Design for Manufacturing

By : Omer Chasib k.

2014

University of BaghdadAl-Khwarizmi College of Engineering

Automated Manufacturing Engineering Department

Purpose Statement

To provide an overview of Design for

Manufacturing and Assembly (DFMA)

techniques, which are used to minimize

product cost through design and process

improvements.

Design for Manufacturing

Definition: DFM is the method of design for ease of manufacturing of the collection of parts that will form the product after assembly.

‘Optimization of the

manufacturing

process…’

DFA is a tool used to select the most cost effective material and

process to be used in the production in the early stages of product

design.

Major DFM objectives

1) Estimate the mfg. costs2) Reduce the costs of components3) Reduce the costs of assembly4) Reduce the costs of supporting production5) Consider the impact of DFM decisions on other

factors.

Design for Assembly

Definition: DFA is the method of design of the product for ease of assembly.

‘…Optimization

of the part/system

assembly’

DFA is a tool used to assist the design teams in the design of

products that will transition to productions at a minimum cost,

focusing on the number of parts, handling and ease of assembly.

Differences

Design for Assembly (DFA)

• concerned only with reducing product assembly cost▫ minimizes number of assembly operations

▫ individual parts tend to be more complex in design

Design for Manufacturing (DFM)

• concerned with reducing overall part production cost▫ minimizes complexity of manufacturing operations

▫ uses common datum features and primary axes

Similarities

• Both DFM and DFA seek to reduce material, overhead, and labor cost.

• They both shorten the product development cycle time.

• Both DFM and DFA seek to utilize standards to reduce cost

Terminology

Design for Manufacturing (DFM) and Design for Assembly (DFA) are now commonly referred to as a single methodology, Design for Manufacturing and Assembly (DFMA) .

Sequence of Analysis

Concept Design

Design for

Assembly

Design for

Manufacturing

Detailed Design

Design for Manufacturing (DFM) and design for assembly (DFA) are the integration of product design and process planning into one common activity.

The goal is to design a product that is easily and economically manufactured.

The heart of any design for manufacturing system is a group of design principles or guidelines that are structured to help the designer reduce the cost and difficulty of manufacturing an item. The following is a listing of these rules

Reduce the total number of parts

The reduction of the number of parts in a product is probably the best opportunity for reducing manufacturing costs. Less parts implies less purchases, inventory, handling, processing time, development time, equipment, engineering time, assembly difficulty, service inspection, testing

Develop a modular design

The use of modules in product design simplifies manufacturing activities such as inspection, testing, assembly, purchasing, redesign, maintenance, service

Use of standard components

Standard components are less expensive than custom-made items. The high availability of these components reduces product lead times.

Design parts to be multi-functional

Multi-functional parts reduce the total number of parts in a design, thus, obtaining the benefits given in rule 1. Some examples are a part to act as both an electric conductor and as a structural member, or as a heat dissipating element and as a structural member.

Design parts for multi-use

In a manufacturing firm, different products can share parts that have been designed for multi-use. These parts can have the same or different functions when used in different products.

In order to do this, it is necessary to identify the parts that are suitable for multi-use. For example, all the parts used in the firm (purchased or made) can be sorted into two groups: the first containing all the parts that are used commonly in all products.

Design for ease of fabrication

Select the optimum combination between the material and fabrication process to minimize the overall manufacturing cost. In general, final operations such as painting, polishing, finish machining, etc. should be avoided. Excessive tolerance, surface-finish requirement, and so on are commonly found problems that result in higher than necessary production cost.

Avoid separate fasteners

The use of fasteners increases the cost of manufacturing a part due to the handling and feeding operations that have to be performed. Besides the high cost of the equipment required for them, these operations are not 100% successful, so they contribute to reducing the overall manufacturing efficiency. In general, fasteners should be avoided and replaced, for example, by using tabs or snap fits.

Fastener Cost

•Select the

most

inexpensive

fastening

method

required

plastic bending

riveting

screwing

snap fit

General Design Principles

Self-fastening features

Minimize assembly directions

All parts should be assembled from one direction. If possible, the best way to add parts is from above, in a vertical direction, parallel to the gravitational direction (downward).

In this way, the effects of gravity help the assembly process, contrary to having to compensate for its effect when other directions are chosen.

General Design Principles

Top-Down Assembly

Handling Difficulty

• Size

• Thickness

• Weight

• Fragility

• Flexibility

• Slipperiness

• Stickiness

Handling Difficulty

size slipperiness

sharpness flexibility

Ensure parts do not need to be held in position

Reference

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