Describes DFMA with its brief history, steps, advantages and disadvantages This also gives its application through case study of COST REDUCTION OF A DIESEL ENGINE

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Assignment No. 3
on
‘Design For Manufacturing and Assembly (DFMA)’
Submitted by
DESHPANDE ADITYA NARESH
Roll No: S-42, GR No: 142130
(Fourth year B. Tech)
Under the Guidance of
Prof. M. R. Khodke Sir
Department of Mechanical Engineering
Vishwakarma Institute of Technology,Pune
Pune-411037
October 2016

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Introduction: What is “DFMA”?
The concept of DFM (Design for Manufacture) is not new, it dates back as early as 1788 when
LeBlanc, a Frenchman, devised the concept of inter-changeable parts in the manufacture of
muskets which previously were individually handmade. DFM is the practice of designing products
keeping manufacturing in mind. “Design for manufacture” means the design for ease of
manufacture for the collection of parts that will form the product after assembly. Similarly DFA
is called Design for Assembly. DFA is the practice of designing product with assembly in mind.
“Design for assembly” means the design of the product for ease of assembly. So design for
Manufacture and assembly is the combination of DFM and DFA.
Figure No: 1 DFM + DFA = DFMA
History of DFMA:
The following points shows that DFMA has a long history.
Henry Ford an American industrialist was renowned for his advanced and extensive use of
assembly lines. The manual assembly operation was broken down into small chunks of
repetitive work that could be carried out at high efficiency. Ford in his book “My Life and
Work” described about the successful model T car that includes simplicity in operation,
absolute reliability and high quality in materials that used in that model. The concept used
at that time by Ford is now referred as DFM.
General Electric used value analysis techniques in the late 1940s. With the help of value
analysis techniques, it is possible to find the cost of a product and obtaining the design
alternatives for the product at the lowest cost. The philosophical approach of value analysis
is through questioning and comparing the value and cost of each features and each element
of a product design.

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In the recent years various trade association and vendors of parts are issuing booklets to
the product designers providing a series of guidelines and tolerance and materials.
Eli Whitney is an inventor from America used some DFMA techniques in earlier times before
the term DFMA came in to existence. Whitney incorporated the concept of interchangeable
parts for manufacturing musket for U.S. government. Prior to this innovation, each craftsman
was responsible to manufacture the complete product by using saw and files to shape each part
and fit them together.
Steps for applying DFMA during product design:
Figure No:2: Common steps taken in a DFMA study
The following steps are followed when DFMA used in the design process.
 DFMA analysis lading to simplification of the product structure 
 Early cost estimation of parts for both original design and modified design 
 Selecting best material and process to be used 

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 After final selection of material and process carry out a thorough analysis of DFM. Figure 2
depicts the flow diagram of various steps undertaken in a DFMA study using DFMA software.

Advantages of applying DFMA during product Design:
Today products are
 Tending to becoming more complex
 Made/required in increasingly large number
 Intended to satisfy a wide variation in user population
 Required to compete aggressively with similar products
 Required to consistently high quality
Through DFMA it is possible to produce competitively priced, high performance product at a
minimal cost. The advantages of applying DFMA during product design are as follows:
 DFMA not only reduces the manufacturing cost of the product but it helps to reduce the
time to market and quality of the product.
 DFMA provides a systematic procedure for analyzing a proposed design from the point of
view of assembly and manufacture.
 Any reduction in the number of parts reduces the cost as well as the inventory.
 DFMA tools encouraged the dialogue between the designer and manufacturing engineer
during the early stages of design.
Limitation of DFMA:
 Low assembly cost: Since assembly cost of a particular product is less as compared to the total
material and manufacturing cost, DFMA analysis is not required.
 Low volume: Often it is expressed that DFMA is applicable for large quantity production.
 Database doesn't apply to our product: Since DFMA is applied at the early stages of design
before the detail design has taken place; there is a need for a generalized database.

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CASE STUDY: COST REDUCTION OF A DIESEL ENGINE
This work presents a study of manufacture and assembly costs reduction in a diesel engine model
that intends to make this engine economically feasible. The study presents a brief literature review
about product development and technological resources to support product design, emphasizing a
review about the DFMA (Design for Manufacturing and Assembly) method. This presents a
detailed description of how delimited the most critical subsystem of the engine considering the
cost and the application of DFMA guidelines for the delimited subsystem.
Introduction to Diesel engine or engine for ignition by compression is an engine that gets the
ignition without an exterior intervention. The fuel ignition is gotten through the energy resulting
from the compression phase. The increase of the temperature and pressure during the compression
phase is enough to generate the fuel spontaneous ignition.
The main components of a diesel engine are:
1. cylinder block
2. injection pump
3. cylinders
4. cylinder head
5. oil carter
6. piston
7. connecting rod
8. crank shaft
9. flywheel
10. valves
11. camshaft
After the analysis of the engine design, it was identified that the production time is approximately
5 hours and 35 minutes, and the production capacity correspond to one engine in each 7 minutes.
Firstly, the design efficiency is calculated through the following formula: EP = 3 x NP / TM, being
(EP: design efficiency, NP: parts number, and TM: assembly time), detailed in Table 1.
Aiming to suggest the modifications, the study is developed based on the DFMA guidelines that
are as follows:
 To develop modulate designs;
 To design multifunctional components;
 To design components of easy manufacture;

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 To prevent or to reduce setting components (screws,
rivets, bolts);
 To eliminate unnecessary adjusts and tolerances;
 To emphasize the standardization of components;
 To reduce the product parts number;
 To facilitate the manipulation and the assembly of the
final parts; and
 To simplify the product structure, reducing the
assembly costs and other factors of this nature.
METHODOLOGY:
Following the assembly process with the part supplier, it
was possible to observe that these milling and non-pass bores are
unnecessary for the assembly continuity. After all, they do not have direct contact with any part of
the system and do not serve as reference to any other mounted part. After the Oil carter assembly,
this part remains isolated It was detected that the reason of the bores existence was due to the
utilization of the cylinder block design from another engine series that used these bores to fix the
oil fisherman. In the engine X, the oil fisherman is fixed in the balancing set, which is fixed in the
block, becoming the three bores superfluous. Due to this alteration, the cost reduction occurs as
consequence of the economy of machine time, tool consuming, and inspection time of the three
bores. Quantifying this reduction, it implies in 0.05% in the cylinder block cost and 0.03% in the
cost of “Structural and sealing” subsystem.
Another analysis result was to eliminate the block painting. Part of the cylinder block
manufacture process is the electrostatic painting after the casting process. The objective of the
painting is to protect the cylinder block against the corrosion during the transport from the supplier
to the enterprise. Before packing the lot produced by the supplier, the cylinder block receives an
anticorrosive oil application. After that, they are wrapped in plastic films with corrosion inhibitors.
With the block nationalization, the transport time was reduced for two days, making this level of
protection unnecessary. Moreover, it was evidenced that during the engine assembly in the tractor,
the engine and chassis set were entirely painted black, covering any previous painting of the
engine, which made the painting of the cylinder block to become redundant.
Figure no:3 Engine Assembly of
case study

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With this modification a cost reduction occurs in 0.26% in the cylinder block and 0.13%
in the cost of “Structural and sealing” subsystem. Another modification proposal was to eliminate
the puncture and spot facing of the seat of speed sensor. The passing puncture of nominal
diameter 17.1 mm, the M6 thread, and the spot facing shown in Figure 4 are necessary only in the
models with injection through electronic fuel bomb. The engine studied present a mechanical
injection system, making this feature unnecessary. This modification results in a cost reduction of
0.18% in the cylinder block and 0.10% in the cost of “Structural and sealing” subsystem. Following
with the analysis, another modification proposed was to eliminate the identification plate with
the engine serial number, used to register the product.
Table 1. Cylinder block design efficiency calculated before the DFMA study
Now with use of above information following table is constructed which shows use of
DFMA on time and number of parts.

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Table 2. Cylinder block design efficiency calculated after the DFMA study

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Table 3: Features analysed, its costs, the improvements proposed, and cost reductions

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CONCLUSION:
The results show an impact in the cost reduction of the subsystem chosen of 1.8% and in
the entire engine of 0.7% using DFMA (Design for Manufacturing and Assembly) method. For
the application of DFMA method, the study showed the most critical subsystem identification
based on the cost impact in the entire engine and, of this subsystem, the delimitation of the most
representative components.
Potential improvements, they are the following: to reduce tolerances of the casting block,
to remove the guides and seat of valves that are pressed and to substitute them for machining and
posterior thermal treatment, and to reduce finishing specifications in surfaces where silica could
be applied.
REFERENCES
1) Assembly Automation and Product Design G. Boothroyd, Marcell Dekker, Inc.1992
2) Product Design for Manufacture and Assembly G. Boothroyd and P. Dewhurst, Boothroyd
Dewhurst, Inc. 1989 Marcell Dekker, Inc. 1994
3) Design and Analysis of Manufacturing Systems Prof. Rajan Suri University of Wisconsin
1995
4) Product Design for Assembly: The Methodology Applied G. Lewis and H. Connelly
5) Simultaneous Engineering Study of Phase II Injector Assembly line Giddings & Lewis
1997
6) Design for Manufacturing Society of Manufacturing Engineers, (VIDEO)
7) www.dfma.com
8) NPTEL: Design for manufacturing and assembly
lectureshttp://nptel.ac.in/downloads/112101005/