Introduction:
Definition, need for DFM, DFM approach for cost reduction, general design guide lines of DFM, advantages and disadvantages, application of DFM in industries, Design for Quality Manufacturability, DFQM approach, designing for economical production. Design for Excellence (DFX).
Engineering Tolerancing:
Basics of dimensional tolerancing, Redundancy, tolerance allocation, Review of relationship between attainable tolerance grades and different machining processes. Geometrical tolerances. Process capability, mean, variance, skewness, kurtosis, process capability indices- Cp, and Cpk. Cumulative effect of tolerance- Sure fit law and truncated normal law, problems.
True positional theory:
Comparison between coordinate and true position method of feature location. True position tolerance- virtual size concept, concepts of datum and changing datum, floating and fixed fasteners, projected tolerance zone and functional gages. Concept of Zero true position tolerance. Simple problems on true position tolerancing.
Selective Assembly:
Interchangeable part manufacture and selective assembly. Deciding the number of groups -model-1: group tolerance of mating parts equal, model- 2: total and group tolerances of shaft equal. Control of axial play- introducing secondary machining operations, and laminated shims; examples.
Datum Features:
Functional datum, datum for manufacturing, changing the datum; examples.
Component Design:
Design features to facilitate machining: drills, milling cutters, keyways, Doweling procedures, counter sunk screws, Reduction of machined area, simplification by separation, simplification by amalgamation, Design for machinability, Design for economy, Design for clampability, Design for accessibility. Designing for heat treatment, roller burnishing, and economical de-burring.
Design of components with casting considerations:
Pattern, mould, and parting line. Cored holes and machined holes. Identifying the possible and probable parting lines. Castings requiring special sand cores. Designing to obviate sand cores.
Welding considerations:
Advantages of weldments over other design concepts, design requirements and rules, redesign of components for welding; case studies.
Forging considerations -
requirements and rules-redesign of components for forging and case studies.
Design of components for powder metallurgy-requirements and rules-case studies.
Design of components for injection moulding-requirements and rules-case studies.
Course Outcomes:
At the end of the course, the student will be able to:
CO1: Select proper materials and manufacturing processes for designing products/components by applying the relevant principles for ease and economic production.
CO2: Identify faulty design factors leading to increased costs in producing mechanical components.
CO3: Apply appropriate design tolerances – dimensional, geometric and true position tolerances for the production processes of mechanical components.
CO4: Apply the concepts related to reducing machined areas, simplification by amalgamation and separation, clampability, accessibility etc., in the design of mechanical components.
CO5: Analyse the design of castings, weldments, forgings, powder metallurgy components and suggest design modifications to reduce the cost.
Question paper pattern:
Textbook/s
1 Designing for Manufacture Peck H Pitman Publications 1983
2 Engineering Design: A Materials and processing Approach Dieter, G.E. McGraw Hill Co.Ltd 2000
3 Handbook of Products Design for Manufacturing: A Practical Guide to Low-cost Production Bralla, James G. McGraw Hill, New York 1986
Reference Books
1 Engineering Design Eggert, R.J Pearson Education, Inc., New Jersey 2005
2 Engineering Design Matousek , R Blackie and Son Limited, Glasgow 1967
3 Engineering Design for Manufacture Kalandar Saheb, S.D and Prabhakar, O. ISPE 1999
4 Design for Economical Production Trucks, H.E. Mich., Dearborn, SME 2 nd ed.,1987
5 Processes and Materials of Manufacture Linberg, Roy A. Allyn and Bacon, Boston, U.S.A. 4 th ed., 1990