How do advanced micromachining technologies affect the performance of nitinol medical devices?

Advanced micromachining processes like laser cutting, electric discharge machining (EDM) and milling are key processes when fabricating nitinol medical devices. Unfortunately, each machining process alters the thermomechanical properties of nitinol. To judge how much this affects the functionality of nitinol devices, precise knowledge about the micromachining processes applied is crucial. Clearly, laser micromachining is still the most established technology to micromachine nitinol. Due to the non-contact removal of material, the workpiece remains free of mechanical force and deformation during the entire process.

Another technology being capable of processing difficult to machine materials is EDM. In contrast to laser cutting, it allows machining workpieces being up to several centimeters in thickness. EDM is mainly applied in the fabrication of orthopedic devices.

Machining nitinol by mechanical means, e.g., through grinding, milling, and turning can also be applied to fabricate medical devices. Especially, the fabrication of guide wires is a high-volume market. These technologies are easy to access, well known and available to many institutions and companies.

Besides the different advantages, each technology has its own limitations, e.g., due to thermal impact and achievable geometries. In this work, we report on our recent developments in the field of micromachining nitinol, especially in which way the respective technology affects the properties and the design of medical components. A comparative analysis of the technologies mentioned above is presented. To characterize various effects on the material, we performed testing methods as DSC, metallographic cross sections and SEM/EBSD imaging.