9.2 SIMULATIONS OF DIE CASTING PROCESSES
135
Figure 9.3 Computer simulation of die filling during metal injection. Courtesy
of MAGMA Foundry Technologies, Inc.
material properties after solidification, shrinkage porosity, and
part distortion.
Today’s computer simulations are highly developed, producing complex graphics showing the progress of metal flow during die
filling Figure 9.3. Thermodynamic results obtained from com- puter simulations can be used to predict numerous issues, includ-
ing hot spots on the die surface prone to wear and heat checking. Such data can be used to predict regions in a component prone to
solidification shrinkage, as shown in Figure 9.4. Recent advances in computer modeling of high integrity die casting processes have
focused on the prediction of residual stresses and component dis- tortion, as shown in Figures 9.5 and 9.6.
Coupling process modeling with design simulations can yield significant returns on investment by optimizing both the manufac-
136
VALUE ADDED SIMULATIONS OF DIE CASTING PROCESSES
Figure 9.4 Computer simulation illustrating areas in the die cavity prone to
solidification shrinkage porosity. Courtesy of MAGMA Foundry Technologies, Inc.
turing process and product function prior to investments in pro- duction tooling.
9.3 APPLYING SIMULATIONS EFFECTIVELY
Although some organizations report great successes when using simulations, many organizations find little value in computer mod-
eling. Organizations can be qualitatively categorized with the re- spective effectiveness of their simulation efforts, as shown in
Figure 9.7.
4
Although few, some organizations let their simulation capabilities sit idle while others do not use simulations to any
effect, generating nothing more than pretty pictures. The majority of simulation users fall into the two middle cat-
egories. Many organizations utilize computer modeling after de- signs are completed, released, and on their way to production.
9.3 APPLYING SIMULATIONS EFFECTIVELY
137
Figure 9.5 Computer simulation showing variation in residual stress that forms
during solidification and cooling. Courtesy of MAGMA Foundry Technologies, Inc.
Under these circumstances, the opportunity is lost to optimize designs. Satisfactory and even mediocre designs are carried
through to launch unless the simulation identifies a major prob- lem. Correcting problems this late in the design cycle is costly,
often requiring complete product redesign and a rush to retool. Another large group of users complete simulations and correct
major problems prior to release but do little to optimize the design.
Organizations that benefit the most from computer modeling use simulations to optimize designs and in some cases validate
the design prior to tooling a product for production. A benefit to using simulations in this manner is improved product quality by
design as opposed to quality by inspection.
With such varying degrees of effectiveness, the common ele- ment leading to successful simulation has little to do with com-
puter models. Effective simulations are the result of good management requiring resources and up-front planning.
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VALUE ADDED SIMULATIONS OF DIE CASTING PROCESSES
Figure 9.6 Computer simulation showing component distortion exaggerated
during cooling. Courtesy of MAGMA Foundry Technologies, Inc.
9.3.1 Resources
Many organizations hold the perception that computer modeling is easy, fast, and simple requiring nothing more than the touch of
a button. Often the assignment to ‘‘computer model’’ is given to someone in addition to a full load of other duties. This approach
typically generates mediocre results at best. Computer modeling is not a substitute for engineering. Diligence must be taken in
preparing the inputs to a simulation. Although a simulation may run to completion in only a few hours, the input data may take
weeks to prepare. The common request by organizations to do modeling when an engineer has spare time is unreasonable. An
organization must commit focused manpower if simulations are to be effective.
When committing manpower, care must be taken to select the right people. A diverse skill set is required of an individual who
is to conduct any given simulation. The individual must be trained
9.3 APPLYING SIMULATIONS EFFECTIVELY
139
Number of Organizations with Similar Results
Softw are A
vailab le
b ut Not Used
Mak es Pretty Pictures
P erf
or ms Sim
ulations
after Design is Completed Predict and Correct
Prob lems Dur
ing Design
Correct Prob lems and
Optimiz e Design
Predict Prob lems
,
Optimiz e
, and V
alidate Effectiveness of Simulations
Figure 9.7 Qualitative illustration grouping the number of organizations to the
effectiveness of their simulation efforts.
in modeling as well as possess knowledge of the product’s func- tion and the processes used in manufacturing. The individual must
possess soft skills, as interaction is necessary between the design and manufacturing communities.
9.3.2 Planning
Effective use of computer simulations requires planning. Few or- ganizations, if any, have the resources to conduct simulations on
every product. Planning efforts should begin by identifying stra- tegic products. For these key products, the functions and processes
that are to be simulated must be defined. Depending on the com- plexity, multiple models may need to be run for each specific
function and process. For example, a structural component may need to have simulations run to model both stresses and fatigue
life. An additional set of simulations may be run by the high
140
VALUE ADDED SIMULATIONS OF DIE CASTING PROCESSES
integrity die casting supplier to optimize the process for the com- ponent. For each individual simulation, a goal must be defined as
well as a metric to measure success. Most product timelines clearly define the date a design must be
completed with fully dimensioned drawings and specification. When preparing a timeline, it is important to specify an earlier
date at which a design is to be ready for use in computer simu- lations. Multiple iterations of any given simulation are often nec-
essary when seeking an optimized design. Also included should be a time before design release to repeat simulations.
9.3.3 Coupling Product and Process Simulations
Often process simulations are conducted by suppliers after designs have been completed and formally sourced. In such cases, opti-
mization of the manufacturing process is limited to process parameters. The opportunity to modify the design to improve man-
ufacturability is lost.
Sharing design data with suppliers prior to design release with the purpose of conducting process simulation can result in signif-
icant improvements in manufacturability and reductions in cost during production. Formal drawings with complete dimensions are
not required to complete such activities. Raw three-dimensional computer-aided design CAD data are all that is required. In
many cases, results from the process simulation can be used to predict functional properties of the product as well.
9.4 COMMITMENT
When choosing to conduct simulations, an organization must be committed in order to be effective. Capable individuals must be
selected and dedicated to the task of computer modeling. Simu- lations must be conducted prior to the completion and release of
a design. An organization must plan for success.
9.5 A CASE FOR SHARING SIMULATION DATA
ACROSS ORGANIZATIONS
During the development of a structural component for an auto- motive chassis, a supplier and original equipment manufacturer
REFERENCES
141
OEM worked concurrently to engineer both the product and the process. Simulations were conducted by the OEM to analyze the
stresses within the component during operation. The supplier used computer modeling to develop a gate and runner system. The re-
sults of the simulations were not exchanged due to ‘‘proprietary’’ reasons. Conclusions drawn from the results, however, were
shared freely, resulting in minor changes to the design to improve function and manufacturability. At release, the partners believed
both the product and process had been optimized.
Prototypes were fabricated from production, such as tooling, for product verification tests. The initial prototypes failed. Al-
though simulations were conducted concurrently, the simulation results were never examined side by side. Comparison of the sim-
ulation results showed that two major metal fronts in the die con- verged at the point in the structure that bore the highest stresses
during operation. The process tooling was redesigned such that the two metal fronts converged at a low stress point within the
structure. Had the results of the product and process simulation been compared earlier, redesign of the process would have been
avoided.
REFERENCES
1. Robust Design Using Taguchi Methods Workshop Manual, American Supplier Institute, Livonia, MI, 1998.
2. Solutions, American Supplier Institute, Livonia, MI, 1999. 3. Clausing, D., Total Quality Development, ASME Press, New York, 1994.
4. Vinarcik, E., ‘‘Minimizing Cost Through Part Integration,’’ Engineered Cast- ing Solutions,
Winter 1999, p. 56.
