Sewing machine shops in chennai - VS Enterprises
Processing textile materials is generally very
difficult due to the flexible nature of the material. In industries
using sewing as assembly process, most processes rely on human
labor, being difficult or even impossible to automate. The relations
between machine configuration and adjustment, material
properties, and the resulting product quality are also complex.
This paper describes current work using an instrumented
lockstitch sewing machine to study the dynamics and variations of
one of the important process parameters during high-speed sewing
of shirts: thread tensions. The objective is study the principles that
may allow for an automatic setting of the machines, quality control
and for real-time process control. It has been found that
differences in material properties result in measurable features of
the thread tension signals acquired.
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.
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.
Sewing machine shops in chennai 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].
-Stitch formation/Thread tensions. The interlacing of the
threads itself, which constitutes the actual stitch formation,
cannot be dissociated from the processes of material feeding and
needle penetration. However, there are two variables directly
linked to the thread that most intimately represent it: Thread
tensions and thread consumption. The relationships between
fabrics, machine set-up and stitch formation in lockstitch
machines have already been studied in [9-15]. Methods for
defect detection have been developed for overlock machines and
presented in [3]. However, an automatic system for setting
thread tensions online is still missing. Wang and Ma [15]
describe thread tension control in embroidery machines, but the
work only tackles the issues associated to the control of the
actuator. Setting of the correct references for the controllers to
produce a high-quality product in varying conditions is the key
issue, and this has to be further tackled.
This paper describes current work on the behavior of thread
tensions in an industrial lockstitch sewing machine using a new
measurement set-up. https://vssewingmachine.in/ Methods previously investigated for
monitoring of thread tensions and establishing the correct
variable references are being ported and/or re-evaluated. The
first step is the study of the relations between material properties
and thread tensions. Some aspects are still not clear in this
regard. In [13], for instance, the authors state that the thickness
of fabric plies does not affect the needle thread tension.
An industrial PFAFF 1183 lockstitch (stitch 301 according
to ISO 4915) machine (Fig.1) has been instrumented with a
thread tension sensor (Fig.2) connected to a signal conditioning
circuit which in turn plugs to a National Instruments PCI-MIO16E-1 data acquisition board (although often called thread
tension, the parameter measured is actually a thread pulling
force). The machine’s “synchronizer” (a rotary optical encoder)
provides 512 pulses per rotation of the machine, which is used
as sample clock for signal acquisition. It is thus possible to
determine the exact angle at which each signal sample is
acquired, allowing relating the signal directly with the events
during the stitch cycle. Signals are thus represented on a
continuous angle rather than a time scale, in which the rotation
N of the machine corresponds to the angles between 360º·(N-1)
and 360º·N.
The sensor (custom-designed by Petr Skop) is a cantilever beam
with semiconductor strain gauges at the base, configured as a
complete Wheatstone bridge. A glass sphere with a rounded slot
allows a low-friction interface with the sewing thread. A thread
guide with two ceramic O-rings has been designed to guide the
thread around the thread sensor. The thread pulling force
produces deformation on the cantilever sensor that is picked up
by the strain gauges.
Thread tension is imposed to sewing threads by a device
called a tensioner (partially visible in Fig.2). This device consists
of two disks between which the thread passes. A spring holds
the two disks together. The pre-tension of this spring can be
adjusted and is called in this context static thread tension.
A software application has been developed in Labview
allowing the acquisition and processing of the resulting signals.
The signal processing functions of this software have been
reported elsewhere [3]. The most important one is splitting the
thread tension signals into stitch cycles (each cycle
corresponding to one rotation of the machine’s main shaft) and
in turn dividing each stitch cycle into phases, which are
associated to specific events of stitch formation. For each one of
these phases, that will be described later, features such as peak
values, power, energy or average of the signal is computed.
In the current experimental work, thread force waveforms
throughout the stitch cycle are being analysed when varying
parameters such as static thread tension adjustment, number of
fabric layers, mass per unit area and thickness of fabric, needle
size and sewing speed. Both the effect of the machine settings
and process variables on the thread tensions, as well as the effect
of the material properties are investigated. In this paper, the
effect of static thread tension and the influence of the fabric on
the dynamic tension signals are analysed.
The first step was to observe the resulting thread tension
signals and interpret their relation to the stitch formation
process. Some trials with the adjustment of the needle thread
pre-tensions were made.
Afterwards, a more comprehensive experiment was set up to
investigate on the influence of the material being sewn.
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