When is Lean too Lean Discrete Event Simulation

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When is Lean too Lean: Discrete Event Simulation and Lean Production Scott Metlen

When is Lean too Lean: Discrete Event Simulation and Lean Production Scott Metlen

‘Romantic’ Lean & Complex Systems • Strategic variability leading to complex systems • Complex

‘Romantic’ Lean & Complex Systems • Strategic variability leading to complex systems • Complex system modeling (use discrete event simulation)

Waste by Ohno, 1988 • • Overproduction Transportation Inventory Motion Defective Product Over-processing Waiting

Waste by Ohno, 1988 • • Overproduction Transportation Inventory Motion Defective Product Over-processing Waiting

Discrete Event Simulation (DES) • Modeling events of a system where time between events

Discrete Event Simulation (DES) • Modeling events of a system where time between events is stochastic. • To expensive to use in deterministic systems

System Variation, the Cause of Waste • Dysfunctional Variability (Suri, 2005) – Inconsistent process

System Variation, the Cause of Waste • Dysfunctional Variability (Suri, 2005) – Inconsistent process times when product is consistent – Set up times vary when product does not – Raw material varies when it should be consistent – Inconsistency of human performance • Strategic Variability (Suri, 2005) – Mass customization due to market demand – Willing to chase spikes and valleys in demand

Danger of Lean • Eliminating strategic variation along with dysfunctional variability in the quest

Danger of Lean • Eliminating strategic variation along with dysfunctional variability in the quest to eliminate waste • Prevent by simulating system change to determine the affect on profit if the change were executed

Example • 875 parts used to assemble 10 products • Parts for each product

Example • 875 parts used to assemble 10 products • Parts for each product collected as a ‘kit’ • 875 parts had different paths through the production system, scheduling was complex, average scrap rate 2% (complexity of parts and system) • FG warehouse kept to make sure each ‘kit’ was shipped on time and complete • FG seen as waste, was eliminated and replaced by expediting system to make sure a ‘kit’ shipped on time

Results • Overtime went to $15 million • More production was installed where FG

Results • Overtime went to $15 million • More production was installed where FG used to be • $200, 000. 00 opportunity cost saved on not having FG inventory • On time delivery dropped • Scrap rate increased

New Solution Modeled • • • Modeled Strategic FG inventory $100000 opportunity cost Overtime

New Solution Modeled • • • Modeled Strategic FG inventory $100000 opportunity cost Overtime reduced by $7 million On time delivery reestablished Scrap rate reduced Recommendation was implemented, savings as indicated

Take Away • In complex systems using strategic variability, model system before changing that

Take Away • In complex systems using strategic variability, model system before changing that system • QUESTIONS