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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

Re: High strands and min wall 2 years 8 months ago #354

Hi All,

Just to inform you that the high strands and the minimum wall were improved a lot with some visits to our core supplier in which we saw a lot of "details" on their process. The buncher area was the most important due some tensions on the strands also some ceramics and pulleys out of specification. Well after our visits they improved a lot on all the products. Actually they are working closely to maintain the OD of the core constantly and this helped us a lot on improving the minimum wall (concentricity). We now actually have 90-95% concentricity for PPE (polyphenylene ether) material and for PVC (bunched core) we are between 85% and 95%.

The next step for me is to use a compression guide that will help to maintain the core more centered on the insulation (due the the head pressure). Well this is the theory! Does anybody know about some fixture or something like that to use before the cross head for get a better alignment for the core? Any ideas will be appreciated.

Regards to all on this honorable forum.

Angel
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Re: High strands and min wall 2 years 8 months ago #355

It is always good practice to guide the bare wire into the cross head on center and this can be done with any ceramic or carbide guide mounted either on the entry side of the cross head or on a separate stand (bolted to the floor) behind the cross head. This assumes of course that you are reasonably on center to start with.

The guiding of the wire for center in the plastic however is by the tip (guider, nipple) part of the extrusion tooling and this is already inside the cross head. The tip is the last piece of tooling to touch the bare wire and it is just before the die.

The clearance in your tip is probably fairly large because of the high strands you have been experiencing (The force of gravity usually makes the wire lie on the bottom of the tip and hence some insulation eccentricity is possible.) but we don't recommend that you reduce this clearance without careful experimentation. (See below) We recommend your process engineering people be involved in this.

Presuming that your cross head is not of "fixed center" design, then you can adjust the center with the four centering bolts at 90 degrees separation on the die holder. You can also move the tip a little closer to the die but you really need your process engineering people involved so that you don't damage the tooling or negatively impact plastic properties.

If however you have a "fixed center" design cross head then all you can do is experimentally reduce the clearance in the tip slightly and incrementally until such time that you get an acceptable trade off between the number of wire breaks at the extrusion line and the concentricity you are trying to achieve.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
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Re: High strands and min wall 2 years 8 months ago #356

Hello Forum,

Could somebody recommend some brands of induction core preheaters?

This is to improve some physical properties on specific cable gages. I would appreciate your answers.

Angel
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Re: High strands and min wall 2 years 8 months ago #357

Hello again Angel,

This time we need to know all the gages of wire and metals that you are extruding the plastic on. The bare wire is induction preheated just prior to the extruder crosshead. Thank you.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
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Re: High strands and min wall 2 years 8 months ago #358

Our company is a supplier of Induction Preheaters and as Peter mentions, we need the exact wire sizes and types (bare copper, tinned, braided core, etc...), line speeds for each plus the temperature that you are shooting for. The machines are typically custom made per application and will vary sheave size, amount of power and the frequency utilized. The main attribute change using preheating is in the adhesion of the polymer to the wire.


Erik Macs
VP North American Machinery Sales
Fine International Corporation
148 Oak Street
Natick, MA 01760 USA
508-315-8200 fax: 615-658-1988
This email address is being protected from spambots. You need JavaScript enabled to view it.
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