Peter Ulintz Peter Ulintz
PMA Technical Consultant

Design for Manufacturing

October 27, 2023
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Design for Manufacturing (DFM)—often used interchangeably with Design for Manufacturing and Assembly (DFMA)—is the process of designing parts or components for ease of manufacturing and assembly. The goal: produce a better product at a lower cost, with minimal changes after the part’s release. Simplifying, optimizing and refining the product design often accomplishes this goal. 

DFM applies to all metal forming and fabricating processes. It utilizes existing knowledge from manufacturing engineers and other production personnel with years of shop-floor experience, and with knowledge about factors in product design that streamline production, and factors that hurt shop-floor productivity. The DFM process consists of many steps, including estimating manufacturing costs, reducing the number of components, reducing the cost of assembly and production, and assessing the impact of DFM decisions on other factors such as development time, product quality and lifecycle costs.

Product lifecycleIdeally, DFM occurs early in the design process, well before the beginning of manufacturing-process design. Properly executed DFM should include all stakeholders (engineers, designers, contract manufacturers, material suppliers, etc.). The intent of this cross-functional DFM team: Challenge the design, ensuring its feasibility in service and manufacturability without unnecessary hidden costs.

Key Elements

Key elements for metal forming product DFM include, at minimum:

  • Product design requirements 
  • Product material requirements
  • Manufacturing process
  • Manufacturing tolerances.

To streamline product-design requirements, engineers strive to use as few parts as possible and call for simple shapes to enable easier, more cost-effective production. Sometimes, an efficient design may reduce cost and lead times through seemingly minor modifications, with the opposite also true. Much can go wrong when product designers don’t understand the effects of material properties on the manufacturing process. Form, fit and function requirements also significantly impact material selection and manufacturing feasibility. 

According to the American Society of Mechanical Engineers, approximately 75 percent of a product’s lifecycle cost is locked in at the design stage. The implication for product development: 60 percent of the cumulative lifetime cost is committed during the feasibility and concept-development phase. Thus the importance of conducting DFM and fully optimizing during this phase (see Product Lifecycle chart).

Product material requirements typically are selected by grade, early in the product-design process. The design engineer typically selects the grade based on performance expectations of the product, including strength, weight, stiffness, surface finish and cost. However, selecting a sheet metal grade for an automotive suspension component based only on its requirement to bend under load without permanently deforming (e.g., driving into a pothole), may not offer the best choice for forming into a die cavity to create the desired shape. 

Importantly, engineers should evaluate and address manufacturing concerns during product design, as changing the material grade or the manufacturing process after design release significantly impacts final part cost.

The manufacturing process proves critical to product success. Factors such as overall cost, material consumption, surface finish, post-processing needs and tolerances must be assessed to select the most appropriate manufacturing process.

Crucially, establish the manufacturing method as soon as possible, as the other key elements highly depend on it. The product design may offer multiple options for manufacturing. Analyze each option with overall capability as the deciding factor, not manufacturing cost. Perhaps a manufacturing process has a low production cost compared to others, but with significant overall costs due to higher tool maintenance, unplanned downtime and poor quality.

The manufacturing tolerances assigned to the product have an enormous impact on the final manufacturing process and product cost. Proper tolerance design proves critical for ensuring the intended product fit and function. Tolerance must be carefully selected to balance the need for precision with the cost of manufacturing. For example, create dimensions from specific surfaces, not from intersecting points out in space. This enables manufacture of a check fixture or gauge, and helps avoid measurements errors.

Because all processes have limitations, the manufacturing process might have to change to meet tighter specifications. In general, keep design tolerances as liberal as possible while meeting a product’s functional requirements. This reduces tooling costs, increases productivity and limits potential quality spills while easing manufacture of the product.

Absentee Stakeholders

What happens when important stakeholders such as tooling, manufacturing and material suppliers either are not available or are yet to be identified by the purchasing team? This represents the biggest challenge facing design engineers, especially those lacking manufacturing and material-properties knowledge. Early involvement for many suppliers may not occur until the product reaches full development with sourcing of all suppliers completed. In these instances, it usually is too late to make improvements for susceptible variations in material, manufacturing or operating conditions.

Metal forming companies should be involved in DFM during feasibility and the concept-development phases. If not possible due to corporate policy, customer procedure or purchasing-department strategies, consider conducting a DFM seminar or workshop for customers. This will familiarize them with metal forming process capabilities and limitations so that they can make good decisions in a metal former’s absence. Next month I will share some experiences, ideas and tips for conducting such a DFM workshop. MF

Industry-Related Terms: Die, Fixture, Form, Forming, Gauge, Manufacturability, Surface, Tolerance
View Glossary of Metalforming Terms

Technologies: Management

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