Technical info on spot welding?

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SamTexas

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I have read both threads on home made and reasonably priced spot welding machines. But I could not find the working technical aspect for them. The following questions are specific to spot welding small cylindrical battery cells (18650 and 26650).

1) What is the optimal voltage at the tip of the electrodes? 3V, 5V, or what?
2) What is the optimal current? 50A, 100A, or what?
3) What is the optimal time for the above two? 0.5 second, 1 seconds, 2 seconds, or what?
4) What is the optimal distance between the 2 electrode? 2mm, 3mm?

I looked up in Wikipedia too, but could not find any specific values.
http://en.wikipedia.org/wiki/Spot_welding

Thanks.
 
Will be interesting to see what info we can all find out

I have been thinking about building a Capacitive Discharge Spot Welder.
I used to be quite into my car audio systems a number of years back, and I still have a few car audio capacitors, the biggest one I have is 3.5 farad and rated upto 20volts (24volts surge) with an ESR of 0.00195 Ohms .

12volts = 252 Joules.
16volts = 488 Joules.
20volts = 700 Joules.
24volts = 1008 Joules.
 
Hi,

I was at a friend's house a few weeks ago and spot-welded a 13s9p Sony battery with a spotwelder that he built himself.
I've also talked with some people about making a capacitive spot welder.

If you just want to build something that works and isn't too flashy, go with this:

2* 10mm diameter copper electrodes
12V car battery or 3s5p-10p old power tool cells
25mm² wire
12V PSU (to recharge)
NE555
Mosfet driver
5-6 Mosfets (low voltage, low RDSon, HIGH current)
Footswitch

With a setup like that I've successfully made several hundred spots. It's a lot cheaper than fiddling around with capacitors that are most likely not up to the job anyways.
 
I'm looking into getting four malectric, open source car battery powered spot welders.

More info on them here: https://malectrics.eu/product-category/arduino-spot-welder/

They have an "auto pulse" mode where they automatically fire a set time after an electrical connection is sensed. I need more current than just one of these things can handle, enough to weld .01" copper.

I'm intending to connect each of the four leads of the four spot welders to a common tungsten tip and run them in parallel for 4x the current.

Is this a terrible idea? My gut tells me yes but I can't think of a physical reason for why it won't work. :D

If you can explain the physical reason for why this is a terrible idea let me know.
 
Occam's Laser said:
I'm looking into getting four malectric, open source car battery powered spot welders.

More info on them here: https://malectrics.eu/product-category/arduino-spot-welder/

They have an "auto pulse" mode where they automatically fire a set time after an electrical connection is sensed. I need more current than just one of these things can handle, enough to weld .01" copper.

I'm intending to connect each of the four leads of the four spot welders to a common tungsten tip and run them in parallel for 4x the current.

Is this a terrible idea? My gut tells me yes but I can't think of a physical reason for why it won't work. :D

If you can explain the physical reason for why this is a terrible idea let me know.
Click to expand...

I bought Aulakiria's LiPo based spot welder, he has tested 0.20mm nickel with no issues. I'm still waiting for the foot pedal to show up from eBay though. That said, neither of these devices are intended to spot weld thick copper (0.25mm). One of the main things people mention in a thread I pasted below, is that at the energy levels required to spot weld that thick of copper, you can potentially damage the battery cell.

Here is a thread where they are discussing copper https://endless-sphere.com/forums/viewtopic.php?f=14&t=84680&start=125
 
Hey Sam
Here are my answers to your qs, not by any stretch the only answers. Too many variables without more details but anyway..
For my AC single pulse spotwelder...
1) depends but btw 2v and 20v. Most AC welders would be about 2-4v I use 6v. Cd welders are variable.
2) depends but about 800-1000a min. I'm at about 1500, stronger units do 2ka or more.
3) depends on the above two, and what you're welding. My AC wave form requires longer pulses at 20-80ms. DC current spotwelder are shorter like 5-30ms or something- don't really know cause I'm not using one.
4) between 2-8mm I'd say. But you can do wider, it's just not usually necessary.

Short and sharp and hot is the go :shock:
All ball park figures ottomh-not necessarily optimum. :wink:
 
kdog said:
Hey Sam
Here are my answers to your qs, not by any stretch the only answers. Too many variables without more details but anyway..
For my AC single pulse spotwelder...
1) depends but btw 2v and 20v. Most AC welders would be about 2-4v I use 6v. Cd welders are variable.
2) depends but about 800-1000a min. I'm at about 1500, stronger units do 2ka or more.
3) depends on the above two, and what you're welding. My AC wave form requires longer pulses at 20-80ms. DC current spotwelder are shorter like 5-30ms or something- don't really know cause I'm not using one.
4) between 2-8mm I'd say. But you can do wider, it's just not usually necessary.

Short and sharp and hot is the go :shock:
All ball park figures ottomh-not necessarily optimum. :wink:
Click to expand...

Sams post was from 4 years ago.
 
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