Concurrent Engineering vs. Serial Engineering
Computer aiaded Concurrent Engineering seamlessly integrates design,
analysis, prototyping and manufacturing stages, greatly reduces the design to
manufacturing time cycle.
Conventional engineering processes, commonly being referred to as Serial
Engineering Processes, follows a linear path, with each step beginning only
after the last is completed (Fig. 1). So the design (Conceptual design
and Detail design) should be performed at first, followed by the Analysis and
Prototype. Any change will result in the repeated work from design stages. After
the design passes the analysis and prototype, it is sent to the shop. If any
further change is required, either in the Manufacturing preparation stage, or
due to a change of purchasing or suppliers, the whole design needs to be passed
back to the very beginning (the design stage). In those processes, engineers and
others are isolated to each other. No matter how efficient the serial approach
becomes, it's still slower and more error-prone than the parallel approach of
Fig. 1: Traditional Serial Engineering Processes 
With a concurrent approach to engineering, teams attack all aspects of
product development simultaneously (Fig. 2).
Fig. 2: Product development 1990s style 
With this engineering model, the Conceptual design, Detailed design,
Analysis, Manufacturing preparation as well as Purchsing and Suppliers can be
considered concurrently. Most changes come in the early stages. Fewer prototypes
are needed. Therefore, a product takes less time to develop, has higher quality,
and costs less.
Computer Aided Concurrent Engineering Processes have the potential to
significantly shorten the product development cycle as has been mentioned. The
technologies involved also permit a far more thorough engineering function. For
instance, Solidification Simulation packages can accurately predict the presence
of designrelated defects such as shrinkage so that modifications to the model
can be made until a sound casting design is arrived at, even before a hard
drawing has been made. Other examples are Rapid Prototyping Processes which
offer the capability of producing accurate, scaled, hard models of castings in
just hours, which opens a wide array of possibilities in terms of optimizing
Computer-aided engineering tools and the communications afforded by computers
play key roles in the workflow of concurrent engineering. Software packages are
required for most engineering stages, such as design, analysis and prototyping.
Development issues often involved includes linkage for various packages to make
them work as one, e.g., transforing data from design package (CAD program) to
analysis tools (finite element program).
In following, several issues related to the Computer-aided Concurrent
Engineering are discussed:
- Rapid Prototyping
- Computer Aided Pattern Making
- Casting Machining
Those issues and their significance may vary for different manufacturing
Computer tools (packages) invovolved in this stages includes those for
Computer Aided Design and Solid Modeling. The Computer Aided Design tools are
primarily two-dimension drafting programs used to create engineering drawing,
while Solid modelers are highly sophisticated computer tools that allow the
"creation" on a screen, of mathematically defined solids and surfaces.
Computer Aided Design (CAD) tools permit the generation of high quality
engineering drawings in considerably less time than manual drafting methods
allow. Their greatest advantage rests in the ease with which drawing
modifications can be implemented which allows for greater flexibility in the
Although Solid modelers have the capability of producing two-dimensional
engineering drawings from the solid model, this is not their main purpose, since
that task can be better accomplished with inexpensive and simple to use PC
drafting programs. The main advantage of solid models is that they can be
manipulated as if they were actual solids. Parts can be sectioned, features
added or removed, and mass properties can be instantly computed.
Several CAD programs have capabilities for drafting parts
three-dimensionally. In effect, they generate an array of contour lines called a
"wireframe" which can give different visual perspectives of the final part. This
capability should not be confused with Solid Modeling which will be discussed
After design stage is done, manufacturing simulation, sometimes referred to
as virtual manufacturing, is performed. Production parameters, such as product
geometry, properties, defects are predicted. If the predicted results are beyond
the expection, normally design work needs to be changed (assuming the analysis
model is correct).
Finite element method (FEM) is an universal and a very powerful and most
frequently used tool for analysis. Finite differential method (FDM) is also
used, for example, for temperature prediction.
As to the analysis and its tool selection, especially of finite element
method, following aspects are of primary concern:
- Accuracy. Algorithm in the program should be optimized. With programs with
various applications, such as those general-purpose FEM programs, best-fitted
algorithm or model-type needs to be selected. For example, when both
mechanical and thermal phenomena are involved, thermo-mechanical model is
better than mechanical model. Material data (specific heat,
thermo-conductivity, etc.) and boundary conditions (heat transfer coefficient,
friction coefficients) should be entered accurately. Most of those material
data and boundary conditions are process related (e.g. temperature dependent).
- User-friendliness of program. This related to the user-friendliness of the
interface, ease and speed to generate mesh, and remeshing capability. One
fundamental requirement of simulation programs is their ability to accept
geometry from another CAD System. Although most of the solidification programs
come with their own CAD package, requirement to create solid model from
blueprints nullifies the design-to-manufacturing time cycle advantages.
- Computing time. With development of computer capacity, the computing time
may not be a crical problem any more for may processes in off-line situation.
To be noted is that the finite element analysis has a reputation for its high
computing requirement, especially for complicated processes, such as
thermo-mechanical model with large and complex plastic deformation. For
Computer Aided Concurrent Engineering, the computing time should be within an
Simulation programs can be two-dimensional or three-dimensional. Though two
dimensional programs run faster, three-dimensional ones give much accurate
results. With increased computer capability, three-dimensional programs are
Analysis tools and prediction parameters may vary for different manufacturing
processes. For casting process, for example, tools are needed to perform
- Solidification Simulation, for solidification related phonomena and
- Fluid Flow Simulation, for mold filling, gas entrapment, mold erosion and
spalling defects, slag and dross inclusions, misruns and undesirable thermal
- Mechanical Design and Stress Analysis, for mechanical and thermal
stresses, failure analysis, etc.
Rapid prototyping refers to a variety of technologies that are capable of
automatically generating physical models using solid modeling data. These
processes take place virtually unattended and complex configurations can be
produced in a matter of hours, while conventional, manual fabrication methods
can take weeks and even months to produce a complete model. The availability of
hard models at the initial stages of product development, leads to the
production of better designs and manufacturing methods since all the engineering
functions are greatly facilitated by the visualization and manipulation of hard
Computer Aided Pattern Making
This refers to the ability to use the model to generate CNC or NC machining
programs that will produce complete or partial pattern tooling from solid wood
or metal in automatic machining centers.
One major concurrent engineering advantage while using CAD models is that of
being able to generate machining methods and programs at an early design stage.
This is commonly done, for example for casting, by "merging" a rough casting
model with all the machining stock, solid cast drilled areas, etc. with a "fully
machined" finish part model using a CAD/CAM machining program. Stock to be
removed is highlighted, and the machining programmer is guided through the
definition of various operations, tool-path design, tooling selection, etc. The
CAD/CAM output is then processed through software that generates the machining
Traditional Serial engineering is still used in some instances for the
- Simple designs can be rapidly and thoroughly evaluated by foundry and
manufacturing professionals without the use of expensive and elaborate CAD/CAM
- The generation of solid models can be a lengthy and involved process that
requires well-trained specialists: in many cases a two-dimensional
conventional blueprint is faster, more economical, and just as effective.
- The cost of Computer Aided Technologies such as Solid Modeling,
Solidification Simulation and Rapid Prototyping may be high for certain
One of the key issues is the ability to transfer solid models into various
simulation packages (as mentioned above), and to use the models with rapid
prototyping devices and pattern machining programs.
One example, Application of Concurrent Engineering in Casting, is discussed
in another paper in the category "Casting".
 ASM: Steel Castings Handbook, 6th Ed., 1995. ISBN 0-87170-556-7. Ed. By
M. Blair, T.L. Stevens.