Tin Plated cable

Hello Dear Forum,

Hope all of you are doing well!!

I have been experimenting a lot of issues with one of my applications and it's based on Tin plated core 7 and 19 strands used with a Polyethylene Low Density compound, there are two conditions:

1.- One of my customers has an application that needs cable cut at 150mm (About 5.9 inches! ) in length and when he uses my cable the insulation creeps. (It retracts 2 mm)

2.- I cannot run this specification at more than 400 meters/min ( 1312 Feet per minute) due a lot of core breaks and quality issues as there are lumps/bumps on the cable as well as sparks. Same when I irradiated it..I cannot go faster than 400 meters/min because the same condition.

my general process conditions are:

- 80 mm Extruder 24:1
- Cooling water first 5 meters at 60 C remainder at 27 C
- Temperature profile from 130 C to 160 C
- Maddock barrier type mixing screw
- Tooling with compression design ( 60 Degrees)
- Irradiation dosage 7.5Mrad
- Compound density 1.42

Any suggestion or advice to improve this condition will be greatly appreciated!!!

regards,

Hello There Martin,

Well you certainly have a lot of technical issues but they can be easily fixed.

First I imagine that you are using hot dipped tin on the strands. This is done by dipping the copper strands in a bath of molten tin and when they exit, and the tin is solid, sizing them with a carbide drawing die. (Sometimes with water as a lubricant.) Then the strands are stranded in the same way as a non-tinned copper conductor. Now you have a standard tin coated wire size but it is certainly not as smooth as electroplated tinned wire.

Preheating of the conductor at extrusion can be done but there must be great caution so that the tin is not softened or melted. This will give tin build-up and wire breaks in the extruder tip. That can be your source of lumps, bumps and wire breaks. Examination of the breaks, lumps and bumps will give you the answers,

Your cold water cooling trough temperature seems pretty warm to me at 27C (81F) I would prefer to see this in the 10C (50F) to 15 C (59F) range.

Now you go to the cross-linking by the radiation unit and my major concern is that the tin does not melt during this process. You will have to walk a fine line to obtain complete cross-linking with no melting of the tin. (Strands melted together.) Likewise you have to be sure you are not stretching the wire when it is crosslinked.

Just some careful process engineering will resolve your issues.

You should have no shrink back now and the only other concern is that your customer is stretching the wire when it is cut into the short lengths.. That will also produce shrinkback. .

.