WCA September 2015

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96 Wire & Cable ASIA – September/October 2015
Ultra-fast, high
resolution, surface quality
measurement (SQM),
for wires, optical fibres
and cables
By Jean-François Fardeau, Gérald Novel and David Miara, Cersa-MCI, R&D division, Cabries, France
Abstract
This project meets a long-time wire, cable and fibre
industry requirement for efficient in-line surface quality
measurement and defect detection. It was recently allowed
by the very latest technology progresses in optoelectronics.
The system works like a ring linear camera around the
wires. The fine wire version works from 10μm (0.4 mils) to
2mm (80mils) in two models, fine and ultra-fine. With 64
dots per circumference, about 300,000 circumferences
per second (c/s), and a dot size proportional to the wire
diameter, it brings surface detection performance far above
all present existing technologies at a competitive cost.
It includes all necessary real-time electronic computing:
defect characterisation and selection, and alarms.
It connects to external computers for data logging,
parameter setting, and image display of the surface on
PC screen, statistic computing, production quality reports
and maintenance. (International patent July 2004). Other
models, for larger diameters and higher resolutions but
lower speed, will follow by next year.
Introduction
In applications where surface quality (roughness, flaw,
lump, neck) is critical, like special fine stainless steel wires,
gold wires, wire plating, coatings or colourings of optical
fibres, enamelling of copper wires and broadband cables,
there was no instrument for high resolution and high-speed
whole-surface analysis.
The existing surface quality instruments are based on
standard camera image analysis. The limits for fine wire
are the resolution on the wire, the image frequency, and the
lighting system for surface analysis.
With the non-contact full circumference imaging, this
covers all the surface of the wire at high resolution and high
speed.
It becomes possible to evaluate the surface and shape
of the defect. At 300,000 circumferences per second and
64 dots per circumference, at line speed of 30m/s (1,800m/
min) the axial resolution (pitch) would be 0.1mm (4 mils).
Including the wire feed pulses for wire length and speed
measuring, the two dimensions are known: length and
circumference. That gives a two-axis image of the wire
for defect characterisation. Connected to a PC, this can
display local images of the wire surface, especially when
there is a defect, for analysis and knowledge.
Using only static components, lifetime is not a problem.
Maintenance of optical systems in harsh environments
requires specific care.
For low maintenance action, it uses clean air pressure to
avoid dust, vapour or particles deposition on the inner
glass tube interface.
Principle
The idea came from the gleam of a spotlight on a cylinder.
In this image, re/D is about two per cent. Then re/π*D < 1%
of the circumference. The size of the gleam depends of the
size of the spot source and of the angular aperture of the
observer (optic of the sensor).
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