Thursday, November 5, 2009

How Low Voltage Cable is Made - Cat5e, Cat6, Cat3 and OSP

In this article, I'll explain step by step how low voltage Premise and Outside Plant (OSP) cable is made. This includes Cat3 telephone cable, Cat5e, Cat6, Armored, Gel-filled and more. Enjoy

Copper Rod Breakdown
The first step in low voltage cable production is copper rod breakdown. Copper is sent to the factory in 5,000lb coils. These copper coils are continuously drawn through diamond dies that drastically reduce the diameter of the copper to 10 or 12 gauge. Lubrication is used during this process to reduce the amount of friction and heat on the copper cable. Once completed, the copper is stacked in vertical coils, called Stem Packs. These stem packs are then transferred to another drawling operation that further reduces the gauge of the copper. During this stage, the copper is also charged with an electrical current. This anneals the copper, which is a softening process. Once annealed and cooled off, the copper runs through a laser measurement system, to verify it is within manufacturing specifications.

Copper Insulation Process
The copper insulation process is continually monitored and controlled up to +/- .0001". Once the copper is insulated, it runs through a water cooling trough, allowing the wire jacket to properly harden.

Copper Twisting
Twisting helps reduce crosstalk between the individual pairs of wire. Some Cat6 premise cables include a center spline, or wire separator, to further reduce crosstalk and increase performance. Copper twisting is accomplished by running each individual wire through multiple faceplates. This helps control pair position. Once twisted, we have what's called a Cable Unit.

The cable unit then goes through the jacketing process. This step varies, depending on what type of cable your manufacturing. OSP cable typically uses a black polyethylene or UV rated Polyvinyl chloride (PVC). For Cat3, Cat5e and Cat6 Premise cable, varying grades of PVC are used, depending on flame safety rating requirements. This steps starts off with molten plastic being extruded at high pressure and formed around the moving cable core. Shielding, ripcords, armoring and water blocking compound may also be applied at this step. Cables that require dual shielding or double armor will need to repeat this process. Once completed, the cable passed through a long cooling bath, then through a laser micrometer to verify the final diameter.

Printing is done just before the cable is put in it's final packaging. For OSP cable, a hot foil printing process is used, that leaves an indented print in the cable jacket. For Premise cable, a high speed ink jet printer is used. Some cable manufacturers print footage marking from 1000-0ft, making it very easy to determine how much cable you have left in the box, or measuring out cable runs. Other manufacturers use a 6 digit footage mark, making the process a little harder.

The completed cable is then wound onto a reel or coil. the coiling process requires very precise tension controls to insure the cable won't tangle when being pulled out of the box.

Final Testing
Once the cable is printed and coiled, it goes through one last set of tests. The manufacturer will test it against a large set of mechanical and electrical performance specifications. Once tested, the cable is ready for shipment.

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