Case Study: Stapling Device Shuttle
Process: Metal injection molding
Secondary Processes: Reaming
Density: 7.75 g/cm³
Tensile Strength: 200,000 psi
Yield Strength: 160,000 psi
Hardness: 82 HRB
End Use and Function
This component is a stainless steel shuttle used in a “smart” stapling device for both open and minimally invasive arthroscopic surgery. It is part of a device that interacts with a disposable staple cartridge in a computer-controlled device that provides a high level of precision, consistency, accuracy, agility, and compressive force for the surgeon using it. Challenges included thin walls, tight radii, and true-position geometries.
Fabricated via metal injection molding (MIM), the shuttle incorporates two separate components that previously were combined via laser welding. Fabricating this intricate, small, and lightweight (5 g) component presents many challenges, including the extremely thin walls, tight radii, and true position geometries, especially the two leg tips, which need to maintain their required strength and piercing sharpness.
Part properties include 7.75 g/cm³ density, 200,000 psi ultimate tensile strength, 160,000 psi yield strength, 11%–30% elongation, and 82 HRB hardness. The shuttle is formed to nearly net shape, requiring only minimal secondary operations: reaming and then tapping the small hole, as well as providing proprietary sintering fixtures to maintain the straightness callout for the parallel walls.
- A single component instead of a two-piece component. Alternative production methods such as stamping, die casting, and sheet metal, would not be able to achieve the geometries of the MIM version of this component as a single piece.
- Cost reduction due to reduced procedure and recovery times.
- Achieved complicated geometries that other processes could not.
- MIM is a sustainable process whereas machining is not.