Line balancing is the process of assigning sewing operations to operators so that each workstation takes roughly the same time, and work flows without piling up. You start with the SMV (standard minute value) of each operation, calculate the pitch time (total SMV ÷ number of operators), and then allocate operators so no operation is slower than the pitch time. The slowest operation, the bottleneck, decides the output of the whole line.
Thirty operators, one placket
This is a composite scenario drawn from situations we see often in Indian factories.
Anil manages a polo shirt line in a Noida export unit. Thirty operators. An eight-hour shift. A daily target of 600 pieces that the line has not hit once in three weeks. The line keeps closing at around 450.
Anil does what most good supervisors do. He walks the line, pushes the slow operators, shifts a helper here and there. Output goes up for an hour, then drops back.
On day 22, a young IE trainee sits next to the placket-attaching machine with a stopwatch. She finds the operator’s actual cycle time is about 1.1 minutes per piece. That’s roughly 54 pieces an hour, or around 436 in a shift. Every other operation on the line is faster.
In other words, the line was never going to cross about 440 pieces a day, no matter how hard anyone pushed the other 29 people. The ceiling was one machine.
What line balancing actually means
A sewing line is a chain. Each operator does one or a few operations, then passes the bundle on. If one link is slower, everything behind it waits and everything in front of it piles up as WIP. Line balancing is the discipline of making every link take roughly the same time.
It rests on three numbers: SMV, pitch time and target.
Step 1: Calculate SMV for each operation
SMV (standard minute value), also called SAM, is the time a trained operator should take to complete an operation at a normal pace, including allowances.
SMV = Observed time × Performance rating + Allowances
Worked example:
- Observed average time for “attach collar”: 0.40 min
- Performance rating of the operator observed: 90%
- Basic time: 0.40 × 0.90 = 0.36 min
- Allowances (personal needs, fatigue, machine delay): 15%
- SMV: 0.36 × 1.15 = 0.414 min
Many factories also use predetermined time systems (such as GSD) instead of stopwatch studies. Either way, the goal is a reliable, agreed time per operation.
Step 2: Build the operation bulletin
An operation bulletin (OB) lists every operation in sequence for one style, with its SMV, machine type, and the number of operators needed. It is the blueprint for setting up a line.
| Operation | Machine | SMV (min) | Theoretical operators | Allocated |
|---|---|---|---|---|
| Shoulder join | Overlock 4T | 0.38 | 0.91 | 1 |
| Placket attach | Single needle lockstitch | 0.85 | 2.04 | 2 |
| Collar attach | Single needle lockstitch | 0.41 | 0.98 | 1 |
| Sleeve attach | Overlock 4T | 0.72 | 1.73 | 2 |
| Side seam | Overlock 4T | 0.80 | 1.92 | 2 |
| … other operations | … | … | … | … |
| Total style SMV | 12.5 | 30 | 30 |
The “theoretical operators” column comes from Step 3.
Step 3: Calculate pitch time and allocate operators
Pitch time = Total style SMV ÷ Number of operators
For our polo: 12.5 ÷ 30 = 0.417 minutes
Operators needed for an operation = Operation SMV ÷ Pitch time
Placket attach: 0.85 ÷ 0.417 = 2.04, so it needs two operators. Anil’s line had one. That was the entire problem.
Step 4: Set a realistic target
Target at 100% efficiency = (Operators × Working minutes) ÷ Style SMV
(30 × 480) ÷ 12.5 = 1,152 pieces per day
No line runs at 100%. If your line typically runs at 55% on a mature style, the realistic target is about 634 pieces. A target of 600 was achievable, but only with a balanced line.
Line efficiency = (Output × Style SMV) ÷ (Operators × Working minutes) × 100
At 450 pieces: (450 × 12.5) ÷ (30 × 480) × 100 = 39%
How to find the bottleneck quickly
- Look for WIP piles. Bundles stack up just before the bottleneck and the next operator sits idle.
- Check hourly output by operation, not just end-of-line. The bottleneck has the lowest hourly count.
- Compare capacity per operation. Capacity per hour = 60 ÷ actual cycle time × number of operators on it. The lowest figure is your ceiling.
- Watch for “hidden” bottlenecks. A fast operator who also does a second operation, or a machine that stops for thread breaks, can quietly become the constraint.
Five ways to fix an unbalanced line
- Add an operator to the bottleneck (as with the placket above).
- Split the operation. Move part of a long operation to a station that has spare time.
- Use a multi-skilled operator who can support the bottleneck when WIP builds up.
- Improve the method. A folder, guide or attachment can cut seconds from a repetitive operation.
- Change the machine. Sometimes an automatic or specialised machine pays for itself in weeks.
Why line balancing on paper breaks down
The OB is drawn up on day one. By day three, two operators are absent, one machine is down and a new operator has joined. The paper OB no longer matches the real line, and nobody updates it.
That’s where live shop-floor data matters. When each bundle is scanned at each operation, you see hourly output by operation and by operator, as it happens. The bottleneck shows up in the data, not just on a trainee’s stopwatch.
Where TPCS fits
TPCS MES includes:
- Time and motion study (OB): build and store operation bulletins with SMV for every style, so you aren’t rebuilding them from scratch.
- Line balancing: allocate operators based on SMV and pitch time.
- Bundle and component tracking (QR or RFID): every bundle scan updates output by operation.
- Visual display boards: live line efficiency and hourly output on a screen the whole line can see.
- Operator efficiency reports: so you know who can support a bottleneck tomorrow.
How Anil’s story ended
Anil moved a multi-skilled operator from the side seam station, which had spare time, to placket attaching. The line hit 560 pieces on day one and 610 by the end of the week. The trainee’s stopwatch study became the line’s first proper operation bulletin, and the factory now builds one for every new style before it goes to the floor.
Frequently asked questions
What is line balancing in the garment industry?
It is the process of distributing sewing operations among operators so that each workstation takes about the same time, which keeps work flowing and maximises output.
How do you calculate SMV in garments?
SMV = Observed time × Performance rating + Allowances. For example, 0.40 min observed × 90% rating = 0.36 min, plus 15% allowance = 0.414 min.
What is an operation bulletin?
A document listing every sewing operation for a style in sequence, with machine type, SMV and required operators. It is used to set up and balance the line.
What is pitch time?
Pitch time is the total style SMV divided by the number of operators. It is the ideal time each workstation should take for a balanced line.
What is a good line efficiency in Indian garment factories?
It varies by product and style maturity. Many Indian units run in the 40–60% range; well-managed lines on repeat styles go higher. Track your own trend rather than chasing a generic benchmark.
Want to see your bottleneck in real time?
Book a TPCS demo and we’ll show you how operation bulletins, line balancing and bundle scanning work together on a live line dashboard.