Lean Design with DFM

Lean from the Start

What if a process tool existed that could reduce product development cost and time to market while increasing product quality? Many product engineers and managers incorrectly believe that achieving improvements in all three areas is impossible. “It traditionally has been assumed that low price, high quality, and short lead time cannot be achieved simultaneously; that is, one goal has to be traded off against another. Recent innovations in manufacturing practices, however, indicate that the manufacturing process can be managed so that a trade-ff between these goals may not be necessary.” (Susman, 1992) Organizations leverage Design for Manufacturing as a process tool for competitive advantage creating better products faster.

What is DFM?

Design for Manufacturing is the concept of taking active consideration of realization while developing product. In other words, designing something to be made. The concept is simple yet many companies have great difficulty. DFM involves using cross-functional teams “to improve the product-process fit or to increase the degree to which the product and process are designed simultaneously.” (Susman, 1992) This requires more than a simple, cursory knowledge of the specific manufacturing processes. Organizations need experience-driven knowledge of processes working in concert as a system. Generally, this requires manufacturing personnel collaborating early in the design process. Optimally, designers (engineers) have a strong working knowledge of manufacturing systems from production experience in addition to robust process integration with manufacturing. Collaboration may generate significant objections from procurement or management as departments or vendors integrate. The objections may quiet after project gains become evident.

Techniques

Structured techniques exist for approaching DFM activities. Companies may develop a set of rules to analyze a design for problems. Software can also perform limited DFM. This approach only detects existing problems against a limited rule-set. Issues are generally not avoided, only discovered (reactive versus proactive).

DFM Rule Examples:

• Machining – No interior sharp corners
• Fabrication – Holes > Material thickness
• Hardware – Follow hole center to edge requirements for inserts

DFM Guidelines

Hard rules do not produce the best DFM results. A second technique involves understanding DFM guidelines. Guidelines present more flexible points of understanding, but are less concrete and require a more nuanced understanding of manufacturing systems.

Simplify – Antoine de Saint-Exupery said, “Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.” Fancy features might look impressive in CAD, but difficult geometry can seriously impair your ability to make rapid changes to a design. Keep it simple. Your functioning prototype will thank you. Avoid designing parts with features requiring specialized or non-standard tooling. Avoid relying on unfamiliar or prototypical manufacturing processes (at least without serious reservations and research).

Ease – Keep dimensional tolerances, including geometric tolerance, within reasonable expectations for the desired processes. Overly restrictive tolerances are a significant cost driver. Over-reliance on tight tolerances may result non-repeatable designs or issues during assembly. Design tolerances as loose as functionally possible and avoid tolerance stack-up issues.

Reduce – Ford reduced the number of components in his engines. This lowered the total cost, sped assembly, and ultimately contributed to the automobile as an accessible part of American life (Dennis, 2007). Combination will translate several parts into a singular part. This reduces setup and inventory costs.

Standardize – Modularity reduces the number of unique parts across product families thus reducing costs per item (overhead, prototyping, process design, etc.) and gaining some economy of scale. This holds true even in the modest lean of manufacturing systems. Methods of standardization include mirroring (left to right agnostic), adjustable (slots or holes series for example), or even configurations (similar parts with variable features driven by design tables).

Collaboration

Collaborative design process techniques, such as concurrent design/engineering, present a final, best solution. Working directly with manufacturing personnel early in the design process will proof features for existing processes, prepare for any challenges, and allow the entire team to buy into the design. Collaborative design and manufacturing techniques dramatically reduce lead times (Susman, 1992). Manufacturing knowledge requires years of experience to gather and understand. No software or rule-set can replace the expert knowledge experience provides.

Benefits of DFM

Companies engaging in product development consider DFM a competitive strategy. The benefits are numerous and allow organizations to differentiate themselves with better value.

• Lower design costs
• Less design iterations
• Faster development cycles
• Cheaper/faster prototype manufacture
• Cheaper production manufacturing (high ROI)
• Tighter integration with manufacturing
• Implementation of lean manufacturing
• Higher quality (lower defects)

Why Organizations Ignore DFM

Design for Manufacturing is part of practicing good design. If accessible manufacturing technologies cannot feasibly or affordably produce a design, the design has no value. Although the credible arguments against DFM are few, the excuses are many. The most difficult to overcome result from a corporate culture that undermines collaborative processes.

• Zero sum philosophy of business
• ”Not invented here” syndrome
• No manufacturing personnel
• DFM limits creativity argument

David Anderson provides a more comprehensive list of hurdles to overcome when implementing DFM strategies.

Summary

Design for Manufacturing is a simple concept with clear benefits. Companies can experience large value gains by collaboration with manufacturing personal. DFM enables your product to be Lean from the start.

Citations

Anderson, David M. Design for Manufacturability & Concurrent Engineering: How to Design for Low Cost, Design in High Quality, Design for Lean Manufacture, and Design Quickly for Fast Production. Cambria, CA: CIM, 2010. Print.

Dennis, Pascal, and John Shook. Lean Production Simplified. New York: Productivity, 2007. Print.

Susman, Gerald I. Integrating Design and Manufacturing for Competitive Advantage. New York: Oxford UP, 1992. Print.