Chapter 4: From the JIT Revolution to Lean Manufacturing Chapter 5: What Went Wrong?TM 663 Operations Planning September 26, 2011 Paula JensenAgenda Airplanes Factory Physics Chapter 4: From the JIT Revolution to Lean Chapter 5: What Went Wrong (New Assignment Chapter 4 Study Questions: 4,5,6,7 Chapter 5 Study Questions: 2,3,4,6 )Just In Time (JIT)I tip my hat to the new constitution Take a bow for the new revolution Smile and grin at the change all around Pick up my guitar and play Just like yesterday Then I get on my knees and pray WE DONT GET FOOLED AGAIN!The WhoOrigins of JIT Japanese firms, particularly Toyota, in 1970s and 1980s Taiichi Ohno and Shigeo Shingo Geographical and cultural roots Japanese objectives “catch up with America” (within 3 years of 1945) small lots of many models Japanese motivation Japanese domestic production in 1949 25,622 trucks, 1,008 cars American to Japanese productivity ratio 9:1 Era of “slow growth” in 1970sToyota Production System Pillars: 1. just-in-time, and 2. autonomation, or automation with a human touch Practices: setup reduction (SMED) worker training vendor relations quality control foolproofing (baka-yoke) many othersSupermarket Stimulus Customers get only what they need Stock replenished quickly But, who holds inventory?Auto-Activated Loom Stimulus Automatically detect problems and shut down Foolproofing Automation with a human touchZero Inventories Metaphorical Writing:The Toyota production wrings water out of towels that are already dry.There is nothing more important than planting “trees of will”. Shingo 19905W = 1H Ohno 1988 Platonic Ideal:Zero Inventories connotes a level of perfection not ever attainable in a production process. However, the concept of a high level of excellence is important because it stimulates a quest for constant improvement through imaginative attention to both the overall task and to the minute details. Hall 1983The Seven Zeros Zero Defects: To avoid delays due to defects. (Quality at the source) Zero (Excess) Lot Size: To avoid “waiting inventory” delays. (Usually stated as a lot size of one.) Zero Setups: To minimize setup delay and facilitate small lot sizes. Zero Breakdowns: To avoid stopping tightly coupled line. Zero (Excess) Handling: To promote flow of parts. Zero Lead Time: To ensure rapid replenishment of parts (very close to the core of the zero inventories objective). Zero Surging: Necessary in system without WIP buffers.The Environment as a Control Constraints or Controls? machine setup times vendor deliveries quality levels (scrap, rework) production schedule (e.g. customer due dates) product designs Impact: the manufacturing system can be made much easier to manage by improving the environment.Implementing JIT Production Smoothing: relatively constant volumes relatively constant product mix Mixed Model Production (heijunka): 10,000 per month (20 working days) 500 per day (2 shifts) 250 per shift (480 minutes) 1 unit every 1.92 minutesImplementing JIT (cont.) Production Sequence: Mix of 50% A, 25% B, 25% C in daily production of 500 units0.5 500 = 250 units of A 0.25 500 = 125 units of B 0.25 500 = 125 units of C A B A C A B A C A B A C A B A C Inherent Inflexibility of JIT Sources of Inflexibility: Stable volume Stable mix Precise sequence Rapid (instant?) replenishment Measures to Promote Flexibility: Capacity buffers Setup reduction Cross training Plant layoutCapacity Buffers Problems: JIT is intrinsically rigid (volume, mix, sequence) No explicit link between production and customers How to deal with quota shortfalls Buffer Capacity: Protection against quota shortfalls Regular flow allows matching against customer demands Two shifting: 4 8 4 8 Contrast with WIP buffers found in MRP systemsSetup Reduction Motivation: Small lot sequences not feasible with large setups. Internal vs. External Setups: External performed while machine is still running Internal performed while machine is down Approach: 1. Separate the internal setup from the external setup 2. Convert as much as possible of the internal setup to the external setup 3. Eliminate the adjustment process 4. Abolish the setup itself (e.g., uniform product design, combined production, parallel machines)Cross Training Adds flexibility to inherently inflexible system Allows capacity to float to smooth flow Reduces boredom Fosters appreciation for overall picture Increase potential for idea generationWorkforce Agility Cross-Trained Workers: float where needed appreciate line-wide perspective provide more heads per problem area Shared Tasks: can be done by adjacent stations reduces variability in tasks, and hence line stoppages/quality problemsPlant Layout Promote flow with little WIP Facilitate workers staffing