WCA September 2012

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Wire & Cable ASIA – September/October 2007 126 12
Abstract
The use of the Print Verification (PV) system in detecting
print defects greatly improves quality assurance of wire
and cable. Defects on the jacket are continuously detected
by a machine vision system at production line speed.
Images of the defects are processed and saved.
This technology improves the print quality of the cable
produced and by greatly reducing defective products from
reaching the customer.
1 Introduction
Print defects are generally the biggest single source of
defects in power cable and fibre optic cable manufacturing
facilities.
Wrong messages, print smudging and faded prints are
print defects that should not be on good quality products.
The defects are not only cosmetic problems, but the
wrong message can lead to misuse of the cable when it
reaches the end-user. By being able to detect the defects,
corrective actions can be taken at the production level and
defective pieces can be reprinted or discarded.
The PV system uses machine vision technology to analyse,
isolate, and identify print defects. The system runs inline
and saves the all defect image data including length and
defect size in a database.
The camera is generally positioned close to the printer
to simplify print legend identification and print location.
Images of the print legend are created and processed
through high-speed image processing algorithms and
character verification techniques.
Any illegible or incorrect print legends are detected by the
software, alerting the operator to take corrective action.
The images are stored together with length information
providing further analysis or report generation.
The alert provides operators with instant feedback on
current printing conditions resulting in not only corrective
actions, but more importantly allows the operator to
identify and reduce the root causes of the print defect.
This reduces the print defects before they actually happen;
improving print quality, reducing rework cost, wasted
consumables, and defective products.
The PV system can also easily integrate to your lines and
works well for all types of printed cables (twisted pair,
jacketed, bare wires, and convoluted profiles).
The system will be able to analyse print legends done
by any type of printing method such as hot foil, inkjet,
emboss, indent, laser, and gravure printing.
Maintenance on the unit involves a quick wipe when the
unit is dusty. The lifetime of the lights can be over 50,000
hours of usage, and they are the only consumable part in
the whole system.
2 Various Print Detection Technique
Limitation
2.1 Inline Visual Inspection Using Stroboscope
This type of inspection involves using a stroboscope
inline. A stroboscope flashes light at the proper period
to make the print legend appear to be slow moving or
stationary. This gives some time for the operator to verify
the existence or quality of the print. However, one limitation
is that there is not enough time to carefully verify lengthy
print legends until the next print shows up. As well, the
flashing light strobes can be a nuisance to the operator.
2.2 Offline Viewing Through Magnifying Lens
One technique to detect print defects is having the
operators look through a magnifier. Although the operator
can see the print defects and categorise them accordingly,
there are a lot of limitations. The operator can only read the
print up to a certain speed.
Cable Print
Verification system
By Craig Girdwood, Taymer International Inc, and Brian Franklin, Commscope
❍ ❍ Figure 1: Taymer Print View System