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Operations Management > Chapter 4: Lean Systems > Flashcards

Chapter 4: Lean Systems Flashcards

1
Q

Lean systems

A

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

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2
Q

Just in time system

A

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

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3
Q

Eight types of waste

A
  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
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4
Q

Goal of lean systems

A

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

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5
Q

Kaizen

A

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)

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6
Q

Techniques to identify areas for continuous improvement

A

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

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7
Q

Supply chain considerations in lean systems

A
  • close supplier ties
  • small lot sizes
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8
Q

JIT II system

A

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

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9
Q

Benefits of small lot sizes

A
  • 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
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10
Q

Disadvantages of small lot sizes

A

Increased setup frequency

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11
Q

Single digit setup

A

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

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12
Q

Process considerations in lean systems

A
  • 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)
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13
Q

Pull method of material flows

A

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

Commonly used in lean operations

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14
Q

Push method of material flows

A

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

Dependant on forecasting

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15
Q

Quality at the source

A

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

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16
Q

Jidoka

A

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

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17
Q

Poka-yoke

A

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

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18
Q

Andon

A

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

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19
Q

Ways to achieve uniform workstation load

A
  • reservations for service processes
  • differential pricing to manage demand
  • scheduling to same daily workload for manufacturing (capacity planning –>master production schedule –> daily workload)
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20
Q

Takt time

A

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

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21
Q

Heijunka

A

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

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22
Q

Mixed- model assembly

A

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

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23
Q

Five S (5S)

A

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

Conducive to visual controls and lean production

Enabler/foundation of lean systems

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24
Q

Why are line flows recommended for designing lean systems layouts?

A
  • eliminate waste
  • reduced frequency of setups (if volume is large enough setups may be eliminated entirely)
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25
Q

One-worker, multiple-machines cell

A

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

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26
Q

Group technology

A

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)

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27
Q

Kanban

A

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

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28
Q

Basic kanban system

A
  • 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
29
Q

General operating rules of the kanban system

A

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)

30
Q

Little’s law

A

Average inventory = average demand rate x average demand time

31
Q

How to determine the number of containers in a kanban system

A

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

32
Q

Average lead time per container (kanban system)

A

= waiting and materials handling time + production time

May be decreased by improved operations

33
Q

Alternate Kanban signals

A
  • the empty container itself
  • in a container less system a painted area in a workbench
34
Q

Value stream mapping

A

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

35
Q

Steps of building a future state map

A

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

36
Q

Organizational considerations for lean systems

A
  • 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
37
Q

Process considerations for moving to lean systems

A

Need to change existing layout can be expensive

38
Q

Inventory and scheduling considerations for lean systems

A
  • 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)
39
Q

what is waste?

A

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

40
Q

Two types of waste

A
  • Pure Waste
  • incidental waste
41
Q

Pure waste

A

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

42
Q

Incidental waste

A

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

43
Q

Ryder Systems lean guiding principles

A
  • people involvement (making use of employee knowledge)
  • built-in quality
  • standardization (document and follow best practices)
  • short lead time
  • continuous improvident
44
Q

Characteristics of lean employees

A
  • 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
45
Q

How to foster people involvement in a lean organization

A
  • focus on communication
  • empower the experts (people who do the work)
  • cross training so people understand the whole process
46
Q

What is built-in-quality

A

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

47
Q

FMEA

A

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

48
Q

Why is standardization important to lean systems

A

everyone follows best practices so improvements multiply and are more sustainable

49
Q

layered audit

A

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

50
Q

visual management

A

visual tools to communicate with employees

51
Q

ways to shorten lead time

A
  • streamlining work
  • eliminating steps that do not add value
  • keep work flowing without impediment or waste
52
Q

Elements that facilitate shorter lead time

A
  • small lots
  • level loading
  • simple process flows
  • pull system
53
Q

implementing simple process flows

A

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

54
Q

Level loading

A

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

55
Q

Pull system

A

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

56
Q

Continuous Improvement

A

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

57
Q

Five Whys tool

A

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

58
Q

use of automation in lean systems

A

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

59
Q

Standard work

A

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

60
Q

Andon cord

A

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)

61
Q

Six sigma

A

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

62
Q

sigma rage of average company/ person

A

3-4 sigma range

63
Q

Six sigma textbook definition

A

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

64
Q

Opportunities for defect

A

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

65
Q

defect (for purpose of six sigma)

A

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

66
Q

A six sigma process

A

one that eliminates the opportunities for defects

67
Q

variability and sigma

A

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

68
Q

5S

A

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)

Operations Management (11 decks)

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