Braided Cable

We are facing a typical problem while sheathing a braided cable. The cable construction consist of cable core + polyester tape + Al-PET Mylar tape + Drain Wire + ATC Braiding. During sheathing of the braided wire which is about 3.5mm in dia, we are observing that the drain wire is getting protruded from the braid and causing bulge in the sheath. This protrusion is not visible during braiding operation but is visible during sheathing. We have tried with increasing the tension of the drain wire, tension of the pay-off during sheathing but still the problem is persisting every now and then. Pl. suggest any possible corrective action.

Hello Shekhar,

Wow, the drain wire coming through the braid at sheathing! What is your % coverage of the annealed tinned copper braid (ATC). It obviously can't contain the drain which we assume is solid annealed tinned copper wire.

It would seem that the drain wire is being stretched when spooled on the braider take up. Then, when the core is straightened at the pay off at sheathing, there is excess length in the drain wire.

Can you see the drain wire protruding at sheathing before the core enters the crosshead or is it just a bump?

If you are tubing on the jacket:

The excess length in the drain could longitudinally slip along the core, build up and ultimately protrude through the braid. This slipping action could be the result of:

(1) A tight vacuum seal (rubber) as the cable enters the crosshead.
(2) Improper or inadequate support of the core inside the crosshead before entering the tip.
(3) Inadequate clearance in the tip.
(4) A combination of all three above.

If you are using a pressure set-up at sheathing then (2) and (3) above are appropriate.

Here are a few possible solutions:

(1) Use larger cable reels with large drums at braiding to minimize the drain wire stretch.
(2) Apply a stranded drain wire.
(3) Apply the stranded drain wire helically.
(4) Apply a second helical tape over the braid to contain the drain wire.

Let us know how you make out.

Kindest regards,
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

Thanks for the inputs.
The coverage of braid is 65% and the protrusion is observed when the core unwinds from the payoff. I have observed that elongation of the solid ATC drain wire is 20% which may be causing stretching during braiding. It may be appropriate to reduce the elongation % of the drain wire.

Yeah, we are tubing on the jacket and are using a die before the crosshead, so as to flatten any protruding braid wires which were causin sheath faults earlier. I have also changed the payoff from a driven one to a braking payoff so that I can give some tension to the core. Some improvement has been observed but not completely.

Regards

Hi,
Please have a look on your capstan from the braiding machine. If you run a small one ( 500 m or less) maybe here you have a bigger influence as you have from the take-up reel.
Other point is the deflector on the capstan, maybe you damaged the drain wire here.

Best regards
Frank Knobloch
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Dear Frank,

Let me clarify, The drain wire dia is 0.4mm, braiding is being done with 16 x 4 Nos. of 0.15mm wire and the diameter over braid is 3.5mm.

Regards

Sheks