Seam and pattern inspection

Need

The seam is sewn with thread in the fabric's own colour and gives low contrast on the raised texture; a shift of a few millimetres in a striped pattern is not noticed by eye but is obvious on the finished garment. Fabric stretches, and the panel never stops at exactly the same place on the belt.

Solution approach

A top-view camera images the seam area under low-angle bar lights from both sides; the low angle brings out the seam relief with shadow. The seam line is traced as an edge and stitch pitch is measured; the stripes are located on both sides of the seam and the offset is calculated in millimetres. The measurement is referenced to the panel's own seam, so the belt position does not affect the result.

Process steps

1. 01

   Infeed

   The sewn panel moves under the camera on the belt and stops; the photo-sensor reports its presence.

2. 02

   Acquire

   The bar lights strobe and the top-view camera images the seam area.

3. 03

   Seam

   The seam line is traced; stitch pitch and straightness are measured.

4. 04

   Pattern

   The positions of the pattern stripes on both sides of the seam are compared.

5. 05

   Decide

   Pattern offset and stitch pitch are compared with their tolerances; a panel out of tolerance is marked.