You've heard of the buzzwords Kaizen, Six Sigma, Lean, JIT, and others. They get into the headlines because they are touted as ways to redefine businesses and save companies. Without question, these are valuable tools that manufacturers can implement to maximize profitability. However, one of the most underused tools in the product-launch toolbox that has proven to yield significant and positive results is Design for Manufacturability — DFM.

It's overlooked and undervalued yet can add significantly to the bottom line. For example, a DFM benefit shows up indirectly in terms of improved quality and consistent delivery, as well as directly in terms of reduced costs.

Sadly, many organizations treat DFM as an asterisk on the new-product-launch road map. The million-dollar question is when in the development cycle do you engage manufacturing in DFM activities?

Unfortunately, it is easy to fall into the trap of letting manufacturing engineers evaluate designs late in their development process. The best approach is to engage manufacturers in the design right at the beginning of project. Design and manufacturing engineers must foster a symbiotic relationship for a best design, and it should start as early as the ideation stage. As a general rule, once ideas transfer out of the ideation phase and into CAD models, it is too late. After drafting an idea, an inherent level of inertia squelches the acceptance of valuable ideas from the manufacturing team. A more effective approach is to collectively brainstorm as a group that includes skilled manufacturing engineers to manifest the design at its earliest stage.

A few practical examples

These few ideas suggest what to consider in the group discussions of a DFM program.

Design for ease of assembly, speed, and simplicity. On the manufacturing floor, time is money. Design resources are essentially a fixed cost once the budget is locked. However, depending on the lifecycle and volumes of the product being designed, costs avoided or removed from the product during manufacturing are apparent over the entire life of production. Given adequate sales volumes, the amount of cumulative savings per finished good can far outweigh the cost of the design resources required to produce the savings.

Designing for ease of assembly and time considerations include incorporating component features to assist with the location and translation of parts during assembly whether it is by hand or machine. An objective is to handle components in the same orientation for each production cycle. Without some locating geometry in the component, automation would not be as feasible. In addition, component features should be designed to provide proper part orientation for nesting, fixturing, or directed assembly to ensure that assemblies can only be put together only one way. Time lost by the operator determining proper component alignment is undesirable.

Fool proof the design. It is imperative to design parts with features that prohibit them from being assembled in any other orientation than the one needed. Products are destined for disaster in mass production when components do not have inherent poka-yoke (Japanese for fool-proofing) features for critical product attributes and require that assemblers use only their own judgment in the process. Mating component surfaces, joints, or interfaces in the product design should be considered for fool-proofing. Mating parts should be designed to couple in only one orientation regardless if using hand assembly or automation.

Design for assembly consistency and repeatability. Even great engineers can create products that are impossible to process consistently and repeatedly. Avoid variation at all costs when considering component and process stability, and reproducibility. Choose design options that eliminate or minimize component and process variation.

For example, if a design requires coupling two injection-molded components, the design team should design snap-fit features into the components rather than bonding with an adhesive. Why? First, because the time to snap fit two pieces is less than applying the adhesive and curing. Second, snap fits avoid application variations such as adhesive voids, or an operator applying adhesive to the wrong place. The benefits in this example are a reduction in cycle time and labor cost, as well as reduction in cost of quality often charged to scrap and rework.

Use off-the-shelf parts instead of those custom designed and built. Design teams should make material choices and use known stable parts to minimize complexity in design and assembly. Using off-the-shelf parts can significantly reduce inventory and final assembly costs. Such components let the manufacturing operation reduce minimum order quantities and inventory storage space, and increase the number of inventory turns.

Trim the bill of material. Total product costs rise with the number of parts in the bill of material. Every design should be reviewed at regular intervals with a fresh-eyes analysis of the product to identify components that can be combined or eliminated. In addition, the design team should consistently review product requirements or goals at regular intervals to ensure that critical design features are not overlooked. These activities can eliminate a situation near launch in which a design must be modified to include an additional feature or function, or eliminate interferences because someone misunderstood the requirements.

This list of DFM activities is not all inclusive, but it describes core DFM activities for most product launches. Each item is valuable, but engaging them later in the design process diminishes their effectiveness.

Assessing the impact that design has on manufacturing is critical when considering the long term quality, costs, and delivery of a new product. Many quality, cost, and delivery issues that occur post-launch are reduced with an efficient product design. The sooner the manufacturing engineering staff is involved in the product development cycle, the better are results for the company.

Of course, manufacturing and design teams share the same goal — to maximize profitability for the company. But it is impossible to achieve this goal with each department working independent of the other. When you hear the phrase, “manufacturing will have to figure that out”, you've found a culture that keeps projects from earning maximum results. Those only come from working in a partnership capacity from the start.