DFM Suggestions

All new medical device projects should start with a design for manufacturability (DFM) review to provide the best chance of success.  Here is our short list of considerations:

  1. Involve all parties (engineers, surgeons, vendor representatives, and marketing managers) in the design process as early as possible.
  2. Identify design intent, critical features, and product goals.
  3. Try to use commercially available and standard grades of material when possible.
  4. Consider the raw material shape and size.  Bar stock and flat stock come in standard sizes for most materials.  For some medical grade materials, round bar stock is easier to find than square stock.  Try to minimize the envelope size to reduce material cost and material removal time.  Ask your suppliers for recommendations. 
  5. Reduce the number of steps it takes to make a part. Use suppliers who can offer 5-axis, mill-turn, or Swiss lathes to machine the parts complete in one operation to avoid setup costs and extra handling time.
  6. Use vendors with process automation to avoid handling costs.
  7. Identify critical features and Cpk values.  Keep tolerances open for non-critical features.  Use proper GD&T or ask your vendor for assistance when in doubt.  Define profiles and datums that allow for accurate inspection.
  8. 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, during the prototyping stage.  After achieving functional performance, dimensions can be locked down.
  9. Ensure CAD files match Drawings when placing an order and use discipline with Revision controls.  RevZero does a thorough review of all documents and solid-models before releasing work to production to avoid costly slowdowns from discrepancies found during setup.
  10. When designing features: try to keep the ratio of hole depths to diameters at less than 30:1, allow for lead-in and lead-out threads, use larger radii in corners wherever possible, verify that tooling exists for complex features or hard to reach areas.

Always reach out with questions or to request assistance.  We can use online collaborative CAD for consultations or screen-sharing 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.  We will also send our team to your facility for cross-training as necessary to ensure a smooth and successful project.

Kirk O'Brien