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If you have a question regarding coaxial, telephone, and building wire, power cable, insulation, extrusion, bunching, stranding, braiding, etc. post it here.
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TOPIC: High strands and min wall

High strands and min wall 5 years 10 months ago #348


We are experiencing minimum wall issues at extrusion and high strands in the core. The compound that we are using is PPE, this compound characteristic is very hard.

Is it recommended to put an check die before the cross head? What is the line tension and screw speed for this material?

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Re: High strands and min wall 5 years 10 months ago #349


"PPE stands for polyphenylene ether, a polymer characterized by regular, closely spaced phenyl groups.

Alloys, or blends of PPE and polystyrene in various proportions, are marketed under the trade names of Noryl and Prevex (General Electric). The resins are processed by conventional injection molding,extruding, and thermoforming methods. Structural foam parts are processed in standard foam molding systems, using either direct induction of nitrogen gas or conventional chemical-blowing agents.

Polyphenylene ether is produced by a process based on oxidative coupling of phenolic monomers. The result, a resin that has good mechanical stability, is then blended with polystyrene to improve processibility. Available grades of molding resins, including glass-reinforced and platabie compounds and heat-resistant grades (containing nylon), in addition to extrusion and foarnable grades. All resins can be furnished in a wide range of colors.

Properties: Polyphenylene ether blends are characterized by outstanding dimensional stability, the lowest water absorption of the engineering thermoplastics, broad temperature ranges, excellent mechanical and thermal properties, and excellent dielectric properties over a wide range of frequencies and temperatures. Several injection-molding and extrusion grades are rated UL 94V-1, or V-0, including glass-reinforced versions. Foarnable grades have service-temperature ratings of up to 205°F in 1/4-in. sections.

Because of their excellent hydrolytic stability, both at room and elevated temperatures, PPE blend parts can be repeatedly steam-sterilized with no significant change in properties. In exposure to aqueous environments, dimensional changes are low and predictable. Resistance to acids, bases, and detergents is excellent. The material is attacked, however, by many halogenated or aromatic hydrocarbons. Prototype testing of components requiring exposure to such environments is recommended."

Source Machine Design

Peter J. Stewart-Hay (WAI Forums Moderator)
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Re: High strands and min wall 5 years 10 months ago #350

Hello xzfxhg,

Extrusion of PPE

First off, it is impossible for us to tell you anything about your extrusion process because we have no idea of which alloy or blend of PPE you are using as well as the complete extrusion conditions including such items as such as metal type, conductor size, extruder size, line speed and so on. Instead you should be discussing these questions with your compound supplier's and extruder supplier's technical or laboratory people. We cannot see what you see and think is obvious! Conductor tension cannot be discussed because as above, we know nothing!

High Strands in the Conductor

The use of a die before the extruder cross head is generally not recommended because one of the strands could break in the die, bunch up into what is called a "birds nest" and break the conductor. Depending on the line speed, this can happen in a fraction of a second and can be very dangerous to anyone nearby.

Instead, your problem is at stranding and this is where your investigation must start. Look for unequal tensions on the pay-offs and, if a double twist machine, make absolutely sure the tensions are all the same in each of the strands in each of the layers. The strands in each layer should be equal but not necessarily the same tension as other layers. Likewise read your manual for your double twist strander and talk with their technical people about recommended individual strand tensions in each layer!

Peter J. Stewart-Hay
Stewart-Hay Associates
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Re: High strands and min wall 5 years 10 months ago #351

Thanks a lot for your information Peter

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Re: High strands and min wall 5 years 10 months ago #352

Are you bunching the conductor or purchasing it?
Either way you have to be certain that the bunching operation is done with the same constant tension on all strands. When we made bunch stranded wire at the old Pacific Electricord, we always bunched the conductor with hard strands. It was easier to control the tension on hard strands as they are stronger. Then we batch annealed the conductor after stranding and had far fewer high or broken strands.

I don't know if you can get this type from your vendor if you purchase it.
Don Dodge
Calmont Wire & Cable

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Re: High strands and min wall 5 years 10 months ago #353

Actually this core is provide by a external supplier and his process is very variable , sometimes we don't catch any high strands in weeks and sometimes it is very common , all this affects the production,I have to move parameters on my machines , change tooling

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