The processing of textile
products by sewing them together is a very complicated process. This may not be
apparent at first glance, but a closer look at the process reveals that, due to
the flexible, often extensible nature of the materials, their handling is a
procedure that in almost all cases requires human hand. Another important
aspect is setting the machines for the great variety of materials used
currently. This can only be accomplished by experienced sewing technicians.
Machine configuration and adjustment is an empirical, time-consuming process
that is more and more significant considering that textile industry has been
constantly moving away from massproduction to small orders with varying materials
and styles. juki usha singer merritt sewing machine price list showroom in chennai
Machines should be able to set
themselves up when the data regarding material properties and desired process
parameters is known. During the process, it would be ideal if they could adapt
themselves and detect defects or malfunction automatically. This would reduce
set-up times, increase flexibility of the machines and increase product quality
and process reliability, avoiding defects and rejected products. Research in
this direction has been carried out by several investigators, such as Clapp
[1], who studied the interface between the machine and the material feeding
system, Stylios [2] who proposed the principles of intelligent sewing machines,
amongst others. Within our team, previous work has been carried out on thread
tensions, material feeding and needle penetration forces in overlock machines
[3-5]. Other studies targeted needle and bobbin thread tension measurement on
lockstitch machines [8-10].
The sewing process is a cyclic
process in which several occurrences take place. The objective is to interlace
thread(s) with each other and through a fabric, for the purpose of joining,
finishing, protecting or decorating. Three main “sub”-processes can be
identified that ideally should be monitored and/or controlled automatically:
-Material feeding. Seams are produced on the fabric with a certain pattern,
which is, in the simplest case, a straight line, but may also be a complicated
form such as the ones used in embroidery operations. To form these patterns,
the material has to be transported-“fed” by a distance that is called the
stitch length. Given that industrial machines operate at very high speeds (some
of them attaining 10 000 stitches per minute), the dynamics involved is complex
and there are very often problems with material deformation and irregular
stitch length. Some of these aspects have been addressed in [1-3, 5];
-Needle penetration. Considering
again the high sewing speeds that occur, problems with needle penetration can
arise due to the mechanical and thermal interaction between needle and fabric.
Fabric yarns may be torn by the forces acting during needle penetration or they
may fuse due to the high needle penetration produced by friction. Systems to
monitor needle penetration forces during the process to detect defects and
offline systems to support the choice of needles and fine-tune fabric
structures and finishing to avoid these problems, would be of high value to the
industry. This kind of approach has been studies by several authors, such as in
[4-8].
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