Wednesday, October 4, 2017

Effective design for manufacturing requires a systems perspective during the design phase

Design for manufacturing is changing how companies approach medical device manufacturing. This is the first of a three-part series about design for manufacturing and its effect on different teams in the product development process.

Adopting a design for manufacturing (DFM) approach to product design influences the work of each member of the product development team. For best results, a systems perspective during the design phase is critical.

All product designs start with the technical team. This group typically includes research and development, design and engineering, manufacturing, quality, and supplier quality. The team’s goal is to deliver an accurate, measurable and manufacturable CAD model and drawings.

Metrology planning, manufacturing and post-processing are three key methods to achieve this goal, and have a critical effect on DFM.

Metrology planning
Metrology planning defines how features will be measured and why specific methods are chosen. There are four key elements to have in place before any metrology planning session:

1.       A fully defined CAD model
2.       Tolerance analyses for all interfaces of the component and other components it touches
3.       Functional map showing the other components and how the designed product effects them
4.       An Excel file with each feature listed, including its nominal dimension and tolerance

To start this planning process, the full technical team reviews the CAD model and works through the function of the component. This includes not only what the product does, but also how it affects the components it touches. This analysis should entail the datum reference schemes for each component and the associated tolerance analysis justification. 

Once the team understands the design intent and datum reference scheme of the component, it’s time to discuss the optimal way to measure each feature.

The team must balance inspection cost (driven by speed) and test method validation requirements (GR&R) to take advantage of DFM. This starts by determining the best way to fixture the part, and then moves through the Excel file: critical features first, then major, minor and finally negligible. Critical features will need to pass gauge studies and therefore require metrology capable of passing those studies, while negligible features do not need this level of scrutiny.

Manufacturing review
Manufacturing review follows metrology planning. This review examines each feature from the metrology Excel grid – from critical to negligible – to determine the level of manufacturing risk.

If any concerns are identified during this review, they should be communicated to the design engineer. Once the engineer has re-designed those areas of concern there is a final manufacturing review to confirm the risk profile.

Post-processing review
The last step for the technical team is reviewing any post-processing procedures and their impact on DFM. It is imperative for the design engineer to be acquainted with the design rules for each of the post-processes.

There are a variety of procedures to be considered, both large and small. Color anodizing is one example. One color is less expensive than two because of the manual labor required to mask two colors. Two colors can also be more expensive because of the narrow processing range to get those colors. These details can have a big impact on cost and time to create a final product, which influence DFM.

If you work with a manufacturing partner, it’s important to understand how their methods influence the manufacturing process and align with a DFM approach. By taking a systems perspective, design engineers can better meet design intent while minimizing cost and ensuring an on-time project launch.

Contact Lowell at (763) 425-3355 or to learn more about our DFM capabilities to improve time to market.