Machine Design

Applying common sense to Design for Manufacturing

Rajan Ramaswamy
President and CTO
Novo Engineering Inc.
Vista, Calif.

Numerous techniques have been developed to ensure that designs are suitable for manufacturing. These methods, broadly referred to as Design for Manufacturing or DFM, are said to simplify production and assembly, eliminate unnecessary parts and tooling, improve product quality, and lower overall costs.

In our design practice, however, we have noticed a growing tendency among technical managers to push for aggressive application of DFM methods early in the design process, often even at the concept stage. This can have unintended consequences, such as designs that take longer to complete, are more complex, or even optimized more for the manufacturing vendor than for the end user. Here are a few guidelines we’ve developed to help managers and lead engineers rationally apply DFM to new-product development.

• Make sure your design engineers have a basic understanding of the intended manufacturing processes. The typical image of a design team “throwing the design over the wall to manufacturing” is a well-publicized and disturbing scenario for most managers. There is negligible risk of this actually happening if an experienced design-engineering team is on the job.
• Let the design team know early on if a manufacturing vendor has been preselected and has standard tools, stock sizes, tolerances, and so on. Competent engineers will apply this information, along with general manufacturing principles, to create a design that should require minimal tweaking before formal release for production.
• Analyze your product and understand where ease of manufacturing falls on the list of priorities. For some, such as devices that must be assembled using hard automation, it is a good idea to include the automation vendor even in preliminary design sessions. In other cases, letting the vendor attend early brainstorming sessions can hinder the process by limiting creativity and idea flows.
• Plan for progressive engagement with the vendor. Hold brief reviews during the concept stage, involve the vendor in the prototyping stages so they know where the design is heading and then, before final release, do a full-blown DFM review to optimize the design for a particular vendor.
• Remember that a manufacturer’s job is to convince their client to accept the widest possible variation in the manufactured product. This is what minimizes effort and scrap, and maximizes profit for the vendor. It is tempting simply to add the vendor-recommended standard tolerances to the list of constraints that the design team must meet. However, this may actually raise overall product costs if the design grows more complex to accommodate wide part variations. A deliberate balance between design and manufacturing risk is usually a better choice for most situations.

Every design is different, and it’s more efficient to adapt design processes to the specific needs of the project at hand than simply to apply rigid formulaic approaches. We’ve learned this the hard way through dozens of projects involving interactions with domestic and offshore vendors. The customized approach is tough to implement but keeps design engineering challenging and, in the end, yields better products.

Novo Engineering provides design-engineering and manufacturing-transition services across a range of consumer, industrial, and medical markets.

Edited by Ken Korane.

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