Manufacturing system design

1. 15MF110-MANUFACTURING SYSTEMS
DESIGN
UNIT-I
INTRODUCTION TO MANUFACTURING
SYSTEMS ENGINEERING
Done by
S. Annamalai
S. Ayyandurai
A. Karthik
M.E. Manufacturing Engineering20-12-2018 1

2. Introduction to Manufacturing Systems Engineering
Process Planning – Logical design of a process planning – Shortcomings
of traditional process planning – Computer aided process planning –
Computerization of files management – Variant (Retrieval) approach –
generative approach – Semi generative approach – General remarks on
CAPP developments and trends.
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3. Manufacturing Systems
We define a manufacturing system to be a collection of
integrated equipment and human resources, whose function
is to perform one or more processing and/or assembly
operations on a starting raw material, part, or set of parts.
The integrated equipment includes production machines
and tools, material handling and work positioning devices,
and computer systems.
Human resources are required either full time or
periodically to keep the system running.
The manufacturing system is where the value-added work is
accomplished on the part or product.
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4. Manufacturing Systems
Manufacturing
Systems
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5. Components of a Manufacturing System
A manufacturing system consists of several components. In a
given system, these components usually include:
• Production machines plus tools, fixtures, and other related
hardware
• Material handling system
• Computer systems to coordinate and/or control the above
components
• Human workers
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6. 1.1 Process Planning
The activity that translates part design specifications
from an engineering drawing into the manufacturing
operation instructions required to convert a part from a rough
to a finished state.
It represents the link between engineering design and
shop-floor manufacturing. It is a major determinant of
manufacturing cost and profitability. The gap between CAD
and CAM can be shortened considerably by developing better
systems for process planning.
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7. Scope of process planning
• Interpretation of design drawings. The part or product design must be
analysed (materials, dimensions, tolerances, surface finishes, etc.) at
the start of the process planning procedure.
• Processes and sequence. The process planner must select which
processes are required and their sequence. A brief description of all
processing steps must be prepared.
• Equipment selection. In general, process planners must develop plans
that utilize existing equipment in the plant. Otherwise, the
component must be purchased, or an investment must be made in
new equipment.
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8. • Tools, dies, molds, flxtures, and gages. The process planner must decide
what tooling is required for each processing step. The actual design and
fabrication of these tools is usually delegated to a tool design department
and tool room, or an outside vendor specializing in that type of tool is
contracted
• Methods analysis. Workplace layout, smaf tools, hoists for lifting heavy
parts, even in some cases hand and body motions must be specified for
manual operations. The industrial engineering department is usually
responsible for this area.
• Work standards. Work measurement techniques are used to set time
standards for each operation.
• Cutting tools and cutting conditions. These must be specified for machining
operations, often with reference to standard handbook recommendations.
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9. Process planning for parts
For individual parts, the processing sequence is documented on
a form called a Route sheet. (Not all companies use the name route
sheet; another name is "operation sheet.")
Just as Engineering drawings are used to specify the product
design, route sheets are used to specify the process plan.
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10. Route sheet
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11. Process sequence
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12. Typical process sequences
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13. 1.2 Logical design of a process plan
1. Preliminary analysis of a design inpyt
2. Material selection
3. Process sequence
4. Machine and tool selection
5. Fixture selection
6. Machining parameter selection
7. Cost/time estimation
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14. To give a global idea of the preparation of a process plan, it
seems appropriate to analyse a typical mechanical part and to define
the different stages of decisions to be taken. It is clear that many of the
logical steps taken in machining can be transferred easily to other
processes.
Having correctly analysed the part drawing from a geometric
point of view, it should be possible to define the process plan on the
basis of information available on production facilities(machine, tooling,
accuracy capabilities etc.,)
Before going into detail, study the outline of the part inorder to
think of ways of designing its final process plan.
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15. 1.3 Shortcomings of Traditional Process Planning
The approach becomes rapidly inefficient and
unmanageable when the number of process plans and
revision to those plans increase. Consequently,
inconsistent plans and large time requirements for
planning often result.
The plans by this approach reflect the personal
experiences and preferences of the process planner.
This is considered a poor use of engineering skills
because of the high clerical content in most of its
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16. Approaches in Process Planning
Process
planning
Computer
Aided Process
Planning
Variant
Approach
Generative
Approach
Semi-
Generative
Approach
Manual
Process
Planning
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17. Manual Process Planning
Traditionally, skilled planners perform process planning.
Planning is based on planner’s decisions.
The quality of the plan highly depends on individual skill,
knowledge and experience.
Planning is very time consuming, because of voluminous
routine work and calculations.
Only little time is left for creative work and updating
planner’s knowledge.
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18. 20-12-2018 18

19. Importance of Computer Aided Process Planning
 The aim of Computer Aided Process Planning is to eliminate or at least
reduce the manual intervention in process planning.
 By using a computer, the tedious and repetitive aspects of process planning
can be speeded up and this helps to optimise the total manufacturing
function by releasing the experienced planners and enabling them to
concentrate on those aspects outside the scope of a computer.
 At the same time, more consistent process plans can be obtained by
applying a standard set of rules, which increases confidence in the system
and helps in the rationalisation of production.
 To automate process planning, the logic, judgement and experience
required for process planning must be captured and incorporated into a
computer program.
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20. 20-12-2018 20

21. Conventional Vs CAPP
The advantage of CAPP over conventional process planning is manifold.
 It improves the quality and consistency of process plans.
Savings in lead time: In today’s concepts of TQM and batch manufacturing
lead time seriously effects the delivery time of the product which plays a
major role in deciding the market share of any company.
 Process rationalisation: CAPP generated process plan is more likely to be
consistent (because the use of same software for all plants), logical and
optimal (because the company has presumably incorporated the
experience and judgement of its best manufacturing people into process
planning software and computer can evaluate more number of alternatives
in a less time).
 Integration with manufacturing support functions: These functions involve
NC part program generation, computerised work standards etc., If done
independently these functions involve duplication of clerical work.
Increases the efficiency of process planning.
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22. The advantage of CAPP over conventional process
planning is manifold.
Decreases the variety of tooling.
Error reduction: Helps in overcoming the casual errors
committed by human process planners. If the error goes
unnoticed, it penalise heavily from the cost point of view.
It can reduce the skill required by planners.
It can increase productivity.
It can consider all available equipment while process
planning.
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23. Objectives of Process Planning Systems
Consistency
A good process planning system should provide
consistently same process plan for same set of input data.
Accuracy
Accuracy is another important objective to maintain in
any process planning system.
Inaccuracies in process plans and corresponding
information in them can greatly undermine the integrity of the
system.
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24. Ease of application
This is another important trait, which determines how quickly a
response can be made to generate a new process plan or make revision
to an existing process plan.
This is of particular importance in today's short lead-time
environment
Completeness
Information about manufacturing processes, machines, tools,
cutting parameters etc., must be completely known while decisions
about process planning g are made.
If complete data is not provided, then the choice can easily lead
to inconsistency in processing methods and corresponding
inconsistencies in part quality and costs.
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25. Challenges in the area of CAPP
Process planning systems, in order to provide integration, automation and
flexibility should
■ be generative
■ be technology based
■ use features as a technological and communicational interface between design
and process planning
■ be able to extract automatically all product data
■ use a supervisory control system to ensure user-friendliness and flexibility in
use
■ integrally support all planning tasks, including capacity planning and scheduling
■ take decisions based on optimization techniques
■ be fit for close-loop planning20-12-2018 25

26. 1.4 COMPUTER AIDED PROCESS PLANNING

44. 1.5 Computerization of files management
• This is the first step in computer aided process planning
• A computer is a machine built to store and retrieve data at high speed; it
performs computations at high speed and with accuracy;
• The current idea is to utilize the power of computers to assist the process
planner with clerical work, leaving him/her free for technical work.
• The idea is to divide the work between the process planner and the
computer, letting each perform the tasks they know best.
• This will reduce the pre-production lead times and increase process
planner productivity by 600%, allowing more time to be spent on the
planner evaluating alternatives. The result will be complete and consistent
processes.
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45. Approaches to CAPP
• Variant Approach
• Generative Approach
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46. 1.6 Variant Approach
The variant approach is comparable with the traditional
manual approach where a process plan for a new part is
created by recalling, identifying, and retrieving an existing
process plan for similar part, and making necessary
modification making it suitable for the new part.
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47. Variant Approach
In general this system has two operational stages.
i. Preparatory stage: in this stage the parts are coded and
families are formed based on group technology (GT)
principles. Standard process plans are prepared for each
family and stored in database.
ii. Production stage: Process plan for a new part can be
made in this stage. Whenever a new part comes for process
planning, it’s code and family will be identified and the
standard processing plan for that family is retrieved.
Necessary modifications are made by the process planner to
satisfy the component design.
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49. 1.7 Generative Approach
Generative CAPP systems represent an alternative approach to
automated process planning.
Instead of retrieving and editing an existing plan contained in a
computer data base, a generative system creates the process plan
based on logical procedures similar to the procedures a human planner
would use.
In a fully generative CAPP system, the process sequence is
planned without human assistance and without a set of predefined
standard plans.
The problem of designing a generative CAPP system is usually
considered part of the field of expert systems, a branch of artificial
intelligence.
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50. Generative Approach Contd..,
An expert system is a computer program that is capable of solving
complex problems that normally require a human with years of education
and experience.
There are several ingredients required in a fully generative process
planning system.
First, the technical knowledge of manufacturing and the logic used by
successful process planners must be captured and coded into a computer
program.
In an expert system applied to process planning, the knowledge and
logic of the human process planners is incorporated into a so-called
"knowledge base”. The generative CAPP system then uses that knowledge
base to solve process planning problems {i.e., create route sheets).
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51. 1.8 Semi-generative Approach
This approach is the combination of variant and generative
approaches.
However, compared with the variant systems, editing work is
less.
The advantage of using such systems is reduced time for
preparation of process plans; modifications of generated process
plans are necessary in order to implement in the real work.
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52. 1.9 RECENT TRENDS IN CAPP
In the global competitive market, various areas such as
design process planning, manufacturing and inspection plays a
vital role in reducing cost and lead time.
In the various areas, different kind of interference
mechanism has been developed. A lot of difficulty arises while
integrating the goal in CIM environment.
The major challenges of and research areas are to make
CAPP system affordable to the medium and small scale
manufacturing industries.
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53. Recent trends in CAPP systems include :
•Automated translation of the design dimensions.
•Tolerances into manufacturing dimensions.
• Tolerances considering process capabilities.
•Dimensional chains.
• And to make CAPP system affordable for small and
medium scale manufacturing industries.
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54. THANK YOU
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