GSD (General Sewing Data) is a predetermined motion time system (PMTS) made for sewn products. Instead of timing an operator with a stopwatch, the engineer describes the method as a sequence of standard motions, and each motion has a fixed time value.
How it works
- Watch or design the best method for the operation.
- Break it into basic motions - getting parts, putting them in position, sewing, trimming, disposing.
- Select the matching standard codes and add machine sewing time based on stitch length, speed and seam length.
- The software or tables add the times and allowances to give the SAM.
GSD times are measured in TMU (Time Measurement Units):
Formula: 1 TMU = 0.00001 hour = 0.036 seconds = 0.0006 minutes
So an operation of 1,000 TMU takes 0.6 minutes before allowances.
Why factories use GSD
- Consistent SAM: the same method gives the same time in any factory, independent of one operator's speed.
- Method first: because you must describe every motion, waste becomes visible before production starts.
- Faster costing: SAM can be set from the design and sample, before the style reaches the line.
- Common language with buyers: many brands accept GSD-based SAM.
Time study vs GSD
| Time study | GSD | |
|---|---|---|
| Based on | Measuring real operators | Standard motion data |
| Needs rating | Yes | No |
| Good for | Operator capacity, training needs | Setting standard SAM, method improvement |
Most factories use both: GSD to set the standard SAM and method, and time studies to measure each operator's real capacity against it.
Tip: GSD is only as good as the method you describe. Always check the method on the floor with a trained operator before using the SAM for targets.