Complete Mechanical Design – Implantable Heart Pump Power Module

Problem

The main requirements were –

1. 1. An envelope size, height x depth x width
   2. A minimum corner radius
   3. A standard fitting.
   4. An assigned wall thickness of .020 in.
   5. Structural integrity, a complete hermetic seal, and all the standard Class III medical device requirements.

1. No firm plan to make sure all of electronics will fit the envelope within a mutually facing double-sided circuit board with 3 rigid boards connected with 4 flex sections, and a communication coil at the device equator.
2. Although accelerated HALT physical destructive testing was going to be extreme, and though all 5 molded parts would have to withstand this testing, and hold the circuit boards, capacitors and batteries in relative position to each other — all molded parts had to be produced using simple molds with no slides or moving parts, maintaining structural and assembly integrity with no special features.
3. A 3-day turnaround deadline for first drafts of all 5 injection molded parts.
4. Reduced device volume — use 8 fewer square inches than the previous version of this same device.

Action

• 1. Met the initial design deadlines.
  2. Created a complex assembly that was simple and logical to assemble.
  3. The device passed all accelerated testing, including heat tests which partially melted some internal components.
  4. Redesigned injection molded parts when Electrical Engineering had to make significant mid-design battery and capacitor changes.
  5. Designed geometry to produce internal elasticity in all three dimensions to absorb component variation and battery expansion.
  6. After several electrical components interfered in the original build, I created a method for the Electrical Engineer to virtually pretest component fit and interference on populated opposite-facing circuit boards.
  7. We used 100% simple molds, benefiting from their more rapid turnaround and, of course, more favorable cost.

Result

Completed the Arrow International mechanical design on time, and even assisted the Electrical Engineering design effort.

Project Notes

This is a good example of a medical product development, start-to-finish, covering the full life of the medical device through to early production.