Frequently Asked Questions (FAQ)
Frequently Asked Questions:
Can I resistance weld copper? How about projection welding copper?
I’ll start off by saying; projection welding with copper is at least on the fringe of, possibly outside of, the capabilities of the spot welding process.
Resistance welding copper alone is considered impractical, and may only work under special conditions. Projection welding copper, I have never seen anyone do that successfully in a production setting. It’s just not a good fit for this process.
With that said, if you quoted a job and are stuck with it, here are a few comments that might get you through it:
- you should use some higher resistance electrode to touch your copper part. You could use a Tungsten-copper alloy, like “Elkonite” (trade name), you could use pure Tungsten or molybdenum, or we’ve seen some success with carbon/graphite. Elkonite and Tungsten are most readily available, the others would be experimental. Welding copper with copper won’t work.
- you should clamp one of your parts with the machine in “no weld” (the weld turned off), and see if you’re squishing the projections before you even weld. If so, back the pressure off until you’re not squishing projections, and then back it off a little more.
- unless your customer forbids it, try ditching the weld projections and just trying one weld at a time
- the more common and “better” way to use a resistance welder to join copper is to resistance braze with braze foil between the copper parts. Again, if the customer says you can’t do that, then you can’t. I can’t imagine braze foil working well with weld projections, but you could try a few.
- the best solution would be to ditch the projections, use braze foil, and probably do one weld (one side, in your case?) at a time.
This is not a standard application, you will need some time and some iterations to get something shippable.
If you’d like quotes on Tungsten alloys or pure Tungsten, let me know the sizes that you need. There are electrodes you can buy that have a Tungsten alloy brazed to the weld face. Here’s one example: https://www.tuffaloy.
~CK
When I press the foot pedal on my spot welder, sometimes it works and sometimes it doesn’t.
It is a somewhat common occurance that the foot pedal, after some years of being kicked and moved, develops a short in the cable. We have seen it where the cable “nearly” fails, but there are just enough strands of wire left to iluminate the LED (but not enough amps to pull the solenoid closed on the air valve).
Based on your problem being sporadic, we suspect the foot pedal cord has a short. This typically happens down near the foot pedal itself, where the SO cord enters the foot pedal.
A robust solution would be to replace the whole SO cord.
A simpler solution would be to cut off 6″ or so of the cord down by the foot pedal and see if that fixes the problem.
If that fixes the problem and you want to prevent this from happening again soon, you can do various things to prevent the cord from getting kinked in the first place. Some people mount the switches to a plate, some mount to the floor, some put 90-degree cord adaptors at the foot switch.
Please try repairing the cord and let us know if that fixes the problem.
~CK
My spot welder had a major blow out today, now my operators are afraid of the machine.
A resistance weld “blow out” (also called expulsion) occurs when molten metal is forcibly ejected from the weld nugget during the welding process. Here are the main causes:
Excessive Heat Input
- Too high welding current for the material thickness
- Weld time that’s too long
- Insufficient electrode force allowing the heat to concentrate rather than being contained
Poor Electrode Force
- Inadequate clamping pressure fails to contain the molten metal
- As the metal melts, it needs sufficient force to keep it confined between the electrodes
- Force that’s too low can’t counteract the internal pressure from rapid heating
- Pneumatic system (air cylinder) “bottoming out” due to poor tooling and electrode configuration
Contaminated Surfaces
- Oil, rust, scale, or coatings on the metal surfaces create resistance variations
- This causes localized overheating and uneven current distribution
- The contamination can vaporize and create pressure that expels molten metal
Electrode Condition
- Worn, pitted, or misaligned electrodes
- Improper electrode geometry or face diameter
- Contaminated electrode surfaces reducing contact area
Material Issues
- Excessive gap between workpieces
- Material thickness variations
- High-conductivity materials requiring very high currents
Process Parameter Imbalance
- Current ramping up too quickly (insufficient squeeze time)
- Incorrect balance between current, time, and force for the specific material
The key is achieving the right balance: enough heat to create a proper weld nugget, but with sufficient electrode force and proper timing to contain the molten metal until it solidifies. Blow outs typically indicate the process parameters need adjustment or that surface/equipment preparation is inadequate.
~CK
