A 'Cure' for an In-Body Camera Housing Challenge
By F. Brian Holmes, CMfgE
Vice President and General Manager
Columbia Plastics Ltd.
Surrey, BC, Canada
Medical manufacturing suppliers are expected to be able to innovate while maintaining required quality and safety standards. Quality controls are as important as nimble problem-solving abilities. Columbia Plastics, where we focus on injection molding, knows these challenges well, as the following example shows.
Our customer came to us with the challenge of making a curved camera housing for one-time use inside the body. The camera unit is reusable and is to be inserted inside the housing. The housing must protect both the patient and the camera from any form of contamination. This prevents cross contamination between patients and also ensures the camera electronics are kept clean. The curve in the design is to provide the ability to slip into the abdominal cavity and be strong enough to maneuver and hold organs in order to see around them. The housing must also include irrigation and suction lines to enable the surgeon to see clearly. These lines must be trimmed to the correct length and angle after being connected to the standard Luer fittings.
The angle of the arc along with the camera locking feature, clamping rod and suction and irrigation lines mandated the unit be made in halves and assembled. The assembly required a clear lens, the holder rod, the irrigation and suction lines along with their Luer fittings to be hermetically sealed to the handle and to support 25 lbs (11.25 kg) on the end of the clamping rod.
In order to comply with Class 2 requirements for medical devices, we chose an ultraviolet curing adhesive that would withstand the electron beam radiation used for sterilization. No adhesive was allowed on the lens or on the side of the part so it was applied robotically to ensure a consistent volume and complete coverage. In order to avoid any adhesive leakage onto the outside of the housing it was necessary to make lightweight tooling to guide the two halves of the housing together. It was also critical to ensure the parts came together properly and completely the first time to prevent any air pockets forming in the adhesive. An air pocket could allow a failure in the seal. Since the lens was required to be made separately to ensure the optical properties it had to be assembled to the main housing as well. The fact that it sits on a perpendicular plane required a separate assembly process in order to access the sealing geometry.
To ensure complete curing of the adhesive we ran a portable ultraviolet light around the sealing area. The procedure was designed to provide the whole joint with the same exposure so the curing would be equal in all areas. The simplest way to do that was to hold the light in the same robot and follow the path of the adhesive dispensing with a suitable offset.
The holder bar was molded in a highly filled polymer to replace the originally designed stainless steel unit. This allowed for electron beam sterilization without creating radiation shadows on the part, and also reduced the weight of the assembled unit without compromising the required strength. The combined cost reduction for production and sterilization was $8 per unit.
In order to ensure proper functioning of the part in use, every unit needs to be tested to ensure the hermetic seal and physical strength requirements are met. After the part is assembled, each unit is clamped into a fixture by the clamping bar and loaded with a 30-lb (13.5-kg) weight on the end of the unit. We then confirm the hermetic seal using a test unit we designed and built to pressurize the part and detect any pressure loss. All of the testing had to be calibrated to traceable standards as well.
Once this test is completed, the unit was sealed in a vacuum-formed tray and sent for sterilization and onto the customer for distribution.
The process development for this product entailed utilizing six-sigma techniques to map the process. Failure modes and effects analysis (FMEA) was used to confirm all risks had been addressed. The evaluation of the potential risks allowed us to develop economical test methods to validate the product’s ability to function reliably in the operating theatre.
F. Brian Holmes served as SME President in 2007.
This article was first published in the 2013 edition of the Medical Manufacturing Yearbook.
Published Date : 11/21/2013