Mechanical Application Brief

Fabric Testing

The Solution

Richard Chmielowiec chose DADiSP, the graphic display and data processing software from DSP Development Corporation, to provide him with flexible visual display and analysis capabilities for his sewing research station.

Collecting Stitch Data

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 a personal computer and from there to a plotter and printer.

Fabric Properties Analysis

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.

DADiSP for Efficiency Standards

Chmielowiec states that he appreciates DADiSP's ability to store large amounts of data in several formats. "I like DADiSP's 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.