Nitinol Welding

Before committing to any manufacturer, it’s crucial to know how they will source Nitinol for a given project.

An Original Equipment Manufacturer’s (OEM’s) ability to supply the market with product is directly dependent on the contract manufacturer’s ability to source the raw material required to maintain continuity of supply. A sustained disruption in supply is often catastrophic for OEM’s. At a minimum, ensure the contract manufacturer will qualify and validate two sources of Nitinol for production. Any disruption in the material quality from the primary source can be quickly resolved by increasing supply from the second.

Equally important, the quality, type (sheet or tube) and characteristics of the Nitinol supplied by any given raw material producer is variable. The manufacturer who regularly sources material from many suppliers is able to best match the raw material to your design requirements and product application.

It’s important to evaluate product design specifications during the prototyping stage to identify opportunities to reduce cost without compromising the manufactured part’s intended function. Any cost-reducing design changes must be implemented prior to design freeze.

For any prospective new device design, extensive design and testing services should be available to help the design engineer perform FEA. This ability to model and simulate mechanical behavior reduces the time needed between design iterations, a critical step in the race to bring products to market.

Each manufacturing step requires the contract manufacturer to custom design that operation for any particular product design. This is done by designing, testing and refining the step using the same model and type of equipment and conditions that will be used in production. The capability to design and manufacture all shape-set tooling and fixturing for each process step in-house is essential to ensure the highest level of quality and process control.

It is important to understand if the manufacturer does this testing using equipment, experienced engineering personnel and facilities dedicated solely to process development, so it does not compete for time with products already in the production-manufacturing stream.

Producing finished Nitinol parts is a complex, multi-phase endeavor requiring years of experience and numerous manufacturing and finishing process capabilities. It is important to understand upfront if your supplier can completely manufacture your part in-house using special Nitinol processing techniques. Can they handle all manufacturing and finishing required to produce a marketable product without outsourcing any steps?

By handling all steps in the manufacturing process, the supplier can tune each step based on its knowledge of the upstream or downstream capabilities. This produces the highest level of quality assurance and process control.

A product’s fatigue and corrosion resistance are major factors in its performance. Finishing polishes, passivates, removes micro-cracks and deburrs the workpiece. There are various finishing methods. Electropolishing produces the best results for corrosion resistance and biocompatibility. The Electropolishing process can be designed to sharpen or round dimensional features to meet product requirements. Verify that the supplier will use Electropolishing and Passivation on the finishing of implants.

Closely regulated, Class 3 medical implants and devices manufactured to the highest specification are life-saving devices. One of the last steps in producing a device, dimensional inspection, is also one of the most critical to verifying a consistent, high quality component that meets design specifications. It is important to know if a supplier has the capability to provide validated, 100% dimensional inspection on each and every implant. Anything less invites risk to the patient and the OEM.

All operational process steps and tooling used to manufacture Nitinol implants must be within established and tested control limits. Validation ensures that the manufacturing process conforms to the control limits. Inspection ensures the manufacturing output does as well. Insist on 100% Automated Inspection for peak quality.

Validation must be conducted in accordance to ISO 13485:2016 standards. The contract manufacturer should employ an experienced validation engineering team to provide the strategy and protocols needed to complete all validation activities.

Additionally, the contract manufacturer should have in-house verification technologies to support validation, including:

• Metallography expertise and Scanning Electron Microscopy (SEM), which is required to verify removal of Heat Affected Zones (HAZ).
• Corrosion testing capabilities per ASTM F2129.
• Bend and Free Recovery (BFR) and Differential Scanning Colorimeter (DSC), to verify material Austenite Finish (Af), Mf, Ms, and As transformation temperatures.

The demand for smaller devices and entirely new neurovascular applications requires even more innovative manufacturing methods.

If the ability to test and produce next-generation implants is a priority, determine if the contract manufacturer has an athermal laser machining capability.

Norman Noble, Inc.’s proprietary S.T.E.A.L.T.H. Athermal Laser Technology is capable of manufacturing parts with kerf widths of .0004” with no heat-affected zone.