Material Handling and Storage System

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Material Handling and Storage System

• Functions of the Handling System
• Random, independent movement of workparts between
  stations.
• Handle a variety of workpart configurations.
• Temporary storage.
• Convenient access for loading and unloading
  workparts.
• Compatible with computer control.

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FMS Layout Configurations

• In-line layout
• Loop layout
• Ladder layout
• Open field layout
• Robot-centered cell

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Material Handling Equipment
The material handling function in a FMS is often
shared between two systems

• Primary handling system - establishes the basic
  layout of the FMS and is responsible for moving
  workparts between stations in the system.
• Secondary handling system - consists of transfer
  devices, automatic pallet changers, and similar
  mechanisms located at the workstations in the FMS.

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Equipment used as primary handling system
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Computer Control System

• Function performed by FMS computer control

• Workstation control.
• Distribution of control instructions to
  workstations.
• Production control.
• Traffic control. - Primary handling system

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Function performed by FMS computer control

• Shuttle control. Secondary handling system
• Workpiece monitoring.
• Tool control. - concerned with managing two
  aspects of the cutting tools (a) tool location,
  (b) tool life monitoring.
• Performance monitoring and reporting - see table.
• Diagnostics.

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Typical FMS performance reports
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Human Resources
Humans are needed to manage the operations of the
FMS. Functions typically performed by humans

• Loading raw workparts onto the system
• Unloading finished parts (or assemblies) from the
  system
• Changing and setting tools
• Equipment maintenance and repair
• NC part programming in a machining system
• Programming and operating the computer system
• Overall management of the system.

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FMS Benefits

• Increased machine utilization.
• FMSs achieve a higher average utilization than
  stand-alone machines in a conventional machine
  shop. Reasons include (1) 24 hour per day
  operation, (2) automatic tool changing at machine
  tools, (3) automatic pallet changing at
  workstations, (4) queues of parts at stations,
  and (5) dynamic scheduling of production that
  takes into account irregularities from normal
  operations. It should be possible to approach
  80 to 90 asset utilization.

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• Fewer machines required. Because of higher
  machine utilization.
• Reduction in factory floor space required.
  Compared to a job shop of equivalent capacity, a
  FMS generally requires less floor area.
  Reductions in floor space requirements 40 to
  50.
• Greater responsiveness to change. A FMS improves
  response capability to part design changes,
  introduction of new parts, changes in production
  schedule and product mix, machine breakdowns, and
  tool failures. Adjustments can be made in the
  production schedule from one day to the next to
  respond to rush orders and special customer
  requests.

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• Reduced inventory requirements. Because
  different parts are processed together rather
  than separately in batches, WIP is less than in
  batch production. Inventories of starting and
  finished parts reduced also. Reductions 60 to
  80.
• Lower manufacturing lead times. Closely
  correlated with lower WIP is MLT. This means
  faster customer deliveries.
• Reduced direct labor requirements and higher
  labor productivity. Savings 30 to 50
• Opportunity for unattended production.

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FMS Planning and Design Issues

• Part family considerations.
• The part family that will be processed on the
  FMS must be defined. Part families can be based
  on product commonality as well as part
  similarity. The term product commonality refers
  to different components used on the same product.
• Processing requirements.
• In machining applications, nonrotational parts
  are produced by machining centers, milling
  machines, and like machine tools rotational
  parts are machined by turning centers and similar
  equipment.

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FMS Planning and Design Issues(continued)

• Physical characteristics of the workparts.
• Part sizes and weights determine the size of
  the machines and the size of the material
  handling system.
• Production volume.
• The production quantities determine how many
  machines will be required. Production volume is
  also a factor in selecting the most appropriate
  type of material handling equipment for the
  system.

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FMS Planning and Design Issues(continued)

• Variations in process routings. If variations in
  process sequence are minimal, then an in-line
  flow is most appropriate. As product variety
  increases, a loop is more suitable. If there is
  significant variation in the processing, a ladder
  layout or open field layout are most appropriate.
• Work-in-process and storage capacity. If WIP is
  too low, then stations may become starved. If
  WIP is too high, then congestion may result. The
  WIP level should be planned.

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FMS Planning and Design Issues(continued)

• Pallet fixtures. The number of pallet fixtures
  required in the system must be decided. Factors
  include levels of WIP allowed in the system, and
  differences in part style and size. Parts that
  differ too much require different fixturing.
  Consider modular fixturing.
• Tooling. Tooling decisions include types and
  numbers of tooling at each station.
  Consideration should also be given to the degree
  of duplication of tooling at the different
  stations. Tool duplication tends to increase
  routing flexibility.

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FMS Operational Issues

• Scheduling and dispatching.
• Scheduling of production dictated by the
  master production schedule. Dispatching
  launching of parts into the system at the
  appropriate times.
• Machine loading.
• Allocating operations and tooling resources
  among the machines in the system to accomplish
  the required schedule.
• Part routing.
• Selecting routes to be followed by each part
  in the production mix so as to maximize use of
  workstation resources.

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FMS Operational Issues

• Part grouping.
• Selecting groups of part types for
  simultaneous production, given limitations on
  available tooling and other station resources.
• Tool management.
• Managing available tools includes decisions on
  when to change tools, allocation of tools to
  stations, and similar issues.
• Pallet and fixture allocation.
• Allocation of pallets and fixtures to parts in
  the system.

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Quality Programs SPC, TQM, 6?, etc.

• Presenter Mikell P. Groover
• MSE 438

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SPC, TQM, and 6?

• SPC Statistical Process Control
• TQM Total Quality Management
• 6? Six Sigma
• Other terms associated with quality
• QC Quality Control (Traditional)
• QA Quality Assurance
• QE Quality Engineering (Taguchi)

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Traditional Quality Control

• Focus on inspection detecting poor quality and
  taking corrective action to eliminate it
• Attention on sampling and statistical methods
• Principal tools in statistical quality control
• Control charts
• Acceptance sampling

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Quality Assurance

• Broader scope of activities than quality control
• Not just the inspection department
• Attempts to ensure that a product or service will
  satisfy (or surpass) the requirements of the
  customer

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Total Quality Management

• A management approach that pursues three main
  objectives
• Achieving customer satisfaction
• Internal and external customers
• Importance of product design
• Continuous improvement
• Encouraging involvement of the entire workforce

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Quality Engineering (Taguchi)

• Broad range of engineering and operational
  activities whose aim is to ensure that a
  products quality characteristics are at their
  nominal or target values
• Robust design
• Taguchi loss function
• QE overlaps with TQM

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Robust Design

• A product or process design in which the function
  and performance is relatively insensitive to
  variations (noise factors)
• Unit-to-unit variations - inherent random
  variations in materials, machinery, etc.
• Internal variations wear, fatigues of metals
  parts, operational errors, etc.
• External variations outside temperature,
  humidity, input voltage

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Examples of Robust Design

• Product
• A car that starts in Minneapolis in January as
  well as in Tucson in July
• A tennis racket that returns the ball as well
  when hit near the rim as when hit in dead center
• Process
• A metal forging operation that presses good parts
  despite variations in temperature of the starting
  billet

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Taguchi Loss Function

• A loss occurs when a products functional
  characteristics differ from their nominal or
  target values
• The loss increases at an accelerating rate as the
  deviation grows, according to Taguchi
• Loss function expressed mathematically
• L(x) k(x N)2

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Statistical Process Control

• Involves the use of various methods to measure
  and analyze a process
• Applicable in both manufacturing and service
  operations
• Objectives
• Improve quality of process output
• Reduce process variability and achieve process
  stability
• Solve processing problems

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Seven Tools in SPC

• Control charts
• Histograms
• Pareto charts
• Check sheets
• Defect concentration diagrams
• Scatter diagrams
• Cause and effect diagrams

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Elements of Successful SPC

• Management commitment and leadership
• Team approach to problem solving
• SPC training for all employees
• Emphasis on continuous improvement
• A recognition and communication system

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Six Sigma

• Quality management approach to improve
  effectiveness and efficiency of processes
• Team approach to improvement projects
• Goals of Six Sigma
• Reduce defects
• Reduce variance
• Improve process capability
• Support continuous improvement

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Short History of Six Sigma

• Started at Motorola in mid-1980s
• Mikel Harrys study of process variation
• Supported by CEO Robert Galvin
• Launched at Allied Signal in early 1990s
• Launched at General Electric in 1995
• Jack Welch called it the most challenging and
  potentially rewarding initiative we have ever
  undertaken at GE

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What is a Sigma?

• Sigma (?) refers to the standard deviation of a
  probability distribution
• It is a measure of the variation or spread about
  the mean of the distribution
• Usually refers to a Normal distribution
  (bell-shaped)

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Sigma Value and Defect Rate

• Process sigma Defect rate Yield
• 1? 691,462 pm 30.9
• 2? 308,538 pm 69.1
• 3? 66,807 pm 93.3
• 4? 6,210 pm 99.4
• 5? 233 pm 99.98
• 6? 3.4 pm 99.99966

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Approach in Six Sigma

• Managements responsibility
• Identify key processes in the organization
• Measure the effectiveness and efficiency of these
  processes
• Initiate improvement in the worst performing
  processes

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Some Definitions

• Process a series of steps or activities that
  take inputs, add value, and produce an output
• Effectiveness measure of how well customer
  requirements are met or exceeded
• Efficiency measure of how well resources are
  utilized to achieve effectiveness

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Five Steps in Six Sigma

• DMAIC
• Define the problem
• Measure the process
• Analyze the process
• Improve the process
• Control implement control over the new or
  improved process

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1. Define

• Charter
• Business case why the project should be
  accomplished
• Problem statement
• Goals and objectives
• Milestones measures of progress
• Roles and responsibilities of team members

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Define (continued)

• Identify customer needs and requirements
• Customer recipient of product or service of the
  process to be improved
• Create high-level process map
• Process map flow graph showing the steps and
  decision points in the process

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2. Measure

• Creation of the Data Collection Plan
• Where measurement should occur
• Input measures (supplier effectiveness)
• Process measures (your efficiency)
• Output measures (your effectiveness)
• Types of data
• Discrete data binary (on/off), counts
• Continuous data quantitative over time

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Measure (continued)

• Implementation of the data collection plan
• Collect the data
• Determine baseline sigma of current process
• Calculate defects per million
• Find corresponding sigma level

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Example Food delivery

• Possible defects (1) not on time, (2) order
  incorrect, (3) not fresh
• In 50 deliveries, 13 were not in time, 3 were
  incorrect, and none were not fresh
• DPM D/NC x 1,000,000
• DPM defects per million, D defects (13 3
  0), N no. of units (50 deliveries), C no. of
  defect categories (3)
• DPM 16(50x3) x 1,000,000 106,667
• Current sigma level about 2.75