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:

  1. Include your suppliers in the design process as early as possible.
  2. Try to start with commercially available and standard grades of material.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. Consider designing checking aids for both dimensional and surface finish criteria.
  9. 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.
  10. 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.

Kirk O'BrienRevZero, Inc.