Process Planning

1
Process Planning

• Principle activity of manufacturing engineering
• includes
• Deciding which process and methods to be used in
  what sequence
• Determining tooling requirements
• Selecting production equipment and systems
• Estimating cost of production of selected
  process, tooling, and equipment

2
Computer Aided Process Planning (CAPP)

• CAPP is an automated process planning, can
• be divided into two main sytems
• Retrievel Systems
• Generative Systems

3
Retrieval CAPP systems

• Based on group technology (GT) and part
• classification and coding a standard process plan
  is
• stored in computer files for each part code
  number.
• GT Similar parts identified and grouped together
  in order to take advantage of their similarities
  in design and production.

4
Generative CAPP systems

• Alternative to Retrieval systems. Rather than
  retrieving and editing an existing plans from a
  data base, a generative system creates the
  process plan using systematic procedures that
  might be applied by a human planner.
• In fully Generative CAPP system, a process
  sequence is planned without human assistance and
  predefined parts.
• It is a branch of artificial inteligence
  Expert Systems. Computer Programs are capable
  of solving complex problems that normally
  requires a human.

5
Generative CAPP systems (continue)

• Several ingredients needed
• Knowledge Base Technical knowledge of
  manufacturing and the logic used by a succesfull
  process planners must be captured and coded into
  a computer program. Generative CAPP systems use
  the knowledge base to solve the process planning
  problems and to create route sheets.
• Computer Compatible Part Description Description
  contains all the data needed to plan the process
  sequence. For example
• Geometric model of the part developed on a CAD
  system

6
Generative CAPP systems

• Group technology code number of part defining its
  significant features is given.
• Inference Engine A generative CAPP system
  requires the capability to apply the planning
  logic and process knowledge contained in the
  knowledge base to a given part description. CAPP
  applies its knowledge base to solve a specific
  problem of planning the process for a new part.
  This procedure is called Inference Engine

7
Benefits of CAPP systems

• Process rationalization and standardization
  (logical and consistent)
• Increased productivity (greater number of process
  plans to be developed)
• Reduced lead time
• Improved legibility
• Interfacing with other programs (cost estimation,
  etc..)

8
Concurrent Engineering

• Companies attempt to reduce the elapsed time
• required to bring a new product to market by
• integrating design engineering, manufacturing
• engineering and other functions in the company.
• Traditional approach is to seperate design and
• manufacturing. There is only a little interaction
  
• between these two groups.
• In a company that practices concurrent
• engineering, manufacturing planning starts while
  the
• product design being developed. Consists of DFM/A
• and DFQ, design for life cycle and cost.

9
Design for Manufacturing and Assembly (DFM/A)

• To implement DFM/A, a company must
• make changes in its organizaitonal structure
• and design principles and guidelines.
• Organizational changes need to be done to have
  better intraction between design and
  manufacturing personnel.
• Organizational changes must contain
• a)Team formed of designer, manufacturing
  engineers, quality engineers, material engineers,
  etc.

10
Design for Manufacturing and Assembly (DFM/A)

• b)Designers must spend some time in
  manufacturing area.
• c)A manufacturing engineer should consult the
  designers.
• 2) One of the guide lines in designing is to make
  it as simple as possible, but in design for
  assembly, additional features are required, such
  as to be technically good in manufacturing, is
  it safe from copying( can competitors learn the
  secrets of our product by reverse engineering?).

11
Benefits of DFM/A

• Shorter time to bring product to the market
• Smoother transition into production
• Fewer components in final product
• Easier assembly
• Lower cost of production
• Higher product quality
• Greater customer satisfaction

12
Design for Quality (DFQ)

• Traditional quality control has been concerned
• with detecting the oor quality in manufactured
• products and taking corrective action to
• eliminate it.
• The modern view of quality control
• encompasses a broader scope of activities
• including robust design and statistical process
• control.

13
Design for Quality (DFQ)(continue)

• Robust Design Products function and
• performance is not sensitive to the variations in
• design and manufacturing parameters. It
• involves the design of both the product and
• process.
• Statistical Process Control(SPC) Involving the
• use of statistical methods to assess and analyze
• the variations in process. This method includes
• keeping records of production data and charts.

14
Design for Life Cycle

• Factors associated with life cycle
• 1)DeliveryTransport cost, delivery time, etc..
• 2)InstallabilityUtility requirements.
• 3)ReliabilityService life,failure rates, etc..
• 4)MaintainabilityDesign modularity,maintenance
• requirements.
• 5)ServiceabilitySpare parts, field service.
• 6)Human factorsComplexity of controls,risks,
  etc..
• 7)UpgradeabilityCompatibility to the future
  designs.
• 8)DisposabilityRecycling of components, waste
• hazards, etc..

15
Design for Cost

• In manufacturing our main aim is to reduce the
  cost of
• production. Of course we need to make the
  processes
• easy and quality high. Choosing the best material
  and
• manufacturing processes among all the available
• materials and processes is a complex decision
  making.
• In cost reducing there is two main factors
• Role of materials
• Role of manufacturing processes

16
Role of Materials

• Understand the functional requirements of each
  part,
• choosing criteria will include
• Mechanical properties of the material Strength,
  toughness, ductility, hardness, etc..
• Physical properties of the material Density,
  melting point, thermal expansion, etc..
• Chemical properties of the material Oxidation,
  corrosion, etc..
• Shape of the materialNeed to select the shape
  with respect to the design, therefore it requires
  less additional process.

17
Role of Materials (continue)

• Manufacturing properties of the material Need to
  select the suitable material for the process that
  is going to be applied.
• Material supply Location of the plant, location
  of the country, politics in the country affects
  the availabitiy of the material. Therefore the
  cost.
• Material cost Cost of a raw materialdepends not
  only on the material itself but also on its
  shape, size and condition. Also, price of a
  material decreases as the volume increases.Demand
  is another aspect in the price of a material.

18
Role of Materials (continue)

• Product design Cost of material is a significant
  portion of product cost. This cost can be reduced
  by optimization in design or reducing thickness.
  But minimization in material thickness may cause
  problems in manufacturing.
• Substitution of materials New products appear
  continually in the market to substitude the
  materials in use. The purpose of substitution is
  to reduce the cost of the material, to improve
  manufacturing and assembly, to reduce
  maintenance, etc...

19
Role of Manufacturing Processes

• Proper selection of manufacturing processes and
• machinery depends on various considerations like
• Properties of the work material
• The shape and the size of the work material
• Surface finish and dimensional tolerances
• Quantity of the production
• Functional requirements
• Process capabilities

20
Manufacturing Cost

• Material cost
• Tooling cost
• Fixed costs
• Capital costs
• Direct labor costs
• Indirect labor costs
• We talked about the material and tooling
  previously.

21
Manufacturing Cost (continue)

• Fixed costsElectric, fuel, taxes, rent,
  insurance type of costs called fixed costs. These
  costs are not sensitive to the production volume.
• Capital costsInvestment in land, building,
  machinery,tooling and equipment.
• Direct labor costsIncludes all labor, from the
  time raw materials are first handled to the time
  when the product is finisihed. This period is
  called as floor-to-floor time, and the personnel
  is called productive labor.
• Indirect labor costsThese costs are refered to
  as overhead (burden rate) and charged
  proportionally to all products. The personnel
  involved in activities such as quality control,
  repair, maintenance, engineering, research,
  sales, etc called non-productive labor creates
  these costs.

22
Manufacturing Cost and Production Rate

• Approximate cost division
• Design 5
• Material 50
• Direct labor 15
• Overhead 30
• Ofcourse the direct labor costs changes with
  respect to the
• manufacturing volume. High volume type of
  manufacturing
• includes dedicated machinery which needs less
  direct labor.
• On the other hand small volume productions needs
  more direct
• Labor since the machinery used is general purpose
  type of
• Machines and needs more human interaction.

23
Cost Reduction

• Cost can be reduced by
• Simplifying part design
• Allowing rougher surface finish and broader
  tolerancing
• Using less expensive material
• Investigating the alternative ways of
  manufacturing
• Using efficent machinery
• Since manufacturing adds value to materials by
  using value analysis methods we can reduce the
  cost.

24
Value Analysis

• Value analysis consists of six phases
• Information phase gather data and determine cost
• Analysis phaseIdentify problems and
  opportunities
• Creativity phaseSeek ideas to solve problems
• Evaluation phase Select ideas and identify costs
  involved.
• Implementation phaseTake necessary actions to
  accomplish the task
• Review phase Analyze to see if any adjustment is
  needed