In recent years, carpet manufacturers in Europe
have had their ups and downs. Their market has not only come under
attack from competitors in the Far East and the United States, but
from fashion trends such as the low cost 'plastic' imitation wood
floor covering as well. Many homes and offices, as well as public
buildings, are furnished with wall-to-wall carpeting which combines
exceptional comfort and hard wearing with excellent sound and heat
insulation. To maintain its market share and reduce costs the companies
were forced to amalgamate into a smaller number of larger firms.
For the European carpet industry to survive such competition it
needed to both enhance its product quality and cut production costs.
A CRAFT project set up in 1994 aimed to reduce both the amount of
defects (thereby improving quality) and the costs of manufacturing.
After two years, the team involved in the 'Fault detection by video
inspection during carpet manufacturing' project had successfully
built a prototype on-line quality control system. The new video-based
system stops the tufting machine as soon as a fault is detected,
eliminating the need for further post-production inspection. It
also helps to optimise machine adjustments, ensuring reproducible
Spinning a yarn
All carpet is produced from the conversion
of a raw fibre. With a few exceptions, this fibre is spun into yarn
which is then made into carpet by one of three methods - weaving,
tufting or bonding. The tufting process, which is a highly automated
and very fast stitching process, is the production method chosen
for well over 80% of wall-to-wall carpet manufacturing. Each tufting
machine inserts between 600 and 2100 stitches per minute into a
backing sheet. A needle sends the yarn stitch by stitch through
the carpet-backing fabric. By briefly stopping the yarn, a loop
builds up. These loop ends will become the carpet surface, known
as the carpet pile or face. In a second step, using other machines,
the roll of carpet has to go through the finishing stages of colouring,
then drying and, if required, printing with a pattern. An additional
backing fabric is then laminated to the carpet to reinforce it before
the manufacturing process is complete.
Any fault occurring in the first stage has to go through the whole
process until the quality is visually inspected and the carpet roll
assessed as either first or second quality. Since the tufting machines
run at very high speeds, producing 25 square metres of carpet per
minute, any fault produces a long length of defective carpet before
it can be corrected. These defects represent 4% or more of production
output, averaging an estimated 50,000 euro annually for every single
An innovative idea
The success story began in Aachen (Germany)
when a good, innovative idea was transformed into an SME (FEG Textiltechnik)
a university spin-off from the local textile academic institution.
Aachen is one of the leading centres in Germany - and in the whole
of Europe - for carpet manufacturing. The directing managers of
FEG gathered six more companies from the tufted carpet industry
and one spinning mill. The partners needed expert scientific help,
and secured the collaboration of two research institutes, the Textile
Technical University and the German Carpet Research Institute, both
based in Aachen. They provided the video image analyser, cable system
and software expertise to process the data. Finally, there were
ten partners in a co-operative and team effort working on the project.
Their aim was to build a machine that would provide a 100% quality
control on-line. Currently, one operator runs just one tufting machine.
As well as controlling the machine, the operator spends two-thirds
of his time looking for tufting faults appearing in the fabric -
the stitched carpet - to detect any production problems.
The first stage of the project was to define carpet quality and
to achieve a consensus of what it was and what measurements were
needed to ensure that consistent, high-quality carpets were being
produced. Only then could a video monitoring system be devised.
The data from the camera is processed and analysed by a computer
programme. The novel and modular system uses a video camera to control
the carpet quality over the entire roll width. The camera follows
directly behind the needle. If a problem occurs - such as a cut
or missing thread of yarn, fabric holes, broken fibres, or other
tufting or stitching errors - the machine is automatically stopped.
The fault can then be rectified before defects are produced. And
this fully automated system only needs one operator to run two machines.
Up and running
A prototype tuft control system is now
up and running and the partners report that labour costs have been
reduced and productivity is up. Technical expertise was the key
to obtaining a satisfactory and efficient exchange of know-how and
information among the tuft producers (who are normally in competition),
the video system producer and the software programming developers.
The video camera system uses a combination of advanced image sensor
technology (in a line rather than a matrix array for higher resolution)
and memory storage, which allows images to be captured in a digital
format that is instantly available for processing and evaluation.
The prototype was not ready for evaluation before the official date
for completion of the project, but the partners carried on their
efforts to complete the work and assess the prototype in production.
The on-line quality control is now in full-time operation in the
partners' factories. They have shown that the new tuft control system
pays for itself in under a year through cost savings accruing from
the elimination of defects and reduction of manufacturing costs.
Today, five machines have been sold and are in operation. The SME
has doubled its workforce to build on this success - especially
in a well-established and conservative industry such as the carpet
sector. It will concentrate now on marketing the system to the many
hundred potential customers throughout Europe and beyond. Already
a new market for the quality control system is undergoing trials.
It can also be used to inspect surface defects in technical textiles,
such as those used to stiffen high-speed tyres, as well as other
materials, like brass wires used in the electronic industry.