Page 36 - MetalForming May 2014

Designing for Dollars
operation. A designer may choose to eliminate the cam and go with the sec- ond option, saving money on the ini- tial tooling investment. But how much are you really saving? If eliminating the cam can be shown to save $20,000, is doing so justified? Try simulating with and without a cam, and predict- ing the cost of both processes. Robust simulation may show that employing the cam-trim operation results in bet- ter overall production repeatability, with a 0.1-percent scrap-rate predic- tion as compared with a 0.5-percent rate by eliminating the cam. The reduc- tion in downtime due to increased repeatability could save tens or hun- dreds of thousands of dollars over the life of the job. You saved $20,000 upfront but spent perhaps $100,000 more overall. What was the correct decision?
“The future goes beyond feasibility simulation,” Kam continues, “and uses simulation results as a factor when con- sidering the overall comprehensive cost
for forming the product in a process.” Eliminating process concepts with- out sufficient justification can be a danger when only using simulation for
feasibility, Kam cautions.
“Take, for example, a three-die
process that draws, trims and flanges,” he says. “Simulation might say, ‘yes, that works.’ Then, upon springback analysis and other testing, designers decide that they must modify the part to fit into the process window, and allow for a certain amount of part vari- ation due to striking only three times. By simulating an alternative, made pos- sible due to advancements in simula- tion technology, designers may find that part quality improves enormous- ly without modifications in a four-hit process using a cam. Not modifying the product design could save tens of thousands of dollars over what the sim- plified process saves upfront.
“So now,” Kam continues, “some designers use simulation to validate a suggestion for customers to change
the product. They might say to the cus- tomer, ‘You need a product concession for the part to be makeable, and I have simulation to prove it.’ But changing the product can cost hundreds of thou- sands of dollars in assembly costs if, for example, a carryover mating compo- nent won’t fit the new part and that component must be redesigned, too.”
The Conclusion?
“People must think in a larger, more holistic way,” Kam says. “That is the next rung on the ladder for finding cost savings through simulation. Quantify the potential costs of the tools, blank material and production. Then factor in the potential repeatability of not only the ‘leading process,’ but also those that we traditionally eliminate due to subjective opinions about costs. Final- ly, make a balanced decision about the quality, cost and repeatability of the processes we choose and those we eliminate. Many in the industry are just not there yet.” MF
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