This article relies largely or entirely on a single source. (October 2010)
Takt time is a manufacturing term to describe the required product assembly duration that is needed to match the demand. It is the average time interval between the start of production of one unit and the start of production of the next unit, when items are produced sequentially. The takt time is based on customer demand; if a process or a production line are unable to produce at takt time, either demand leveling, additional resources, or process re-engineering is needed to ensure on time delivery.
For example, if the customer demand is 10 units per week, then, given a 40-hour work week and steady flow through the production line, the average duration between production starts should be 4 hours, ideally. This interval is further reduced to account for things like machine downtime and scheduled employee breaks.
Takt time is a borrowing of the Japanese word takuto taimu (タクトタイム), which in turn was borrowed from the German word Taktzeit, meaning 'cycle time'. The word was likely introduced to Japan by German engineers in the 1930s.
Assuming a product is made one unit at a time at a constant rate during the net available work time, the takt time is the amount of time that must elapse between two consecutive unit completions in order to meet the demand.
Takt time can be first determined with the formula:
T = Takt time, e.g. [work time between two consecutive units]
Ta = Net time available to work, e.g. [work time per period]
D = Demand (customer demand), e.g. [units required per period]
If there are 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 were 400 units a day and one shift were being run, then the line would be required to output at a minimum rate of one part per minute in order to be able to keep up with customer demand.
Takt time may be adjusted according to requirements within a 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.
Some of the early[when?] literature uses cycle time for takt time.
Takt time is calculated on every task: it is common in production lines that move a product along a line of stations that each performs a set of predefined tasks.
- Manufacturing: casting of parts, drilling holes, or preparing a workplace for another task
- Control tasks: testing of parts or adjusting machinery
- Administration: answering standard inquiries or call center operation
Benefits of takt time
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.
- There is no place in the takt system for removal of a product from the assembly line at any point before completion, so opportunities for shrink and damage in transit are minimized.
Problems of takt time
Once a takt system is implemented there are a number of problems:
- 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.
- Short takt time can put considerable stress on the "moving parts" of a production system or subsystem. In automated systems/subsystems, increased mechanical stress increases the likelihood of breakdown, and in non-automated systems/subsystems, personnel face both increased physical stress (which increases the risk of repetitive motion (also "stress or "strain") injury), intensified emotional stress, and lowered motivation, sometimes to the point of increased 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.
- The concept of takt time doesn't account for human factors such as an operator needing an unexpected bathroom break or a brief rest period between units (especially for processes involving significant physical labor). In practice, this means that the production processes must be realistically capable of operation above peak takt and demand must be leveled in order to avoid wasted line capacity
- Lean Manufacturing site about Takt time
- Six Sigma site about Takt time
- Takt Time Simulator On Line
- On Line business processes simulator
- Takt Time - a vision for Lean Manufacturing
- Monden, Yasuhiro (2011). Toyota Production System: An Integrated Approach to Just-In-Time. New York: Productivity Press. p. 566. ISBN 1-4398-2097-X.
- Ohno, Taiichi, Toyota Production System: Beyond Large-Scale Production, Productivity Press (1988). ISBN 0-915299-14-3
- Baudin, Michel, Lean Assembly: The Nuts and Bolts of Making Assembly Operations Flow, Productivity Press (2002). ISBN 1-56327-263-6
- Ortiz, Chris A., Kaizen Assembly: Designing, Constructing, and Managing a Lean Assembly Line, CRC Press. ISBN 978-0-8493-7187-5