DFM for the Long Run

Manufacturers of every size constantly strive to become more efficient and reduce the cost of manufacturing. As manufacturing processes mature, they typically do become more efficient, especially in organizations that have robust, aggressive continuous improvement cultures. These companies begin to accumulate a body of lessons learned that influence the introduction of products to the manufacturing floor.

Companies assertive with continuous improvement will capture and document these lessons, using the knowledge as a foundation for improvement. The most efficient, aggressive manufacturers will use this knowledge to influence the design process by employing design-for-manufacturability concepts.

As suggested by the name, DFM is the practice of incorporating design elements that enhance manufacturability of a part or assembly with the goal of reducing the production cost.

As shops and factories gain manufacturing experience with a part or family of parts, manufacturing engineers, machinists and toolmakers can provide insights to the designers; many of these ideas significantly impact the cost and quality of parts.

Automotive manufacturers rely heavily on DFM to reduce manufacturing costs. I witnessed DFM at work by a power steering gear manufacturer where I was employed. A power steering gear assembly has several cast components. One is the main structure—the housing—which is cast from aluminum and machined to accept the other components. Older housing designs were well-suited for final assembly into the car and extremely cost-effective but difficult to hold, which made machining them a challenge. We would often have areas on a part that were not machined or were too thin because it was not properly located in the machining fixture; all such parts ended up in the scrap bin.

Eventually, the design team adopted the practice of including cast features made specifically to interface with machining fixtures on the line. Scrap from improperly loaded parts decreased to almost none. The housing design had been successfully modified to enhance manufacturability.

In other cases, we see parts produced based on DFM from an earlier time. However, they no longer conform to advances in manufacturing technology. Such was the case with a pump impeller that my family shop produced for a famous dishwasher manufacturer.

Material Matters