Nitinol shape setting is a process by which specified shape of the metal is configured and programmed though fixturing and heat treating. Nitinol can be shape set by wrapping nitinol wire around a mandrel or fixture of predefineced shape and heat treating at a tightly controlled time and temperature to achieve a desired shape in the material. Once programmed the nitinol shape will want to return to its "programmed" shape when manipulated. Some of the applications of this technology include trying to get teeth to move in a certain direction (i.e. braces) or trying to get the core wire of a guidewire to move as the doctor would like. Shape setting must also take into account the type of nitinol being used, which may require different processing temperatures and exhibit different characteristics. “Superelastic” and “shape memory” types of nitinol are generally available in Nitinol wire, ribbon, strip, Nitinol sheet, tubing or bar form.
The parameters for this phase transformation usually need to be determined experimentally for each part until a high level of precision and repeatability can be achieved. Advanced Medical Compnent’’s expert technicians perform all research and development tasks prior to production to insure that all shape and use requirements are met.
To set shape set nitinol, machined nitinol is constrained on a mandrel, or custom fixture. This mandrel can be made by AMC or provided by the customer. Once the nitinol is fixed on the mandrel, its shape is set with a specific heat treat. Either AMC or the customer can specify the type of heat treat used: fluidized bed, with Alumina media; convection air furnace; or salt bath furnace. Rapid cooling is then used to return the metal to its original form.
Imbedding an element of shape memory nitinol in the tip of a catheter could provide active, on-demand steering which is why it is often used in the guidewire manufacturing process. Nitinol has been proven to be effective in certain applications, namely small and/or long, flexible products for interventional identification of paths. Mechanical, pull-wire, technology competes with nitinol steering. Mechanical steering requires that the tension of the pull wires be transmitted to the tip of a catheter. In long, small OD, and flexible catheters, nitinol steering may be the only effective method which is why we work OEMs to make sure that all products are manufactured to tight specifications.
To set a nitinol shape, generally speaking, you could use temperatures as low as 400 celcius for 1-2 minutes. AMC is hold fairly precise temperatures for setting nitinol shapes. Contact us with your project to see if we can fulfill your tight specifications for heat treating and heat setting.