Manufacturing process can help part design

While the primary consideration of a part designer or design team is the functionality of a part, the manufacturing process and the end product can be improved significantly by taking into account various elements related to manufacturing, including machinability, tooling, assembly, desired finish and economy of production. This is especially true as parts become more complex, exotic materials become more common and CAD systems and other design protocols become more technologically advanced. New design tools, such as those based on artificial intelligence protocols, have added demands for decision-making to the overall process.

Another challenge can arise in situations in which the design function is entirely separate from manufacturing — for example, when job shops are requested to quote based on a CAD file from a manufacturer. In some cases, the part in question cannot be made based on the initial design. Different families of parts also can require completely different manufacturing strategies.

Design for Manufacturing

Fraser, Michigan-based Eifel Inc. knows these concerns well. It specializes in production and prototype tooling for automotive interiors, as well as advanced tooling for the medical and aerospace industries.

“We typically work with H13 and S7 steels for abrasive plastics,” said Richard Hecker, second-generation owner and CEO. “For more conventional plastic parts, we use a milder steel, such as P20. Our process typically starts when we get a 3D part design. After reviewing the design internally, we frequently consult with the customer on opportunities to reduce complexity and identify areas in which we could save money on the tooling. We also obtain background information on how the part will be used and the type of plastic that will be molded. We need to have a comprehensive understanding of the customer’s needs.”

A 3D image (above) is displayed of a specially designed cutting tool. Image courtesy Mitsubishi Materials U.S.A.

Designing for manufacturing often includes not only the design of a part but incorporation of part fixturing. Macro Tool & Machine Co. Inc. in LaGrangeville, New York, began as a local job shop in 1968. The company now services a nationwide customer base, including aircraft and military aerospace, medical implants and tools, sporting equipment and automotive applications.

“We work in a variety of metals, ranging from sheet metal to steels, aluminum and exotics and high-temperature steel alloys,” said CEO and President Daniel Siegel. “As a job shop, we are generally unable to ask for changes to part designs except occasionally for reduced tolerances or further specifications. For instance, customers sometimes give us CAD files without the tolerances for each hole, and that’s something we have to verify.”

The inability to change the design of customer parts has resulted in the development of fixturing that delivers precise repeatability and shortened changeover times. Knowing that such challenges were not unique to his company, he developed a line of pallet-type tooling systems, indexers, single and double vises, and pallet-mounted chucks marketed under the brand name STS, which stands for Siegel Tooling Systems. Created for small and midsize parts, the products aim to increase output while avoiding the high cost of customized fixturing.

The critical nature of the design function is most apparent in the development of specialized cutting tools.

“Special tools place a dual responsibility on the manufacturer,” said Engineering Manager Paul Ditosto of Mitsubishi Materials U.S.A. Corp. in Costa Mesa, California. “On the one hand, we have to be sure that the tool we design will perform its desired function for the customer. At the same time, we have to consider the most effective and economical means of producing it. This is further complicated by the ever-increasing number of carbide grades and specialized coatings, which have to be matched to achieve the optimum combination. To obtain the best results, we have to constantly keep in mind our customer’s manufacturing process, as well as our own. Although we can occasionally modify an off-the-shelf item, our prototype designs have to be extremely exact. And because our manufacturing facilities are located globally, the sequence of operations must be spelled out.”

It’s Complicated

The complex nature of many modern parts and the materials they are made from have expanded the considerations that come into play in designing for manufacturing. Machinability, finish, quality, tolerance, economy of production, eventual method of assembly and possible interface with other components of different materials are all elements to be taken into account.

A mold for a steering wheel is machined using P20 steel. Image courtesy of Eifel

“It’s essential that we understand what the customer is trying to do, and there are many questions that have to be asked,” Ditosto said. “These would include: Can we achieve the desired finish? Can we minimize the cycle time? What are they using now? And if this is a modification of an existing design, why do they want to alter the current design?”

Hecker also cites the necessity of extensive dialogue, not only with a customer but sometimes with its suppliers.