Chapter 4: Lean Systems

Question 1

Lean systems

Answer 1

Operations systems that maximize value added by each of a company’s activities by removing waste and delays from them

Encompass the entirety of a company’s operations

Question 2

Just in time system

Answer 2

JIT

A key foundation of a lean system. Represents a collection of practices that eliminate waste (aka muda) by cutting excess capacity or inventory and removing non-value-added activities

Question 3

Eight types of waste

Answer 3

1. Overproduction
2. Inappropriate processing
3. Waiting
4. Transportation (excessive movement/ material handing)
5. Unnecessary Motion
6. Excess Inventory
7. Defects
8. Underutilization of employees

Question 4

Goal of lean systems

Answer 4

To eliminate the eight types of waste
Produce services and products only as needed
Continuously improve value-added benefits of operations

Question 5

Kaizen

Answer 5

Japanese, means “change for the better”

An approach to process improvement that centers the understanding that excess capacity/inventory hides underlying problems in a process. Excess capacity/inventory is removed to better spotlight areas for improvement

often uses “PDCA” process (plan, do, check, act)

Question 6

Techniques to identify areas for continuous improvement

Answer 6

-maintaining low inventories
- periodically stressing the system
- focusing on the elements of the lean system

Question 7

Supply chain considerations in lean systems

Answer 7

• close supplier ties
• small lot sizes

Question 8

JIT II system

Answer 8

Aka vendor-managed inventories

Supplier is brought into the plant to be an active member of the purchasing office of the customer, empowered to plan and schedule replenishment of their materials

Fosters an extremely close interaction with suppliers

Question 9

Benefits of small lot sizes

Answer 9

• reduces average inventory level
• inventory moves faster
• if defect discovered, less items to inspect
• helps maintain uniform workload and prevent overproduction
• makes it easier to rearrange workflow order

Question 10

Disadvantages of small lot sizes

Answer 10

Increased setup frequency

Question 11

Single digit setup

Answer 11

The goal of having a setup time of less than 10 minutes

Question 12

Process considerations in lean systems

Answer 12

• pull method of workflow
• quality at the source
• uniform workstation loads
• standardized components and work methods
• flexible workforce
• automation
• five S (5S) practices
• total productive (preventative) maintenance (TPM)

Question 13

Pull method of material flows

Answer 13

A method in which customer demand activated the production of a service or item

Commonly used in lean operations

Question 14

Push method of material flows

Answer 14

A method in which production of the item begins in advance of customer needs

Dependant on forecasting

Question 15

Quality at the source

Answer 15

A philosophy whereby defects are caught and corrected where they are created.

Goal for workers to act as their own quality inspectors and never pass defective units to the next process

Question 16

Jidoka

Answer 16

A visual management system that Automatically stops the process when something is wrong and then fixing the problems on the line itself as they occur

Separates worker and machine activities by freeing workers from tending to machines constantly, allowing a single worker to staff multiple operations simultaneously

Question 17

Poka-yoke

Answer 17

Mistake-proofing methods aimed at designing fail-safe systems that minimize human error

Question 18

Andon

Answer 18

A system that gives machines and machine operations the ability to signal the occurrence of any abnormal conditions

Question 19

Ways to achieve uniform workstation load

Answer 19

• reservations for service processes
• differential pricing to manage demand
• scheduling to same daily workload for manufacturing (capacity planning –>master production schedule –> daily workload)

Question 20

Takt time

Answer 20

Cycle time of a process needed to match the rate of production to the rate of sales or consumption

Question 21

Heijunka

Answer 21

Leveling of production load by both volume and product mix.

Instead of building to actual flow of orders builds to overall demand leveled out so same amount being made each day

Question 22

Mixed- model assembly

Answer 22

A type of assembly that produces a mix of models in smaller lots

Question 23

Five S (5S)

Answer 23

A methodology consisting of five workplace practices:
- sorting
- straightening
- shining
- standardizing
- sustaining

Conducive to visual controls and lean production

Enabler/foundation of lean systems

Question 24

Why are line flows recommended for designing lean systems layouts?

Answer 24

• eliminate waste
• reduced frequency of setups (if volume is large enough setups may be eliminated entirely)

Question 25

One-worker, multiple-machines cell

Answer 25

OWMM A one person cell in which a worker operates several different machines simultaneously to achieve a line flow. Some tasks are automated and operator performs non-automated tasks Reduces inventory queues and overall labor needed Used when volumes are insufficient to keep multiple line workers busy

Question 26

Group technology

Answer 26

GT An option for achieving line-flow layouts with low volume processes; technique creates cells not limited to just one worker and has a unique way of selecting work to be done by the cell Groups part or products with similar characteristics/processing requirements in families and sets aside groups of machines for their production (minimizes setup)

Question 27

Kanban

Answer 27

A Japanese word meaning "card" or "visible record" that refers to the cards used to control the flow of the production through the factory Goal to ensure company has minimum amount of inventory to keep production running and that production is being pulled by customer demand

Question 28

Basic kanban system

Answer 28

- card attached to each container of items produced - each container holds a given percent of the daily production requirement of that item - when container is emptied card is moved to a receiving post, signalling the need to produce another container of the part - when container refilled the card is out back on the container

Question 29

General operating rules of the kanban system

Answer 29

Designed to facilitate flow and maintain control of inventory levels - a full container must always have a kanban card - the preceding process will never produce parts without a kanban card - the following process must post the kanban card at the receiving post before beginning consumption of the parts inside the containers - the containers should always be standard and contain the same number of good parts (described on the kanban card) - only non-defective parts should be put into inventory with the kanban card (quality at the source)

Question 30

Little's law

Answer 30

Average inventory = average demand rate x average demand time

Question 31

How to determine the number of containers in a kanban system

Answer 31

# of containers = ((expected daily demand for units)*(fraction of the day spent in materials handling and waiting during the production process+ fraction of a day it takes to process each container)*(1+ variable set by policy for safety stock)) / quantity of units in a standard container

Question 32

Average lead time per container (kanban system)

Answer 32

= waiting and materials handling time + production time May be decreased by improved operations

Question 33

Alternate Kanban signals

Answer 33

- the empty container itself - in a container less system a painted area in a workbench

Question 34

Value stream mapping

Answer 34

VSM A qualitative lean tool for eliminating waste (muda) that involves a current state drawing, a future state drawing and an implementation plan Visual mapping of every process involved in materials and information flows in a products value stream

Question 35

Steps of building a future state map

Answer 35

1) determine if the process steps are capable of producing according to required takt time (if not apply constraint management methods) 2) identify where in the value stream inventories may be eliminated (creation of cell) 3) design pull systems to manage remaining inventories 4) preparing and using implementation plan to achieve the future state

Question 36

Organizational considerations for lean systems

Answer 36

- potential for workers to feel stressed and like they have lost autonomy - importance of cooperation and trust between teams, workforce and management - realignment of reward system may be difficult given labor contracts

Question 37

Process considerations for moving to lean systems

Answer 37

Need to change existing layout can be expensive

Question 38

Inventory and scheduling considerations for lean systems

Answer 38

- lean systems require schedule stability and do not respond quickly to scheduling changes (in high volume environments) - small lot sizes require a large number of set ups at significantly reduced times. Not flexible for sudden changes in set up time - low levels of raw materials inventory requires reliable ordering/shipping/receiving (recovery may be difficult after supply chains are disrupted)

Question 39

what is waste?

Answer 39

An activity that adds cost or time but does not add value consuming more resources than are necessary to produce the goods or services that the customer wants

Question 40

Two types of waste

Answer 40

- Pure Waste - incidental waste

Question 41

Pure waste

Answer 41

"actions that could be stopped without affecting the customer (waste in processing that the customer never sees)

Question 42

Incidental waste

Answer 42

Actions that need to be done based on how the current system operations that do not add value. Somehow inherent to the system and require a change to the whole system to fix them

Question 43

Ryder Systems lean guiding principles

Answer 43

- people involvement (making use of employee knowledge) - built-in quality - standardization (document and follow best practices) - short lead time - continuous improvident

Question 44

Characteristics of lean employees

Answer 44

- persist when confronted with difficulties - adapt, are proactive and thrive under uncertainty - take personal initiative - understand what's important at the moment and take appropriate action - are deeply engaged with the organization

Question 45

How to foster people involvement in a lean organization

Answer 45

- focus on communication - empower the experts (people who do the work) - cross training so people understand the whole process

Question 46

What is built-in-quality

Answer 46

a focus on getting it right the first time benefits the entire process mistake-proofing to eliminate rework

Question 47

FMEA

Answer 47

Failure mode and effects analysis testing where the tester tries to break/ find the weak points of a process so they know what needs fixing

Question 48

Why is standardization important to lean systems

Answer 48

everyone follows best practices so improvements multiply and are more sustainable

Question 49

layered audit

Answer 49

Audit performed while the work is in progress to allow for immediate corrections of errors

Question 50

visual management

Answer 50

visual tools to communicate with employees

Question 51

ways to shorten lead time

Answer 51

- streamlining work - eliminating steps that do not add value - keep work flowing without impediment or waste

Question 52

Elements that facilitate shorter lead time

Answer 52

- small lots - level loading - simple process flows - pull system

Question 53

implementing simple process flows

Answer 53

use Value Stream Mapping to break process down into its smallest step, diagram, and identify waste points to remove waste/ simplify flow

Question 54

Level loading

Answer 54

work is structured so that pace and momentum stays steady throughout the process important to keep processes in sync ideally paced to meet customer demand

Question 55

Pull system

Answer 55

customer consumption creates the signal that determines how much inventory to replenish, so system matches how demand changes

Question 56

Continuous Improvement

Answer 56

based on the Idea that it is more effective to make many small gains over time rather than try to accomplish massive gains all at once uses structured problem solving of identifying a problem, analyzing its root causes, and implenting solutions

Question 57

Five Whys tool

Answer 57

Used to walk backwards through a problem to discover the flaw that created the problem. The idea being that if you ask "why" five times you will get to the root of an issue

Question 58

use of automation in lean systems

Answer 58

have humans focus on high-value complex work and use automation to support these tasks by automating the basic, repetitive, low-value steps

Question 59

Standard work

Answer 59

combines the elements of a job into the most effective sequence without waste to achieve the most efficient level of production simplifies finding anomalies where the process deviates from standard

Question 60

Andon cord

Answer 60

a way to empower front-line workers to address quality (or other) problems by stopping production until the defect is fixed. (to avoid problems compounding)

Question 61

Six sigma

Answer 61

a statistical measure of defect - out of one million opportunities for defect how many defects occur (a non-linear function) offers a way to compare across different processes 3- 4 sigma is average, 6 sigma is considered "best in class

Question 62

sigma rage of average company/ person

Answer 62

3-4 sigma range

Question 63

Six sigma textbook definition

Answer 63

a comprehensive and flexible system for achieving, sustaining, and maximizing business success by minimizing defects and variability in processes

Question 64

Opportunities for defect

Answer 64

number of possible way for an item or process to be defective * number of times item or process is produced

Question 65

defect (for purpose of six sigma)

Answer 65

any time a product or service does not meet the customer expectation

Question 66

A six sigma process

Answer 66

one that eliminates the opportunities for defects

Question 67

variability and sigma

Answer 67

a process with a higher variability will have a lower sigma - more defects per million opportunities. If can improve standardization can reduce variation and increase sigma

Question 68

5S

Answer 68

a theory that focuses on effective workplace organization and standardization that allows people to easily spot variation from standard operating conditions - sort - stabilize (simplify or set in order) - shine (regular cleaning and maintenance) - standardize (develop a system) - sustain (maintain the system)