In-Line Monitoring of Sheath Thickness &
Integrity for LAN Cables

Summary

Specifications to be met by all data cables of category 5, 6 and more are higher in every respect. The extrusion of the sheath, the last manufacturing step, also needs special attention due to following facts:

- thin sheathing
- narrow specs for thickness and eccentricity
- expensive material (flame retardant cables, etc.)
- non-circular or loose substructure
- no shielding (e.g. UTP types)
- no-default sheathing

Normal methods for thickness measurement and fault detection can hardly fulfil such stringent requirements.

This contribution describes methods and systems for reliable in-line measurement and control of sheathing thickness and eccentricity and for detecting local faults such as pinholes, cracks, bubbles and the like.

The worldwide communication market is expanding at an unparalleled rate. It is also a market reminiscent of the good old days of the gold rush. Everything should be done to meet the unfulfilled needs of humankind for better communication. Such a trend sets increasing challenges, from better product quality to zero-defect. This requires of course new test methods in the cable industry.

The Communication Cable Market is In The Dumps!

Zumbach's own R&D have brought new technologies and methods to the field of in-line measurement techniques. Listening with attention to our customers and incorporating their special requirements into the development of products has led us to where we are today:

The following principles are well-known and are used for measuring sheathing thickness:

- Laser-scanning
- Eddy currents (inductive)
- X-rays
- Ultrasound

Each of these methods has its strengths and weaknesses or is restricted to certain types or structures of cables.

Fields of Application/Advantages

Personnel, machinery, products, methods, business considerations, all these factors influence the choice of measurement techniques and their implementation. "In-line" measurements have become an absolute requirement. The quality of a product should be controlled as fast and as soon as possible during the manufacturing process. This significantly diminishes the risk of systematic and random errors while being more cost-effective. Scrap costs money, processed scrap costs even more money. A suitable in-line system that continuously watches many parameters provides a seamless monitoring of control or tolerance limits and a timely warning when these are exceeded.

3.1.1. Method
This method measures the diameter before and after the extruder. Measuring heads 1 and 2 and the processor unit form a closed control loop that allows computing and controlling the average wall thickness.