Memry fabrication and finishing processes include complex shape-setting and heat treatment, wire EDM, laser cutting, custom grinding, joining and welding, coiling, surface finishing, coatings and platings. Taken together, the processes represent our investment in expanded capability to deliver any final or semi-finished component a customer can conceive.
Having an in-house capability for all popular fabrication and finishing processes means that Memry engineers not only have enormous practice with them, but also continue to refine them. For this reason, fabrication and finishing continue to attract increased interest, with wire EDM volume, for instance, growing fourfold in 2010.
Fabrication and finishing processes
- Shape setting and heat treatment
- Wire EDM (electro discharge machining)
- Laser cutting
- Custom grinding and machining
- Joining and welding
- Surface finishing
- Coatings and platings
- Cleanroom production
Shape setting and heat treatment
Shape setting is used to form a nitinol wire, tube, strip or sheet into components with specific geometries. Whether the nitinol is designed to provide superelasticity or shape memory, and whether it starts the process cold worked or straightened, the team may need to form the material into a new “memory” shape in subsequent steps. Engineers accomplish this by constraining the material into its new shape in a fixture and then performing a heat treatment.
For each shape setting application, the team chooses from the following heat treatment methods, each offering a different mix of control and speed balanced against component requirements and cost:
- Molten Salt Bath
- Fluidized Bed
- Air Furnace
- Heated Die
- RF Induction
- Air Convection Furnace
Wire EDM (electro discharge machining)
This technique is especially attractive for cutting features into thicker shapes of conductive materials—including nitinol.
Wire EDM is an excellent technique for machining nitinol due to its burr-free finish, minimal heat affected zone, zero workpiece force and ability to process very thick workpieces. Memry uses wire sizes from .004 – .012 inches. We recently completed a significant expansion of our wire EDM production capability.
Memry has long experience laser cutting nitinol components such as peripheral stents and vena cava filters. We offer all standard and specialty laser technologies. Both tubing and sheet can be processed, with kerfs as low as .001 inch, on our state-of-the-art equipment.
Custom grinding and machining
Due to its titanium oxide surface, nitinol is a tough, abrasive material that hardens quickly, making carbide tooling a best practice.
Facility investments at Memry have made it possible for us to grind virtually any configuration using both conventional and cutting-edge grinding equipment. The team can now produce everything from simple guidewire geometries to sophisticated grinds for any custom application, including the machining of threads, flats, radiuses and points for drills, trocars or needles. Memry also applies manual microscope grinding operations which allow for fast and efficient production of complex geometries.
Joining and Welding
Memry offers many options for joining nitinol to itself or other materials, including joining wires of different diameters, and joining nitinol wire and tube within device components.
- Within welding, the company specializes in laser, plasma, TIG and resistance, with sample operations including the sealing of nitinol tubes and the fabrication of atraumatic balls, which keep the wire ends from puncturing tissue.
- Crimping is one of the best methods to join nitinol to itself, or to dissimilar materials, and Memry technicians are particularly skilled at crimping wire-formed stents.
- Pins and mechanical locking features present still other design possibilities.
- Soldering is another effective technique for assembling nitinol to dissimilar metals. Although this technique is robust, applications are somewhat limited to geometries that allow thorough cleaning of solder residue.
- Adhesives can be an attractive option for joining nitinol to other materials. Memry employs many adhesive types (UV cure, heat cure, room temperature cure) depending on the application.
Memry specializes in the fabrication of microcoils for various medical applications, sold both as raw materials and as part of higher level assemblies per customer requirements (e.g. spring coil guidewires). Along with nitinol, Memry coil materials include stainless steel, platinum and tungsten, with wire diameters available from .001 inch.
Memry offers many surface treatment processes for nitinol components and assemblies that dramatically increase their design value.
- Chemical etch removes oxide from nitinol, including recast layers formed by laser cutting or wire EDM
- Electro-polish improves nitinol corrosion resistance by making the surface finish smoother
- Mechanical polish removes oxide or recast as well, and can be fine-tuned to make very subtle changes to the surface or to create a shiny polish
- Passivation chemically creates a titanium-rich oxide layer that improves corrosion resistance
- Slurry ID cleaning creates a smooth, clean ID surface
- Microblasting employs sand, a fine but abrasive media, to create a matte textured surface. The process removes the recast layers and can also be used to improve adhesion during downstream overmolding or bonding.
Coatings and platings
Memry is often called on to apply specialized finishes to nitinol.
PTFE and FEP are hydrophobic coatings that increase lubricity, desirable in medical applications where devices need to slide easily within the body. Unfortunately both coatings typically cure at temperatures and times that risk altering the thermo-mechanical properties of the nitinol devices they coat. As part of our ongoing investment in research, we developed a low-temperature cure PTFE that significantly reduces unintended changes to the nitinol’s thermomechanical properties while preserving lubricity.
We also use Parylene coatings, which can be applied in the tightest of spaces due to their vacuum deposition application.
We apply a variety of platings, often comprised of gold, platinum or tantalum, conferring radiopacity to make a device easier to see under fluoroscopy.
We offer cleanroom facilities to accommodate the growing need among some customers for pollutant-controlled manufacturing environments. Our Class 7 cleanrooms are available for the production and assembly of components and devices. Read more about our facilities.