How do you ensure you are getting a cold weld in a crimp?

FilterGuy · Feb 10, 2022

Does anyone know a good test to ensure a crimping process is creating a good cold-weld? I have always used a crimper and just assumed I was getting a good crimp. I have also cut a few crimps in half to check that it looks like solid copper. However, is that sufficient? Is there something else that can be done to verify a cold weld was achieved?

I am working on some stuff right now that uses some non-standard crimping and I am wondering if there is a good way to verify the process? (Destructive testing is OK).

Roswell Bob · Feb 10, 2022

Pull Test?

Roswell Bob · Feb 10, 2022

There are ring terminals on the arresting cables to catch aircraft on the aircraft carrier. They use hydraulic press to put them on.

https://www.creare.com/wp-content/uploads/2019/08/Creare_CSM_Case_Study_Aug2019.pdf

FilterGuy · Feb 10, 2022

Roswell Bob said:
Pull Test?

A failed pull test would certainly tell you there was a problem with the crimp..... but if it does not pull apart does it tell you it was a cold weld?

upnorthandpersonal · Feb 10, 2022

Neutron imaging:

(PDF) Investigation of microstructure within metal welds by energy resolved neutron imaging

PDF | The recent development of bright pulsed neutron sources and high resolution neutron counting detectors enables simultaneous acquisition of a... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

US3612874A - Neutron radiography of weld joints - Google Patents

A nondestructive neutron radiographic technique capable of producing improved radiographs of weld joints is disclosed. Lack of contrast in neutron radiographs of two pieces which have been welded together makes resolving fine gaps in the weld difficult. In the disclosed system, one of the two...

patents.google.com

FilterGuy · Feb 10, 2022

upnorthandpersonal said:
Neutron imaging:

(PDF) Investigation of microstructure within metal welds by energy resolved neutron imaging

PDF | The recent development of bright pulsed neutron sources and high resolution neutron counting detectors enables simultaneous acquisition of a... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

US3612874A - Neutron radiography of weld joints - Google Patents

A nondestructive neutron radiographic technique capable of producing improved radiographs of weld joints is disclosed. Lack of contrast in neutron radiographs of two pieces which have been welded together makes resolving fine gaps in the weld difficult. In the disclosed system, one of the two...

patents.google.com

I love excuses to buy tools but that is a stretch.... I don't think I could sneak a Neutron Imaging system past my wife!! ?

upnorthandpersonal · Feb 10, 2022

FilterGuy said:
I love excuses to buy tools but that is a stretch.... I don't think I could sneak a Neutron Imaging system past my wife!! ?

I have one at my lab

ArkRob · Feb 10, 2022

Just send a really big current through it.......

HighTechLab · Feb 10, 2022

ArkRob said:
Just send a really big current through it.......

How does a really big current determine if a cold weld has been made or not?

I have 450A @ 8v on speed dial, but not sure if I could put it to use to quantify the question here.

Ampster · Feb 10, 2022

HighTechLab said:
How does a really big current determine if a cold weld has been made or not?

It heats up if it not good.

FilterGuy · Feb 10, 2022

ArkRob said:
Just send a really big current through it.......

That is kinda my fall-back plan. Try it under load and see how well it works...

upnorthandpersonal · Feb 10, 2022

HighTechLab said:
How does a really big current determine if a cold weld has been made or not?

I have 450A @ 8v on speed dial, but not sure if I could put it to use to quantify the question here.

You could measure the voltage drop over it. A failed cold weld has worse current carrying properties than a good one. Temperature profile at the same currents will also be different.

Edit: https://media.digikey.com/pdf/data sheets/molex pdfs/tbo quality crimp handbook.pdf

RCinFLA · Feb 10, 2022

Sacrifice a sample piece of wire and lug. Hack saw it through crimp. It will look close to a solid piece of copper.

This assumes you have a quality crimper that is consistently repeatable.

You would be surprised how much resistance there is where the lug tube necks down from end of wire to flat of lug. Keep away from cheap thin wall gauge metal lugs.

timselectric · Feb 10, 2022

In my marine connection days. We always crimped and soldered. (Flux applied to lug, before crimping)
The solder, also blocked contamination ingress.

MrM1 · Feb 10, 2022

If using a hydrolic crimper you could make 3 or 4 cables and lugs at different pressure rates, one being your desires pressure and the others less. Then test for voltage drop on each to get a baseline. Then cut them each open to see how they look. If your target pressure looks good then u'd have some idea of a good and questionable voltage drop.

FilterGuy · Feb 10, 2022

timselectric said:
In my marine connection days. We always crimped and soldered. (Flux applied to lug, before crimping)

This always brings up near-religious debate..... Some folks really think soldering is a bad idea. I have mixed thoughts on it.... I lean toward thinking it is a good idea. The one thing folks have mentioned that makes me wonder is that the solder will wick up the wire. At the end of the solder creates a spot that could be prone to stress wear..... I don't know if this is a big deal or not.

SparkyJJO · Feb 10, 2022

Yes, but if it is stationary there should be no issue.

MrM1 · Feb 10, 2022

FilterGuy said:
This always brings up near-religious debate..... Some folks really think soldering is a bad idea. I have mixed thoughts on it.... I lean toward thinking it is a good idea. The one thing folks have mentioned that makes me wonder is that the solder will wick up the wire. At the end of the solder creates a spot that could be prone to stress wear..... I don't know if this is a big deal or not.

Off grid garage Andy (take it with a grain of salt YMMV) says solder is not good. Creates a second connection point (so to speak) for failure inside the lug

timselectric · Feb 10, 2022

Apply heat to the bottom of the lug, and only Apply just enough solder to fill the lug. I never had a wicking problem. If anyone did, the connection was remade.
These were high vibration installations.

timselectric · Feb 10, 2022

Also, solder wasn't used for every connection.
Only if it was going to be in a high moisture environment.

curiouscarbon · Feb 10, 2022

timselectric said:
Apply heat to the bottom of the lug, and only Apply just enough solder to fill the lug. I never had a wicking problem. If anyone did, the connection was remade.
These were high vibration installations.

if soldering crimped lug, this is how i would try. the environments i'm building for are not high moisture

soldering kind of like art; applying heat to opposite side of lug, ensures the solder will wick in the desired direction (into the lug)

heating the conducting wire, might be more likely to cause excessive wicking.

i'm ignorant of exactly how to do it, so i rely on a crimp tool with long arms for good leverage.

this makes me want to try out what @MrM1 mentioned

MrM1 said:
If using a hydrolic crimper you could make 3 or 4 cables and lugs at different pressure rates, one being your desires pressure and the others less. Then test for voltage drop on each to get a baseline. Then cut them each open to see how they look. If your target pressure looks good then u'd have some idea of a good and questionable voltage drop.

or at least, perhaps test large cables like this at least once after crimping, and perhaps redo if resistance comes back higher than expected.

RCinFLA · Feb 10, 2022

I used to solder my 2/0 lugs on. I used Excelene welding cable as the insulation can take the heat.

Hedges · Feb 10, 2022

Hermeticity test?
Gross leak: connect a hose to it, pressurize and immerse in water (only useful if your terminals don't have closed-toe shoes; if they do, drill a vent hole in the toe.)

If you want to do fine leak, that typically involves helium and an atomic mass spectrometer, or radioactive isotopes.
So I suggest you stop at gross leak.

FilterGuy · Feb 10, 2022

timselectric said:
Also, solder wasn't used for every connection.
Only if it was going to be in a high moisture environment.

Yes.... that is one of the reasons I like solder. It fills any void and helps prevent corrosion.

Roswell Bob · Feb 11, 2022

upnorthandpersonal said:
I have one at my lab

Throughout the years I have always asked for a SEM, scanning electron microscope when it came time for budgeting test equipment for the upcoming year. It was more of a joke than anything real. When I got to Creare and asked for one, I was told, "We don't need another one." It was an amazing place overun with PHDs.

How do you ensure you are getting a cold weld in a crimp?

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