Micro spot welder ?

[Javert]

I will need to spot weld 0.5mm Cu wire to 0.5mm brass sheet and 1mm brass wire. Approx. 200 pieces per day, and so I'm thinking about a suitable spot welder or its construction.
I'm interested in this as a reference piece, the price is insane.
Parameters
OUTPUT VOLTAGE RANGE 0.10-5.00 V (0.01 V Intervals)
OUTPUT CURRENT RANGE 10.0-250 A
OUTPUT POWER RANGE 1.0-650 W
WELD TIME (EACH PULSE) 1-500 ms (1 ms intervals)

After 30 seconds of thinking, I came up with this solution.
Please don't laugh, I present it as food for thought for someone who deals with this issue further.

I'll take a 2.7V 3000F capacitor any as this and this , 4pcs (may be 6 or 8) serial and paralle (5,4V battery) connected directly to the copper strip 20x3mm.
I will use a MOSFET as a switching element on the low side, too direct connect to copper strip, any as IXTN660N04T4 40V 660A 0.85mOhm
I charge the capacitors with a voltage of 100mV to 5.4V and then the MCU turns on the MOSFET for the set time and blows for 1 to x00ms.
Is this very stupid?

 

[dick_freebird]

An additional point - the welding electrode, if you mean to spot-weld,
must not want to weld to copper. Copper tongs on my spot welder are
OK for steel (the intended use) but would self-weld to copper workpieces
no doubt. Maybe flip the script and put a thin steel cap on whatever you
use for the electrodes.

Re brazing - you could also use OA torch for brass braze or you could
use readily available, cheap torch MAPP gas to do silver-solder (a braze)
or that copper-phosphorus rod they sell at hardware stores for A/C
tubing / fittings. If you don't happen to have a 700C oven / kiln handy.

 

[D.A.(Tony)Stewart]

You will need to distribute the heat such that they all reach melting temperatures in sufficient time without spattering.

 

[KlausST]

You will need to distribute the heat

My idea was the opposite: not to distribute the heat, but to focus the heat .. to the welding point.

I see it like a heatsink: It distributes heat. The result is; lower temperature or more power to dissipate.
But for welding I want high temperature for the metal to melt, and a don´t want to use more power than necessary.

Maybe I misunderstood ...

Klaus

 

[D.A.(Tony)Stewart]

My idea was the opposite: not to distribute the heat, but to focus the heat .. to the welding point.

I see it like a heatsink: It distributes heat. The result is; lower temperature or more power to dissipate.
But for welding I want high temperature for the metal to melt, and a don´t want to use more power than necessary.

Maybe I misunderstood ...

Klaus

This is a 3D problem, but I was thinking of the normal axis or vertical plane of dissimilar materials.. The electrical and thermal resistance of wires and sheet will have different energy levels to reach and achieve uniform melting to fuse together well in the vertical axis as well as spread enough width from the brass and Cu wires to the sheet which will act as a heat sink and not melt easily. Perhaps each wire can be done separately. But the wire will splatter easily before the sheet heats up. Thus high insulated pressure is needed from the electrode to thermally couple the materials during fusion. Normally on batteries they use ultrasonic "cold welds" also used in crystals. But those are expensive when high power.