Background Image
Table of Contents Table of Contents
Previous Page  57 / 64 Next Page
Information
Show Menu
Previous Page 57 / 64 Next Page
Page Background

55

www.read-wca.com

Wire & Cable ASIA – July/August 2016

2.2 Spark Tester

A spark tester is equipment that can be used to detect

pinhole-type defects. The machine creates a spark when

there is a pinhole that exposes the core of the cable –

conductive metal. However, if a pinhole does not expose

the core, the spark is not created. But the pinhole that

is not a through hole is still a defect since over time the

pinhole could expand and expose the core of the cable.

Also, for products without a core (pipe, hose, tubing) or

products without a conducting core (fibre optic cable),

spark testers are not applicable.

2.3 Vision Systems

Prior configurations of surface defect detection systems

were unable to identify and measure convolutions of

the product. These systems were limited to ignoring

the convolutions to identify significant defects such as

pinholes or significant bulges or shape changes. The wrap

inspection system has been improved with additional

image processing software and alternative camera

configurations that identifies the wrapped cable profile

and can measure parameters and detect variations in the

wrapping that are considered defects.

3 Machine Vision Inspection System

3.1 Optical Mechanical Design

The wrap defect inspection system consists of one or

more high resolution cameras and adequate lighting

to capture images of cable moving at speeds more

than 1,200 feet (400 metres) per minute. Using multiple

cameras, 360-degree coverage of the cable surface can

be achieved. The system produces high quality images at

these speeds with a very high frame rate. The frame rate

is synchronised with an encoder and speed algorithm. The

lighting varies depending on the application.

The factors in consideration are the reflectivity of the

material, surface profile, colour, line speed and camera

type.

To ensure consistency in the images, the setup features an

enclosure to prevent ambient lighting, outside particles,

etc from affecting the results. Vibration of the cable is

minimised by cable guides, preventing images from being

out of focus.

An advanced algorithm is used to process the images

for cable wrap inspection. A typical algorithm is capable

of detecting surface and wrapping defects such as

scratches, holes, uneven wrapping, incorrect wrapping

angle, tape peeling and tape tears. The algorithm requires

analysis of the pixels of the image and grouping them for

further interpretation. If a defect is detected, an alarm

will notify the operator and an error report is saved to the

on-going data log. The defect will also show up on the

display for operators to clarify.

3.2 Improving Quality Assurance

Suitable for any type of products

: Since the surface defect

detection system with accurate diameter measurement

uses machine vision, it can be used to inspect the surface

for many types of wrapped products or convoluted

profiles.

It is the most thorough method of detecting wrapping and

surface flaws available and the advanced algorithm can

help classify the type of defects accordingly.

Figure 1

:

Uneven wrapping

Figure 2

:

Surface blemishes

Figure 3

:

Tape peeling

Figure 4

:

Tape wrinkle

Figure 5

:

Armour puckering

Figure 6

:

Discolouration