Calculating Takt time
Calculating Takt time
Time Practical Considerations :
| Takt Time = | Available Work Time |
| Customer Demand |
But perhaps this is too simple. Takt time is the available weekly work time, taking into account the shifts worked and making allowances for planned stoppages (for planned maintenance, team briefings, breaks) divided by the anticipated average weekly sales rate (including spare parts) plus any extras such as test parts and (we hope not) anticipated scrap.
Some companies allow for changeover times in calculating the available weekly work time. This is not really good practice because the takt drumbeat must be maintained throughout the plant, including changeovers. However provided there are good standards for changeover and that batch sizes are calculated keeping in mind the customer's rate of demand, it may be tolerable. Also, some companies make allowances for breakdowns and OEE in available time. This is not so reasonable because this may build in bad practice.
The takt time formula is often best used in relation to a week. A day will often be too short. A month will often be too long, although at Toyota a takt time can remain in force for several months.
Example
A company manufactures brackets. The average weekly sales quantity is 500 brackets. The factory operates on a single 7.5 hour shift, five days a week. There are two 15 minute breaks each day. Planned maintenance takes place each Friday for 2 hours. The yield percentage is 99%. Calculate the takt time.
| Available Work Time | = | Total hours - breaks - planned maintenance | |
| = | (7.5 x 5) - (2 x 0.25 x 5) - (2) | ||
| = | 33 hours | ||
| Customer Demand | = | 500 per week | |
| But yield | = | 99% | |
| Therefore, quantity required each week | = | 500 = 505 | |
| 0.99 | |||
| Takt Time | = | Available Work Time = | 33 = 0.0653 hours = 3 mins 55 secs |
| Customer Demand | 505 | ||
Therefore, one bracket needs to be produced every 3 minutes and 55 seconds.
