There are several papers that have been given over the years at the WAI Tech Conferences related to Cat 6 cables. You can search the abstracts in the main page of Wirenet.Org (Technical - Abstract Search). I don't specifically recall any papers dealing with the design calculation related to lay length relationship, however.
Lay length is only one of the parameters critical to suitable Cat 6 production. Several key items to also consider -
*inline drawing during the extrusion process
*concentricity and adhesion of the insulation material
*backtwisting of the individual conductors during the twinning process
*sheave diameter during the various process steps
*Accuracy of the lay of the twinned pairs
*use of a central X member in the 4 pair construction
*tension control, tension control, tension control
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How is your R & D technical library coming along? As we advised you in that particular thread and as Eric Macs has already advised you this morning:
(a) Click on the WIRENET.ORG logo above, review and search the Wire Journal International Archives plus use the Abstract Search and purchase the technical papers you want. You should always start by doing this search and in this particular case, use key words are "category 5", "LAN cable" and "data cable". One good paper is "Copper LAN cables: have they reached their speed limit? by Jose M. Castro and published in the Wire Journal International in August 2004.
(b) Research what other companies are offering. On the Internet, go to Belden CDT Inc. www.belden.com/ and see what they say in their cable college. Get their product specifications and learn the standards they reference. Purchase those standards. Likewise go to Berk-Tek www.berktek.com/ and get their product specifications.
(c) Go out and buy reels of category 6 cable from various manufacturers and have your product engineering department carefully disect and fully analyze their designs. That will tell you the pitches and the diameter over the dielectric (DOD) The standard insulating/ jacketing materials are PVC although FEP (solid and foam) is used for the plenum variant. (Hint - Remember that if they strand with no backtwist, there will be a small effect on the pair pitches.)
(d) Talk with companies like Sikora and Beta LaserMike to see what they recommend for instrumentation for your primary insulation line and make sure that this line is really well maintained and under tight control electronically. It should also have tandem drawing/annealing for stability as you will be manufacturing the PVC singles at speeds in excess of 4,000 FPM.
(e) On the assumption that you already make communications cables and are aware of what the terms near end crosstalk (NEXT), the easier to achieve far end crosstalk (FEXT) and structural return loss (SRL) mean and that you may have the appropriate instrumentation in your test department, talk with your product engineers and test department people to determine the test equipment if any you have to purchase. If don't have qualified product engineering and test people, hire them and buy the necessary test equipment.
(f) Talk with companies like Northampton, SETIC and others to see what they recommend for pair-stranders or just twinners. (Hint- Think planetary or with backtwist.) (Hint - As Eric Macs aleady stated, tension control throughout manufacture, including sheathing and spooling is really critical.)
(g) Make the appropriate decisions and start your project.