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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.
1. Introduction
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.
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The Communication Cable
Market is In The Dumps!
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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:
2. Principles of Methods
for Sheathing Thickness Measurement
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.
3. Comparative Analysis of
Methods
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. Laser Technology
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.
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