Takt time
Takt time, derived from the German word Taktzeit which translates to cycle time, sets the pace for industrial manufacturing lines. For example, in automobile manufacturing, cars are assembled on a line, and are moved on to the next station after a certain time - the takt time. The time needed to complete work on each station has to be less than the takt time in order for the product to be completed within the allotted time.
Takt time concept aims to match the pace of production with customer demand.
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Definition
Takt time can be first determined with the formula:
Where
T = Takt time, e.g. [minutes of work / unit produced]
Ta = Net time available to work, e.g. [minutes of work / day]
Td = Time demand (customer demand), e.g. [units required / day]
Net available time is the amount of time available for work to be done. This excludes break times and any expected stoppage time (for example scheduled maintenance, team briefings, etc.).
Example:
If there is a total of 8 hours (or 480 minutes) in a shift (gross time) less 30 minutes lunch, 30 minutes for breaks (2 × 15 mins), 10 minutes for a team briefing and 10 minutes for basic maintenance checks, then the net Available Time to Work = 480 - 30 - 30 - 10 - 10 = 400 minutes. If customer demand was, say, 400 units a day and one shift was being run, then the line would be required to spend a maximum of one minute to make a part in order to be able to keep up with Customer Demand.
In reality, people and machines can never maintain 100% efficiency and there may also be stoppages for other reasons. Allowances should be made for these instances and thus the line will need to be set up to run at a faster rate to account for this.
Also, takt time may be adjusted according to requirements within the company. For example, if one department delivers parts to several manufacturing lines, it often makes sense to use similar takt times on all lines to smooth out flow from the preceding station. Customer demand can still be met by adjusting daily working time, reducing down times on machines and so on.
Implementation
Takt time is calculated on virtually every task in a business environment. It is used in manufacturing (casting of parts, drilling holes or preparing a workplace for another task), control tasks (testing of parts or adjusting machinery) or in administration (answering standard inquiries or call center operation). It is, however, most common in production lines that move a product along a line of stations that each perform a set of predefined tasks.
Once a takt system is implemented there are a number of benefits:
- The product moves along a line, so bottlenecks (stations that need more time than planned) are easily identified when the product does not move on in time.
- Correspondingly, stations that don't operate reliably (suffer frequent breakdown, etc.) are easily identified.
- The takt leaves only a certain amount of time to perform the actual value added work. Therefore there is a strong motivation to get rid of all non value-adding tasks (like machine set-up, gathering of tools, transporting products, etc.)
- Workers and machines perform sets of similar tasks, so they don't have to adapt to new processes every day, increasing their productivity.
- As all products are "stuck" in the line and cannot leave it, they cannot be "lost" somewhere on the shop floor.
Downsides of takt time organization include:
- When customer demand rises so much that takt time has to come down, quite a few tasks have to be either reorganized to take even less time to fit into the shorter takt time, or they have to be split up between two stations (which means another station has to be squeezed into the line and workers have to adapt to the new setup)
- When one station in the line breaks down for whatever reason the whole line comes to a grinding halt, unless there are buffer capacities for preceding stations to get rid of their products and following stations to feed from. A built-in buffer of three to five percent downtime allows needed adjustments or recovery from failures.[1]
- Small takt time can put considerable stress on workers and machines, increasing breakdowns and lowering motivation to the point of absenteeism.
- Tasks have to be leveled to make sure tasks don't bulk in front of certain stations due to peaks in workload. This decreases the flexibility of the system as a whole.
See also
External links
References
Further reading
- Ortiz, Chris A. (2006). "Takt Time". Kaizen assembly: designing, constructing, and managing a lean assembly line. Boca Raton: CRC Press. p. 48. ISBN 978-0-8493-7187-5. http://books.google.com/books?id=61Wr87UGAFAC&pg=PA48.