Integrated Time Study and Line Balancing Project

Why it matters

An integrated project shows that the chain from measurement to an implementable flow is carried in a single file with a single set of assumptions. The chain runs as follows: data and scope log, observed time, normal time from the performance rating, standard time from the allowance, sample size decision, takt time, Yamazumi chart and line balancing, stock-flow, priority of quality and maintenance losses, the split between cost, capacity and cash, and finally the 30-60-90-day verification. Each link takes the output of the previous one as input. If one link works at a different scale or in a different version, the later results look consistent within themselves but do not support each other.

Closing the totals means checking the calculation from the end back to the start. The sum of the station loads in the balancing table must equal the sum of the standard times in the measurement file. When this total is multiplied by the daily units and combined with the idle time, it must reach the number of workers times the available time. The lead time on the stock-flow sheet must be reproducible from the stock quantity and the takt time. These look like calculator work, but the real purpose is to hunt for assumptions: if a total does not close, two tables are not counting the same thing at the same scale. The difference that will not close usually comes not from rounding but from a unit, a version or a time basis.

The most common conflict is a shared assumption written differently in two places. Takt is calculated from 450 min without deducting breaks, while the balance table is prepared with 420 min. The measurement table is in s/unit, the replenishment table in min/batch. The measurement file is at version v2, while the plan was made with the performance ratings of version v3. These errors are invisible when each calculation is viewed alone, because each calculation is correct for its own input. For this reason a shared assumptions sheet goes into the decision file: available time, unit, demand, scrap rate, allowance rate and version number are written in one place and every sheet is linked to it. Changing one assumption means recalculating the whole chain.

The Yamazumi chart and balancing produce the number of workers; quality and maintenance losses show how fragile that number is; stock-flow tells where the queue builds up. All three must be tied to the same constraint: if there is scrap, the number of units to launch rises, takt shortens, and the margin of the constraint station melts away. The number that shows the remaining margin ranks which loss item to touch first. With Yamazo Studio you can mark elements for a video time study, draw the Yamazumi chart, balance the line, produce a standard work sheet and export Excel/PDF reports; but what catches conflicting assumptions is not the tool, it is the closing check in this lesson.

Finally, cost, capacity and cash are kept on separate lines. Freeing one worker opens 420 min/day of capacity; this capacity does not reduce cash expense unless it is assigned to another task. The verification plan keeps this separation: measurement is tested on day 30, losses on day 60 and output on day 90, and the acceptance limit of each check is written in advance. In this way the project becomes a decision file whose presented numbers can be reproduced and, if wrong, corrected.

Formula