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DESIGN FOR MANUFACTURING (DFM)
Sergio Antonio Salvi
PRODUCT DEVELOPMENT
DESIGN FOR MANUFACTURING
DFM concept
The Design for Manufacturing (DFM, also called “… for manufacturability”; cf. Boothroyd, Dewhurst), is a methodology that extends the recommendations of Design for Assembly (DFA), an engineering design approach developed in the eighties.
DFM and DFA come from the need to “drive cost”: design a product so that it is easily manufactured and assembled, means to save money.
In the field of the so called “design sciences” (born in Europe in the sixties), this innovation has also generated the concept “Design for X” (DFX, cf. Ulrich, Eppinger, 2000), in which the “parameter X” represents the problem that must be solved; in other words, the “main direction” the product development must follow (nowadays, for example, Design for X can be “declined” into “Design for Cost”, “Design for competitiveness” etc.).
PRODUCT DEVELOPMENT
Sergio Antonio Salvi
DESIGN FOR MANUFACTURING
“Input” and “output” flows in a productive system
PRODUCT DEVELOPMENT
Sergio Antonio Salvi
RAW MATERIALSAND SEMIFINISHED
MATERIALS
ENERGY
WASTE
FINISHED ORSEMIFINISHEDPRODUCTS
informaz. services manpower(labour)
toolsexternal
“standardcomponents”
equipments
PRODUCTIVESYSTEM
informat.
MANUFACTURING COST
ASSEMBLINGCOMPONENTS GENERAL COSTS
internal(“already made”)
external(“to buy”)
to design(“to make”)
standard
row materials
process
tools
process
tools
labour
labour
support
indirect allocations
DESIGN FOR MANUFACTURING
product manufacturing cost elements
PRODUCT DEVELOPMENT
Sergio Antonio Salvi
MANUFACTURING COST
ASSEMBLINGCOMPONENTS GENERAL COSTS
internal(“already made”)
external(“to buy”)
to design(“to make”)
standard
row materials
process
tools
process
tools
labour
labour
support
indirect allocations
DESIGN FOR MANUFACTURING
DFM principles
Referring to design development strategies, DFM, as mentioned, happens to be the most important methodology, due to its direct influence over production’s costs. It contemplates the following stages (cf. Ulrich, Eppinger, 2000):
(→□)
■ 1. production cost estimate;
■ 2.1 components cost reduction;
■ 2.2 assembly cost reduction (cf. DFA, design for assembly);
■ 2.3 production support cost reduction;
■ 3. evaluation of DFM decisions impact over other factors;
■ 4. production cost recalculation.
PRODUCT DEVELOPMENT
Sergio Antonio Salvi
DESIGN FOR MANUFACTURING
DFM flows
(→□)
1. production costestimate
briefing
4. production costrecalculation
2.2 assembly costreduction
3. evaluation of DFMdecisions impact
2.1 components costreduction
2.3 productionsupport cost red.
yesproject development
nofair?PRODUCT
DEVELOPMENT
Sergio Antonio Salvi
DESIGN FOR MANUFACTURING
2.1 components cost reduction: ”NETSHAPE” MANUFACTURING
■ “Net-shape” manufacturing (in a completely definitive way) previews the use of construction processes able to a functional integration of the manufacture goods through its production in only one stage.
■ Components reduction, which is determined by the net-shape processes choice, avoids to resort to different technologies and therefore to materials and to unlike parts management, reducing at the same time costs of assembly.
■ Technologies that mostly satisfy this principle are those using moulds, injection moulding and die casting for first.
(→□)
PRODUCT DEVELOPMENT
Sergio Antonio Salvi
DESIGN FOR MANUFACTURING
2.1 components cost reduction: ”NETSHAPE” MANUFACTURING
PRODUCT DEVELOPMENT
Sergio Antonio Salvi
DESIGN FOR MANUFACTURING
2.1 components cost reduction: CHOICE OF THE ECONOMICAL SCALE
■ Usually manufacture cost decreases with the increase of production volume. This happens because the “fixed costs” are divided from the produced units (“amortization”) and, together, “variable costs” decrease due to the fact that the company can justify the access to a bigger scale economy (for example, buy the material at a lower cost).
■ In a productive system fixed costs are represented, for instance, from manufacturing equipment (“set up” operations and, in the most typical case, tools design and construction: cuttings, moulds and so on).
■ Variable costs (variable along with the production!) are instead traceable to: materials, machine-hours and so on.
■ In other words: to produce few units it is convenient to have available processes at low fixed costs and high variable costs; on the contrary for what concerns high productions.
(→□)PRODUCT DEVELOPMENT
Sergio Antonio Salvi
DESIGN FOR MANUFACTURING
2.1 components cost reduction: CHOICE OF THE ECONOMICAL SCALE
produced units
total cost
machine toolmachining
injectionmoulding
mould cost
set up cost
equality point
PRODUCT DEVELOPMENT
Sergio Antonio Salvi
DESIGN FOR MANUFACTURING
2.1 components cost reduction: STANDARDIZING COMPONENTS
■ The use of standard components in the industrially produced object is fundamental. Their use means you don’t have to be in charge of their design (or redesign them) and to produce them (or produce them again). In the historic scenery of productions oriented towards design there are even some objects, called “ready-made”, which were almost integrally built resorting to parts already in the market.
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■ External standard components, parts that can be acquired “through a catalogue”, are produced by specialised suppliers and traded at a restrained cost, justified by their high production. Besides, for the same reason, their quality is medium-high. Examples of this category are the mechanical union elements (screws, and so on) and some electrical devices (engines, cables and so on).
■ Unfortunately, often some parts don’t interest this kind of market, but now and then, a company may decide to design and produce internal standard components, able to satisfy the needs of products frequently based on the same platform (wheel rims in cars, toners cartridges and so on).
DESIGN FOR MANUFACTURING
2.1 components cost reduction: STANDARDIZING COMPONENTS (“Mezzadro” by A. and P. Castiglioni; seat was first applied to an agricultural vehicle)
PRODUCT DEVELOPMENT AND MANUFACTURING TECHNOLOGIES
Sergio Antonio Salvi
DESIGN FOR MANUFACTURING
2.1 components cost reduction: “BLACK BOX” METHOD
■ “Black box” components acquisition method has origin in the Japanese automotive industry experience (cf. Clark, Fujimoto, 1991). It was found out that giving only target specifications to supplier (the product requirements asked for), without an executive project, generated a process of cost reduction and of quality increase.
■ This methodology is obviously sustainable when the interaction with product arquitecture and its components, assembly interface (and so on) are communicated precisely. Consider also the importance of putting in competition a series of suppliers.
■ The advantages are significant: an activity of research and development at zero costs is set up, there is no need for an internal design of parts, as a consequence the company is partially taken off responsibility.
PRODUCT DEVELOPMENT AND MANUFACTURING TECHNOLOGIES
Sergio Antonio Salvi
OMITTED