so cheap, the clamp had a surprising amount of clamping force, which was great for biting onto the workpiece.
I bought a replacement electrode holder for $13 rather than making my own. It looked better and was much more practical for welding with.
I also spliced the cable between the two transformers and connected them to a common lug so I could have the option to center tap the transformers for future projects, like powering an arc furnace for example.
For the clamp, I found this metal one at the hardware store for only $0.99. When the rubber tips were removed, it could conduct electricity.
I crimped a piece of copper tubing to the wire, then secured the tube to the clamp with a screw. For being so cheap, the clamp had a surprising amount of clamping force, which was great for biting onto the workpiece.
I bought a replacement electrode holder for $13 rather than making my own. It looked better and was much more practical for welding with.
STEP 5: Wiring the Electrical System
I used one of the cords saved from one of the microwaves and cut off the green wire.
I secured the cable to the wood base to prevent the cables from pulling off the connections.
The black cable connects to one of the primary terminals on one of the transformers, and the white wire connects to one of the other transformers primaries. It doesn't really matter which one.
I used another piece of wire to connect the other 2 posts together, essentially connecting the 2 transformers in series.
Later on, when the device is tested, the two electrodes should be outputting around 36 volts. If you're seeing very low voltage, like 2.4 in my case, that means the transformers are canceling each other out, and this can be fixed by just switching the connections on one of the transformers.
I went ahead and did that and ended up with about 37 volts between my ground clip and electrode holder.
I secured the cable to the wood base to prevent the cables from pulling off the connections.
The black cable connects to one of the primary terminals on one of the transformers, and the white wire connects to one of the other transformers primaries. It doesn't really matter which one.
I used another piece of wire to connect the other 2 posts together, essentially connecting the 2 transformers in series.
Later on, when the device is tested, the two electrodes should be outputting around 36 volts. If you're seeing very low voltage, like 2.4 in my case, that means the transformers are canceling each other out, and this can be fixed by just switching the connections on one of the transformers.
I went ahead and did that and ended up with about 37 volts between my ground clip and electrode holder.
STEP 6: 240 VAC
I needed 240 volts AC to power this system, so I used 2 plugs, a connector, and some 10awg wire.
Each of the outlets in my house output around 120 VAC, and the circuits all connect back to the breaker bus bars. There are 2 busses, and I learned that if I took a hot line from each bus, the electrical potential between them was 240 VAC.
Rather than tapping into the breaker box directly, I used extension cords and connected to 2 different outlets that were 180 out of phase (on separate bus bars).
When they were connected to my adaptor, the result was 240 VAC.
It's important to keep in mind that this welder doesn't have an on/off switch, and no current limiting of it's own. That's why I had to build a separate power controller I call the "Scariac". It's like a "Variac" except much more dangerous. But it is pretty cheap, and it gets the job done.
Look for how to build the Scariac in a different project.
Each of the outlets in my house output around 120 VAC, and the circuits all connect back to the breaker bus bars. There are 2 busses, and I learned that if I took a hot line from each bus, the electrical potential between them was 240 VAC.
Rather than tapping into the breaker box directly, I used extension cords and connected to 2 different outlets that were 180 out of phase (on separate bus bars).
When they were connected to my adaptor, the result was 240 VAC.
It's important to keep in mind that this welder doesn't have an on/off switch, and no current limiting of it's own. That's why I had to build a separate power controller I call the "Scariac". It's like a "Variac" except much more dangerous. But it is pretty cheap, and it gets the job done.
Look for how to build the Scariac in a different project.
STEP 7: Setting the Current
To set the current for welding 1/16th rods, I connected the ground clamp and electrode holder together, effectively shorting out the system. The Scariac has a loop of wire built in that allows me to monitor the primary current, and when it's set to about 15.5 amps on the primary, it gives me around 100 amps on the secondary.
Cranking up the power on the Scariac can get the welding cables up over 200 amps, but I really don't recommend running them that high for more than a few seconds or the plastic coating on the cables will overheat and may start melting.
In any case, you can see there is certainly enough power for welding.
I burned ten 1/16 rods in a row, and the system was only warm to the touch. This gives me the impression it's got a pretty good duty cycle for use with the smaller rods, and these are probably the only one's I'll really need for my hobby use anyway.
Cranking up the power on the Scariac can get the welding cables up over 200 amps, but I really don't recommend running them that high for more than a few seconds or the plastic coating on the cables will overheat and may start melting.
In any case, you can see there is certainly enough power for welding.
I burned ten 1/16 rods in a row, and the system was only warm to the touch. This gives me the impression it's got a pretty good duty cycle for use with the smaller rods, and these are probably the only one's I'll really need for my hobby use anyway.
STEP 8: Finishing Touches
Rather than leaving all the terminals exposed, I picked up a plastic container, painted it black, and drilled a few holes for the cables.
I used the top as the base, and the bottom as the top. It seemed to work pretty well.
There are also ventilation holes cut in the sides to allow airflow over the coils, and even consideration made for attaching a fan to blow cool air and help regulate the temperature while welding.
At this point, the system is completely finished and ready for welding!
You can see some of my first few experiences with the world of welding by clicking here.
I used the top as the base, and the bottom as the top. It seemed to work pretty well.
There are also ventilation holes cut in the sides to allow airflow over the coils, and even consideration made for attaching a fan to blow cool air and help regulate the temperature while welding.
At this point, the system is completely finished and ready for welding!
You can see some of my first few experiences with the world of welding by clicking here.
STEP 9: All Finished!
Well, there you have it! A homemade AC stick welder.
If you haven't see the video yet, it's not too late. Watch it here!
If you like this project perhaps you'll like some of my others. Check them out at www.thekingofrandom.com
If you haven't see the video yet, it's not too late. Watch it here!
If you like this project perhaps you'll like some of my others. Check them out at www.thekingofrandom.com
12 Comments
4DIYers 7 years ago
Wow that is quite impressive! I have experience in welding, those welds have definitely penetrated well and seem very clean. The overheating is quite normal on any welder, depending on their design, they have duty cycles. So they can only run for a certain period of time, then need a certain period to cool down. I would definitely like to see a variable controller added so you don't have to worry about burning through lighter gauge metal.
rust weems 8 years ago
Hello. Kudos on your brilliant instructable. I am currently rounding up the parts for my own build. A problem that I encountered is that people are not very big on microwaves where I live, so they are near impossible to come by. Are there any alternatives to salvage the transformers from?
Thank you.
Di Immortales 9 years ago
do you know where a good place to get microwaves are because I dont know where to get one
Zenoah1 10 years ago
I live in europe so we have 230/240 from our outlets, would it be possible to use just one MOT? or would the load on one MOT burn out way to quickly?
Jb
turtledrake 10 years ago
I'm just a little confused on this section here. Why can't you simply plug each transformer into an outlet individually?
Thanks
Evan
sconner1 11 years ago
Instead of wiring the primaries in series and risking one's home with very sketchy and easily mistaken connections, Simply make sure your windings are in phase with each other and wire the primaries in parallel at 120V and leave the secondaries in series. This should accomplish the same voltage without using the dangerous 2 outlet hack although this limits your amperage draw to 15 or 20A. OR wire up a proper connection to the 30 or 50A dryer or stove outlet. And for God's sake, Put fuses in your electrical primary circuits! Another good practice is to put the rig in a metal box and connect that safety ground wire to it. Be safe out there.
sconner1 11 years ago
The 3 prong dryer outlet has the 2 hots and ground.
A 4 prong stove outlet has 2 hots, a neutral (center tap) and ground.
matokage 11 years ago
sscsnake 11 years ago
eleechapin 11 years ago
Bobblehead Einstein 11 years ago
pfred2 11 years ago