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The 3D
product-model is the connecting link between the various
computer-aided programs (referred later as CAX-where 'X' could
mean design, engineering, manufacturing, or inspection). The
programs generate a huge amount of data, which includes the solid
models of different iterations and previous versions of products,
as well as tooling, materials, process plans, and results of
analysis. This necessitates a systematic approach to data storage,
verification, and retrieval–achieved by a product data management
(PDM) system.
The PDM
systems have rapidly evolved over the last decade, and now allow
distributed storage and remote access over Internet. They provide
better data translation for exchange among various teams. Security
is handled by data encryption during exchange, and by facilities
for setting limits of access by non-core team members. Also, some
useful utilities may be provided for collaboration. For example,
comments or suggestions can be attached to product features.
Additionally, two or more team members can synchronise their
computer displays, point out product features (by an arrow visible
to all team members), and discuss improvements using a messaging,
or videoconferencing facility.
A complete set of computer-aided programs, PDM system, and
collaboration utilities, is now referred to as a-product lifecycle
management (PLM) solution. The set may be offered entirely by a
single vendor (such as Dassault Systems, France; Electronic Data
Systems, USA; or Parametric Technology Corp, USA) or can be put
together by integrating the most suitable program for each
application (e.g. SolidWorks for CAD, ANSYS for CAE, Delcam for
mould design and CAM, MoldFlow for plastic flow simulation and
MatrixOne for PDM).
Designing Beyond Functionality
A well-designed product not only satisfies its functional
requirements, but also is easier to manufacture, maintain,
deliver, and dispose off. Often, even minor modifications to an
existing design (such as changing a fillet radius or shifting a
boss) may yield significant reduction in costs, defects or
lead-time. Such changes are easy and inexpensive for a new product
during its design phase. The same changes during manufacturing
phase would entail redoing the tooling and process planning, which
is several times more expensive and time-consuming. The costs
mount further if the products have already been delivered to
customers and have to be recalled to fix a problem that could have
been foreseen and prevented by a better design in the first place.
Design for Manufacture (DFM) is influenced by product geometry,
material, and process. For example, injection moulded plastic
parts need to be designed with a uniform wall thickness to
minimise the production cycle time, and avoid sink marks; metal
castings must be designed for directional solidification for ease
of feeding; forged parts must have generous radii of curvature to
facilitate flow of metal; and sheet metal parts made by blanking
operations, must be designed for efficient nesting and thereby,
stock utilisation.
Similar guidelines are also available for improving a product
design for ease of assembly, service, transportation and
environment. Design for Assembly (DFA) guidelines include
reduction of number of parts, and number of assembly directions.
Design for Service guidelines include modular design, and ease of
access. Design for Transportation guidelines include provision of
suitable hooks and handles for lifting the part. Design for
Environment (DFE) guidelines include use of recyclable materials
(metals are better than plastics), reduced packaging, and
improving the energy efficiency of the product. The guidelines
(referred later as DFX–where X could mean manufacture, assembly,
service, transportation, or environment) are distilled from
practical experience on previous products, and may not be
applicable to new materials or processes. They may also conflict
with each other, but provide no quantitative feedback to resolve
such conflicts. Moreover, most designers have little time,
interest or knowledge in handling product lifecycle issues beyond
functionality. One way to overcome these problems is to invite
external experts to evaluate the design for various design
considerations and suggest suitable improvements. Since the
experts are likely to be inaccessible (in terms of time or
distance), a web-based PLM system greatly facilitates such
collaborations......more on next page
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Editorial