Research of fabric and sewing thread

As garment manufacturers compete to increase rates of production, an increasingly important objective of research in the industry is to find fabric and thread combinations that can be sewed at high speeds without producing defects.

Sewing is one of those ancient human activities that is difficult to automate because there are too many variables with wide parameters.

Putting together a garment, for instance, requires choices of fabric and thread, variation in stitch size and thread tension, and the ability to compensate for aberrations in materials, among other factors.

Richard Chmielowiec, a doctoral student at the Hong Kong Polytechnic in London, is conducting research into setting up a system for testing a factor he calls sewability- the capacity of a fabric and thread combination to be sewn without producing defects such as seam buckling.

He investigates dynamic conditions during high-speed sewing to determine which variables involved in sewing a good seam can be tested reliably.

Chmielowiec's RSTM/SPMS instrumentation is called an ETS (experimental testing sewability) station, where RSTM stands for Richard's (Chmielowiec) sewability testing method, and SPMS stands for seam pucker measuring system.

The instrumentation consists of a state-of-the-art Pfaff lock-stitch sewing machine with several sensors attached and uses a textile evaluation method called image processing analysis.

The station's data analysis software must be flexible enough to perform many kinds of analyses, and it must be menu-driven, so researchers can learn to use it in minimal time.

Finally, it must be highly compatible with other software and hardware components, to accommodate changes in instrumentation and analysis methods over time. Richard Chmielowiec chose Dadisp, graphic display and data processing software, to provide him with flexible visual display and analysis capabilities for his sewing research station.

During an RSTM test, a straight seam is sewn on the Pfaff sewing machine, and signals are acquired by the six attached transducers.

One A/D sensor is currently free for future design changes; the other three pick up needle penetration force (NPF), presser foot pressure force (PFD; the presser foot is the metal piece that holds down fabric for the needle), and sewing thread tension (STT).

Two more transducers pick up digital signals: presser foot displacement (PFD) and real-time clock signal/system calibration.

Data are generated at a rate of up to 480 points per shaft rotation, a cycle in which the needle moves down and up again to make one complete stitch.

The four A/D signals - NPF, PFF, STT, and PFD - are displayed on a plot.

These signals are amplified, then all six signals are transformed via data translation boards and acquired through specially designed software programs.

Data go to an IBM-compatible 386-based personal computer and from there to a plotter and printer.

Once an adequate amount of data is stored, Dadisp is used for further analysis.

Using the incoming data, signals are separated from noise and peaks are found in the time and frequency domains.

The results are compared with the properties of fabrics and threads being tested and are finally correlated with the incidence of seam buckling at the tested parameters.

Chmielowiec states that he appreciates Dadisp's ability to store large amounts of data in several formats.

He also likes its flexibility in carrying out many kinds of analyses as new ideas arise.

His instrumentation has proved successful, and has now been assembled at the Hong Kong Polytechnic for permanent use.

Research such as his will ultimately result in efficiency standards and materials recommendations across the industry.

Dadisp is supplied and supported in the UK and Ireland by Adept Scientific.