DFM Best Practices
All new medical device projects should start with a design for manufacturability (DFM) review to provide the best chance of success.
Here is our contract manufacturing checklist:
- Include your suppliers in the design process as early as possible.
- Try to start with commercially available and standard grades of material.
- Consider raw material shape and size. For example, round bar stock is more readily available than square stock and minimizing the size or your product envelope reduces overall cost significantly.
- Use machining suppliers who offer 5-axis, mill-turn, Swiss lathes or other process automation that can complete the product in one operation. This reduces setup costs, process variability, and time.
- Keep tolerances open for non-critical features. Ask your supplier for GD&T assistance and define profiles and datums that allow for both accurate and repeatable inspection.
- When prototyping, analyze tolerance stack up for assemblies in maximum and minimum material condition to ensure proper function. It is helpful to specify a functional test requirement for assemblies or a dimensional requirement for each component, but not both. Plan to review final dimensions after achieving functional performance.
- Ensure CAD files match Drawings before placing your order and use discipline with Revision controls. While RevZero does a thorough review of all documents and solid-models before releasing work to production, problems found at this stage are much more likely to blow up your project timeline.
- Consider designing checking aids for both dimensional and surface finish criteria.
- Confirm the absolute necessity for single first-article samples. If you must, establish clear acceptance and run-at-risk criteria in advance with your supplier.
- More design considerations that will save you money over and over again throughout the life of your product:
- Keep hole-depth to diameter ratios below 30:1;
- Allow for lead-in and lead-out threads;
- Ensure all surfaces are connected in CAD models;
- Use larger radii in corners
- Avoid square corners which are difficult, or impossible, to machine
- Verify that tooling exists for complex features or hard to reach areas.
Start with a few design questions or ask for feedback on some aspect of the design. RevZero uses online collaborative CAD for a design consultation or screen-share for drawing reviews. During prototyping, we often invite our customer's engineers or QA inspectors onto the shop floor to be part of the process and speed up decision-making and approvals. Ask us to send a team to your facility for cross-training where it will help ensure a smoother and more successful project.