- About me
- A university trained Professional Mechanical Engineer, registered in the Province of Ontario, Canada.
A wire and cable manufacturing engineering specialist with over 35 years hands on experience.
- Hello again,
This is a pretty complicated subject.
PVC screws are designed for high output without burning the PVC. They have deeper channels than PE screws to provide sufficient mixing without high shear.
XLPE extruder screws are designed for low shear and a stable melt pool but stay away from Maddock, Egan, Pineapple and Pin type mixing screws.
I suggest you first read about barrier screws at:
and then get a quotation for the latest cable XLPE barrier screw design from Maillefer at:
Provide them with the complete information on your extruder and PVC screw. Then ask them to give you a sketch of their quoted XLPE barrier screw.
- Hello Adel,
Heat and pressure along with the residence time are the issues causing the XLPE mixture to crosslink.
Although a PVC screw has a deeper pressure section and a modified mixing section to help prevent the PVC from burning, it is really not the ideal screw for mixing and pumping the mixed and now liquefied XLPE compound.
Likewise your extruder has a 25 to 1 length to diameter ratio and a 4.72 diameter screw. I suspect that you have been insulating line wire (Secondary distribution cable.) with this machine. You probably also use water on the screw to reduce the chance of burning the PVC.
As long as you use accurate control of the screw temperature, keep the residence time low, keep to the recommended temperature for the XLPE compound and don't shear the XLPE too much, you will have a reasonable chance of being able to properly extrude the XLPE compound. If this does not work, you will have to invest in a proper XLPE screw with a barrier section before metering.
All will depend on the product you will be manufacturing.
An experiment is in order along with a careful examination of the screw, crosshead, tooling and product after the experiment is over.
- Peter J Stewart-Hay replied to the topic 'Extruding dual color or bi color XLPE Cable' in the forum.Hello again Sasith,
"Aerial bundled cables (also aerial bundled conductors or simply ABC) are overhead distribution power lines using several insulated phase conductors bundled tightly together, usually with a bare neutral conductor." There is only a single insulation application (Black to prevent UV light damage.) and the voltage rating is quite low.
I presume you are to have a colored stripe on each insulated cable or a half black and half colored insulation.
- The first issue is to prevent UV damage to the insulation and generally that negates the use of colored insulation.
- The second issue is to add gravimetric silane and color concentrate mixing to the second extruder.
- The third issue is the size of the extruders as the longer residence time inside the extruders may promote the formation of precure inside the extruders. If it is a colored stripe, you likely would have to purchase a small vertical extruder and a dual crosshead.
- The fifth issue is the relocation and alignment of the two existing extruders so they oppose each other.with a new dual crosshead in between.
We see very little advantage in going through this hassle for such a low profit margin product and therefore recommend against this development.
I think you should talk with your customer and see if there are any other ways he/she can accomplish their goal such as one rib and two ribs on the surface of the black insulation.
- Peter J Stewart-Hay replied to the topic 'graduation about prestressed wire straightness' in the forum.Hello Bram,
If you click on the "WAI Store" heading at the left and go to the second page, you will see two books for sale. These are:
- Ferrous Wire Handbook
- Ferrous Wiredrawing Machinery
Click on each book to see the details inside.
The books aren't cheap but they will provide you with the basic information.
If you are not already a member, I suggest you join the Wire Association International before you purchase the books to reduce the selling price.
- Hello again Mohammad and thank you for the resolution of your rough insulation issue.
It never dawned on me that you would be having such a basic or fundamental problem as precure in the extruder barrel as it was my belief that you had much experience in the manufacture of a saline-grafted, moisture cross-linkable polyethylene system.
It just goes to show just how dangerous an assumption can be.