A Fundamental Principle of TPS
Produce to Demand
1. Make only what is needed when it is needed.
2. Base production and planning on Takt Time.
3. Develop flexible production lines. When demand changes,
the line changes. Usually, labor changes to maintain labor
efficiency.
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Produce to Demand…Takt Time
1. Takt Time is the pace at which the customer is buying a particular
product.
2. Takt time is not how long it takes to perform a task. It is customer
demand, not cycle time.
3. Takt time is calculated by taking the available time to work and dividing
it by the demand for that period of time
4. Takt time cannot be reduced or increased except by a change in sales
or the available time to work
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Takt Time Formula
Productive Time Available per period
Number of Required Units per period
Example: Productive Time Available Calculation
Time available per Shift (8 hours)
480 minutes
Breaks (2 at 10 minutes each)
-20 minutes
Lunch
-20 minutes
Productive Time Available
=
440 minutes or 26,400 seconds
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Takt Time Formula
Productive Time Available per period
Number of Required Units per period
Example: Number of Required Units Calculation
Units = 72,000 units ordered per month = 1,200 Units Required per Shift
60 shifts per month (3 shifts x 20 days)
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Takt Time Formula
Productive Time Available per period
Number of Required Units per period
Example: Takt Time Calculation
Takt Time =
26,400 seconds available per shift
= 22 seconds / unit
1,200 units required per shift
So…the line should make one unit every 22 seconds to meet
customer demand.
5
Number of Operators Required Formula
Sum of Manual Cycle Time
Takt Time
Example: Operators Required Calculation
123 seconds
= 5.59 or 6 operators required
22 seconds
6
Labor Efficiency Formula
(Sum of Manual Cycle Time / 3600seconds per hour) x Demand per Shift
x100
Current Manning x Available Hours per Shift
Example: Variables
Total manual time to make one unit
123 seconds
Demand per shift
1,200 units
Current Manning
7 direct operators
Available hours per shift
7.3 hours (440 minutes)
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Labor Efficiency Formula
(Sum of Manual Cycle Time / 3600 seconds per hour) x Demand per Shift
x100
Current Manning x Available Hours per Shift
Example: Labor Efficiency Calculation
(123 seconds / 3600 seconds) x 1,200 units per shift
7 operators x 7.3 hours per shift
x100
= 70% labor efficiency
8
Line Capacity Formula
Productive Time Available (seconds)
Bottleneck Station Cycle Time* (seconds)
Example: Capacity Calculation
26,400 seconds per shift
=
1,553 unit capacity per shift
17 second cycle time bottleneck station*
*Bottleneck Station Cycle Time = Machine C/T + Manual Load / Unload C/T
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Performance to Capacity Formula
Actual Line Output (units)
x100
Line Capacity (units)
Example: Performance to Capacity Calculation
1,200 units per shift
x 100
= 77%
1,553 units per shift
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Operational Availability (Formal TPS Definition)
Actual Output (units)
x100
Demand (units)
Examples: Operational Availability Calculation
1,080 units per shift
1,200 units per shift
under-production
x100
= 90%
1450 units per shift
x100
= 120%
1200 units per shift
over-production
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Rate of Operation Formula
Demand (units)
x100
Capacity (units)
Examples: Rate of Operation Calculation
1,200 units per shift
x100
= 77%
1,553 units per shift
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