Challenge: The Digivent Intelligent Chest Drainage System was a commercially available CE-approved device when NextPhase won the bid to manufacture the device in the US. Costs of manufacture far exceeded projections as 50% scrap rates persisted due to the welded plastic reservoir and its plastic cover not sealing properly and failing leak testing.
Proposed Corrective Action Plan: NextPhase and our customer concluded that either the process and/or the design of the components needed to be investigated and a plan developed to improve the product. It was proposed that NextPhase would conduct a design review and identify the opportunities for improved manufacturability. The review determined that the design of the mating surfaces on the reservoir and cover were designed incorrectly for a proper seal with the required ultrasonic welding and UV bonding processes. NextPhase was at that point, contracted to redesign those components and refine the ultrasonic weld process.
Resolution: Engineers at NextPhase investigated the material properties and began to iterate designs that would allow for robust joint sealing with the required ultrasonic weld and UV bonding processes. The device's plastic molded, mating components were redesigned with thicker material at the joining surfaces and tolerances that allowed for a minor interference fit at the joints. Potential gaps at the joints of mating components were minimized, if not eliminated altogether. Welding parameters, including energy, amplitude, pressure, down speed and duration were optimized. A matrix of tool design, part design, UV bonding and ultrasound weld techniques were verified and established. The validated weld process, along with a refined UV bonding process, were implemented into a controlled manufacturing procedure. Shop floor assembly team members were trained and tested, verifying their ability to follow the new procedures. All these efforts produced robust intelligent chest drainage devices with very few leaking joints.
The new weld process and joint designs proved their value as scrap rates were reduced to 10% and production levels of up to 5,000 units per year were maintained.