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Chapter 8 - Lean Operations & The Toyota Production System

Terms in this set (38)

"Lean"
Reflects the operation's goal to eliminate waste from the system.
(coined by James Womack)
used interchangeable with "TPS"
Waste of Time at a Resource
The waste of time from the perspective of a resource, which reduces the capacity of the resource.
(capacity is wasted because of Idle Time)
Waste of Time of a Flow Unit
The waste of time from the perspective of a flow unit, which makes the flow time of that flow unit longer than what is needed in the eyes of the customer.
Toyota Production System (TPS)
A framework used to run operations with the goal of reducing both the waste of capacity and the waste of flow time, thereby making sure supply and demand are matched just in time.
used interchangeably with "lean"
Fredrick Winslow Taylor
Seen as the father of Operations Management
Taiichi Ohno
~Founder of TPS
~Focused on:
1. Waste
2. Work (non-value added & value added work)
Waste/Muda
The needless waste of time and worker movements that ought to be eliminated immediately.
~Ex: idle time/fixing broken units
~Ex: do not add value to the customer
Non-Value Added Work
Movements that do not add value in the eyes of the customer but must be done under the current conditions of the process in order to complete a unit.
~Ex: worker moving from one machine to another
Value-Added Work
Movements valued by the customer as they are absolutely required to transform the flow unit from its inputs to being the output the customer wants.
Total Available Time
The amount of time a resource has available to fulfill demand.
Overall Equipment Effectiveness (OEE)
The percentage of total available time that is used in a way that adds value to the customer.
Overall Equipment Effectiveness (OEE) (Equation)
= Value-Added Time/Total Available Time
Genchi Genbutsu
means to "go and see in the real place"
Kaizen
Process improvement
7 Sources of Production Waste
1. Waiting (time-on-hand) - waiting for inputs from previous step, waiting for machine to complete it's job.
2. Overproduction - just-in-time production, producing too much too soon will waste capacity.
3. Inventory - result of over-production/supply-demand mismatch
4. Transport - processes should be laid out so the physical layout reflects the process flow to minimize the distances flow units must travel through a process
5. Over-Processing/Incorrect Processing - workers often spend more time on a flow unit than necessary
6. Rework - "do it right the first time", rework requires repeating an operation (takes time away from regular production)
7. Unnecessary Motions & Movements - there are many ways to perform a task but there is only one "right way" which everyone should follow
8th Source of Waste
Waste of Worker Intellect
Wasting Time of Flow Unit (2 approaches)
1. Taking Perspective of Flow Unit - create simple timeline and document what the flow unit is doing at each moment in time it journeys through the process
2. Looking at Inventory - (Little's Law), as long as we hold flow rate constant, flow time is proportional to amount of inventory in the process (instead of looking for flow time, look for inventory)
Value-Added Percentage (Equation)
= Value-Added Time of Flow Unit/Flow Time
(value-added time of flow unit is related to labor content)
4 P's of Toyota
1. Philosophy - long-term approach, favors quality & capability
2. Processes - continuous flow, match supply & demand, reduce waste
3. People/Partners - respectful interaction with employees & partners
4. Problem Solving - ongoing improvement of operations
Smooth Flow
Steady and even pace is better than bursts of speed followed by periods of no movement. (recall Takt Time)
Single-Unit Flow
Operate at a flow of one unit at a time from one resource to the next instead of operating based on transfer batches.
Ways Single-Unit Flow Exposes & Reduces Waste
1. Less inventory - reduce finished goods and work-in-progress inventory
2. Shorter response times to demand - shorter flow times
3. Faster feedback - on defective unit if it moves to next station faster
4. Simpler and more flexible staffing - just to produce to demand
5. Shorter processing times - workers slow down with buffer times
6. More transparency - with lower inventory, imbalances & defects are easier to spot
Pull System
The resource furthest downstream is paced by market demand. In addition to its own production, it also relays the demand information to the next station upstream, ensuring upstream resource is also paced by demand. It is in an operating system in which the production or replenishment of a unit is only initiated when a demand occurs.
(2 forms of process control are Kanban & Make-to-Order)
Kanban
Upstream resource replenishes what demand has withdrawn from the downstream resource.
~best used for products/parts that are processed in high volume & limited variety
~compromise between traditional push system and ideal case of a single-unit flow
Make-to-Order
Release of work into a system only when a customer order has been received for that unit.
~best used for products/parts that are processed in low volume & high variety. (customers are willing to wait) (expensive/difficult to sore flow units)
Number of Kanban Cards (Equation)
= (Demand During Replenishment Time + Safety Stock)/Container Size
Demand During Replenishment Time (Equation)
= Replenishment Time x Demand Rate
Process Layout
The spatial location of resources in a process that drives the needs for transportation.
1. Organize work stations matching flow of materials
2. Create Baton Passing Zones - instead of having fixed allocations of activities to workers, the process can absorb variations in speed and starting time
3. Use U-Shaped Lines - locating resources in a way that they create a "U" shape, increases flexibility of workers to perform multiple tasks.
Takt Time
Idea is to staff according to demand, when demand goes down, so does Target Manpower. Needs a workforce of highly skilled, full-time employees & temporary workers (for periods of high demand)
Demand Leveling
A way to sequence flow units so that the work flow causes a stable work load for all workers involved in the process.
3 M's Enemies of Lean Operation
1. Mura - unevenness in flow
2. Muri - unreasonable amount of work, over-burdening a machine/operator
3. Muda - waste
Heijunka
(Production leveling) - reducing variation in work schedule that arises from demand variation or desire to run production in large batches.
production to match true rate of demand
Detect-Stop-Alert (Jidoka)
1. Jidoka - upon detection of a problem, shutting down the machine to force a human intervention, which in turn triggers process improvement
2. Kaizen - thoroughly analyzing root cause on shop floor
3. Poka-Yoke - avoiding recurrence of problem by implementing improvements
Exposing/Solving Problems
exposing problems is critical and inventory acts as cover-up for problems (which is a problem)
Autonomation
Automation with a human touch; use machines, but combine them with the intelligence of workers.
Andon
Cord that enables workers to stop production because of defect
Information Turnaround Time (ITAT)
Time between creating a defect and receiving feedback about the defect.
Root-Cause Problem Solving & Detection Prevention
1. Kaizen - process of making small changes to the process with goal of eliminating waste (continuous improvement)
2. Genchi Genbutsu - gather 1st hand info from situation by going and observing situation yourself, collecting & analyzing data (important philosophy behind Kaizen)
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