GMS 401 Chapter Notes - Chapter 10: Safety Stock, Taiichi Ohno, Takt Time
28 Jun 2018
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GMS – Chapter 10 – Just in Time and Lean Production
Just in Time (JIT) – production system in which processing and movement of
parts/modules/work in process occur just as they are needed, usually in small batches
Identical to lean production – JIT in a broad sense, is a philosophy of waste reduction and
continuous improvement
The JIT approach was developed at the Toyota Motor Company by Taiichi Ohno in Japan
The goals of lean production
Elimination of disruptions
System flexibility
Elimination of waste
Continuous improvement
Product quality is crucial to JIT/lean systems because poor quality can create major disruptions
In a balanced systems workload is distributed evenly among workstations
Takt time – the maximum time allowed at each workstation to complete its set of tasks on a
unit. Also call cycle time
Procedure for obtaining takt time:
1. Determine the net time available per shift by subtracting any non-productive time from
total shift time
2. If there is more than one shift per day, multiply the net time per shift by number of
shifts to obtain the net available time per day
3. Calculate takt time by dividing the net available time by demand during the day
Takt time = net time available per day / daily demand
Small lots decrease the size of work in process which reduces holding cost, space requirement
and clutter, inspection and rework costs are less when problems with quality occur. Small lots
mean greater system flexibility. Reduced inventory, increased visibility of problems, ease of
balancing operations
Single minute exchange of die (SMED) – a system for reducing change over time
Categorizes activities as internal or external
Many JIT systems have one or more cells. A cell contains the machine and tools needed to
process a family of parts that have similar processing requirement
Poka yoke – any mechanism that helps an equipment operator avoid mistakes. Its purpose is to
eliminate product defects by preventing, correcting or drawing attention to human errors as
they occur
Autonomation – intelligent automation; if an abnormal situation arises, the machine
automatically stops, preventing production of defective products
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