A sewing line is only as fast as its slowest operation - the bottleneck. Line balancing means sharing the work so every operator has a similar load and the line produces more with the same people.
Key terms
| Term | Meaning |
|---|---|
| SMV | Standard minutes for one operation |
| Cycle time per operator | SMV ÷ number of operators on that operation |
| Pitch time | Total garment SMV ÷ total operators (the ideal, perfectly balanced time) |
| Bottleneck | The operation with the highest cycle time per operator |
| Balance efficiency | Pitch time ÷ bottleneck time × 100 |
Example
A small line has 11 operators and a garment SMV of 6.05 minutes.
- Pitch time = 6.05 ÷ 11 = 0.55 min
- The collar attach operation has SMV 1.10 with 1 operator → cycle time 1.10 min (the bottleneck)
- The line can only make 60 ÷ 1.10 = 54 pieces per hour
- Balance efficiency = 0.55 ÷ 1.10 = 50% - half of the paid time is waiting
Add a second operator to collar attach and its cycle drops to 0.55 min. The next slowest operation becomes the new bottleneck, and output rises.
How to balance a line
- List every operation with its SMV (from the operation bulletin).
- Divide each SMV by the pitch time to get the theoretical operators needed.
- Round sensibly and group small operations for one operator, keeping them on the same machine type and close together.
- Place your highest-capacity operators on the heaviest operations.
- Check the result: no operation should be more than 10-15% above pitch time.
Tip: Balance with real operator capacity from time studies, not just SMV. Two operators with the same job title can differ by 30% in speed.
Keep it balanced
Absence, machine breakdowns and new operators change the balance every day. Review the line each morning, move multi-skilled operators to the bottleneck, and watch WIP - a growing pile before an operation is the clearest sign of a bottleneck.
Try your own line in the free line balancing calculator.