# Cadweld melting wires



## mikeh32 (Feb 16, 2009)

Pictures could help....


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## MHElectric (Oct 14, 2011)

Too much shot? 

Not to be stating the obvious, but did you check what size shot you were using for your mold and wire? If it was too high it will burn right through the wire.


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## mikhen (Jan 11, 2013)

MHElectric said:


> Too much shot?
> 
> Not to be stating the obvious, but did you check what size shot you were using for your mold and wire? If it was too high it will burn right through the wire.



Sorry no pictures. Concrete was waiting to be dumped, no time.
We checked, and checked again. 150plusf20. We even had 2 of the narrower, cone shaped shot with the same number and tried them. results.


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## mikeh32 (Feb 16, 2009)

did you clean the rebar?

and what type of fill was it?


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## mikhen (Jan 11, 2013)

Rebar was clean and preheated. We use the shots with the electronic igniter. they were 150plusf20, which is what was called for.


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## 360max (Jun 10, 2011)




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## mikhen (Jan 11, 2013)

Already saw that, but there was a lot more swearing at my jobsite.


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## piperunner (Aug 22, 2009)

mikhen said:


> Spent a day struggling with Cadwelds. #4 rebar to 4/0 copper. Had the right mold, right shots, everything was cleaned and preheated. It was an onsite electrician, electrical inspector, and myself. The welds would melt the copper wires right off, and when they did form, they would break away from the rebar. Out of 8 locations, we had 1 perfect weld, and we used 2 shots to make them work. Factory rep says the mold wasn't heated. Well we did heat it, and after 20 some shots, it was well heated.
> Anyone have any idea what went wrong?


Well you said in one of your post you were using a 150 load is that correct?

Lets see heat up the mold plus use a wire wheel and clean the rebar without being there myself ill take a guess . The mold is worn out the load is more then you need we use a 90/115 load on 4/0 to a number 5 # rod normally . Check rebar size 
If the rebar is damp or wet it will burn hotter steam pressure .
clean the rebar .
Seal up the bottom and sides with duct seal around wire and rebar . 
The clamp is not tight enough tighten it up .
Most of the time it depends on the rebar cross metal hatching on the surface it can be not letting the gap close all the way so air makes it hotter burns and copper drips out the mold .
We cadweld all the time at our job and i mean everyday rebar steel bonding check you plate maybe someone put another top on it ive seen that done .


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## mikhen (Jan 11, 2013)

Good tips. The mold I had was used on only 4 molds before today. rebar size was verified. We know we used what was called for. It would seem the load was to big. I will check plate info again tomorrow.


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## piperunner (Aug 22, 2009)

mikhen said:


> Good tips. The mold I had was used on only 4 molds before today. rebar size was verified. We know we used what was called for. It would seem the load was to big. I will check plate info again tomorrow.


Well my Erico book say a 150 is fine but we have used a lower charge at times to make it look better and more solid connection due to rebar not being perfect . So lets see what happens try it tell us what happens one thing i do is if the mold tighten and sealed use something to support it better maybe its not closing up have fun .
Never used a bigger load i know this trust me one thing do you clean your mold out each hit .Ive seen the wire move during the hit and screw up the connection support it so it can not move .


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## Celtic (Nov 19, 2007)

It happens sometimes ...not often, but it does...for whatever reason I'll melt a conductor or two every couple of hundred shot.


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## varmit (Apr 19, 2009)

The mold needs to be supported so it is immobile when the shot is lit. If there is the least twitch, the shot can be bad. Also, rebar can be made from some odd junk steel that is not absorbing the heat and causing the wire to take all of the heat from the shot. 

I have had to use a lower heat shot several times to get good welds, but sometimes nothing seems to work. If the wire has been wet, this can cause problems.


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## drsparky (Nov 13, 2008)

I agree with piperunner and varmit, any movment during the shot can cause the problems described.


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## ptcrtn (Mar 14, 2011)

The last company I worked for quit using cadweld and started using Burndy Compression connections.









I got to admit I liked them better than cadwelding


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## HawkShock (Nov 27, 2012)

Wore out mold. Been there. A little duct seal around where the wire exits will save the mold for a little while.


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## mikhen (Jan 11, 2013)

Op here, I did have the molds supported. Maybe the boss bought a used mold. I know it was only used for 4 shots by us before I used it. Thank you everyone for this information.


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## Southeast Power (Jan 18, 2009)

Maybe get clumsy and spill 1/2 the shot powder and see what happens.


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## Sparky208 (Feb 25, 2011)

mikhen said:


> Spent a day struggling with Cadwelds. #4 rebar to 4/0 copper. Had the right mold, right shots, everything was cleaned and preheated. It was an onsite electrician, electrical inspector, and myself. The welds would melt the copper wires right off, and when they did form, they would break away from the rebar. Out of 8 locations, we had 1 perfect weld, and we used 2 shots to make them work. Factory rep says the mold wasn't heated. Well we did heat it, and after 20 some shots, it was well heated.
> Anyone have any idea what went wrong?


I had the same problem. Caddy sells copper shims u wrap around rebar. If u were not using them that could be the problem. I burnt off a bunch of them until I figured it out. When I got the mold it came with 2 of them, their instructions suck. I looked in the book and found them.


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## Marcus (Mar 30, 2010)

360max said:


>


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## mikhen (Jan 11, 2013)

Op here, we were using the copper shims. I tried them on the rebar, on the wire, on both, without any. You name it. It seems the only explanation, and it was one that was mentioned on here, is that the rebar was taking any of the heat. Next time, I will have lower shot with me.


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## varmit (Apr 19, 2009)

Even as violent as the shot firing appears, the the metallurgical bonding properties of a Cadweld shot are designed for a limited range of alloys. Today with most steel being recycled and from third world countries, and since rebar is usually the bottom of the barrel of metal quality, there is no simple way to determine if a Cadweld will work consistently on the material that you are dealing with. I would think that copper recycling, with all of the junk that gets mixed in with the copper scrap, would have a similar effect. I am not against recycling. I am just making an observation.

When Cadwelding works properly, there is no better connection. When it does not work, there are few things more aggravating.


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