Surface Finishing for Stent Manufacturing & Nitinol Implants

Your Partner for every Surface Finishing Need

Norman Noble uses specialized and proprietary surface finishing processes during the manufacturing of medical devices and nitinol implants, aerospace components, and commercial parts.

Automated Electropolishing

This process is used for metal removal, remove stress risers, corner rounding, edge sharpening, deburring, providing high luster, removing heat effected zones and micro-cracks, and often improves product fatigue life. Norman Noble’s electropolishing (EP) process utilizes various engineered blends of acids that are designed to anodically dissolve the components of the part’s material. Other things to consider:

Electropolishing can improve fatigue life by removing cold working stresses, or heat-effected zones on the cut surfaces, smoothing stress risers, removing micro-cracks, and rounding corners.
NNI can also modify the electropolishing effect to sharpen edges and points.
The electropolishing effect when done properly, can improve a finish typically two-fold, or more if tolerances allow. i.e., a 8Ra will be reduced to a 4Ra.
Proper electropolishing can greatly reduce the possibility of bacterial growth on critical surfaces.
Typically, part designers target .0008” to .0010” inch removal per surface, if maximum fatigue life of the product is a concern.
Parts typically need to be back figured by NNI engineering to allow for the material that the customer’s design requirement needs to be removed.

Automated Passivation Line

Norman Noble’s automated passivation line improves productivity, product quality, product consistency, operational safety and reduces environmental costs compared to conventional systems that are manually controlled.

The automated passivation line is a nine tank system including loading conveyor pre-cleaning and passivation tanks, and an unloading conveyor. It’s a fully automatic system with gantry- style tank to tank movement. Parts are processed according to a preset “recipe.” Key tank parameters are monitored through the programmable controller and include alarm functions. Materials processed for passivation are 304 and 316 stainless steel, titanium, cobalt chrome and nitinol.

Pickling

Pickling is a treatment for metal surfaces that removes oxides, impurities, stains, rust or dross, which can be used for stainless steel, titanium, nitinol, Cobalt Chrome and other alloys. This is accomplished by dissolving the stain or oxide, along with the base material. This generally leaves the grain boundaries of the material exposed, and a somewhat matte and uneven surface. Pickling can be used to slightly change the parts dimensions, or chemically machine .0000” to .002”.

Automated Passivation System

Passivation treatments improve the surface condition of stainless steel, nitinol and cobalt chrome alloys by dissolving iron that has been imbedded or exposed in the surface during forming or machining. If allowed to remain, the iron can corrode and give the appearance of rust spots on the product.

Norman Noble’s automated passivation system line is capable of processing all 300 and 400 series Stainless Steels, 17-4 Stainless Steel, titanium, cobalt chrome and nitinol. Our validated processes are certifiable to AMS 2700, ASTM A967, ASTM F86. Passivation treatments also improve the surface condition of nitinol and titanium by dissolving iron that has been imbedded or exposed in the surface during forming or machining, and allowing the Nitinol or titanium to grow a thicker protective oxide layer, providing the maximum corrosion resistance. In addition, NNI can also perform passivation per: AMS-QQ-P-35 (Replaced QQ-P-35), AMS 2700, ASTM A-380, ASTM B-254, MIL-S-5002, ASTM B600.

Passivation is not a rust removal or coating process, but rather a deep cleaning with various concentrations and temperature of nitric acid or citric acid. The passivation is designed to maximize the inherent corrosion resistance of stainless steel, titanium, cobalt chrome and nitinol parts post-machining. A very clean, machined, electropolished or pickled stainless steel part automatically acquires some oxide film from exposure to oxygen in the atmosphere. While this natural passivation provides a thin protective oxide layer, it is not robust. Even if the parts are shiny and bright, stainless steel parts may still tarnish in a short time. This invisible oxide layer is found to be extremely thin, from 1 to 10 millionths of an inch. During the passivation process, an acid solution (nitric or citric) dissolves all contaminants, sulfides, and loose iron allowing the metal to grow a robust protective oxide film that completely covers all surfaces of the part to the maximum possible thickness.

Micro-abrasive Blasting for PEEK Implants

Norman Noble’s proprietary micro-abrasive blasting equipment can be used to deburr PEEK implants. Though PEEK’s biocompatibility and chemical resistant nature make it an ideal choice for medical implants, it creates challenges to the manufacturing process. Machining typically generates burrs that are cumbersome to remove manually. Norman Noble’s validated Micro-abrasive blasting can be used to eliminate this laborious process. The fine abrasive stream quickly strips off the burs without damaging the delicate features machined into the parts.

CNC Micro Bead Blasting and Aluminum Oxide Blasting

This finish provides desired surface texture and/or corner breaks, i.e., matte, rough, bright, removing slag or dross, oxide removal, and corner rounding. Varieties of different abrasives and beads are available to use, and need to be chosen for the application. Abrasive blasting is accomplished by propelling a graded abrasive media into a stream of compressed air or nitrogen, and focused thru a nozzle at a fixed positioned in relationship to the part(s). Bead Blasting is similar to abrasive blasting, except beads lightly peen, cold work, or plastic level the surface with graded beads consistent sizes.

Automated High Energy Finishing and Dry Tumbling

This process removes burrs, and/or adds luster. Rotation of the large turret creates a centrifugal force on the media and parts inside each barrel. This force compacts the load into a tight mass causing the media and parts to slide against each other, removing burrs and creating desired finishes.

Vibratory Finishing

Similar to High Energy Finishing, this process removes burrs, and/or adds luster, but with much less energy. This process uses cyclic vibration causing rotation to move the media around and thru the parts. This can be performed wet or dry.

Microburnishing

Microburnishing is like using a wire brush, but without a handle. It levels burrs, and/or adds luster through variously shaped smooth metal media rubbed on the metal surfaces. This process flattens the high spots by causing a plastic deformation flow of the metal surfaces and corners. Typically the corners will only slightly round, and exhibit displaced material compressed on the edge. Passivation is recommended post burnishing, to remove loose iron. Very little material is removed, in normal use, only a few ten thousandths of an inch off corners. This process will not remove heat affected zones. Burnishing economically improves the surface finish, and provides some work hardening of the surfaces.

Titanium Anodizing

Titanium Anodizing is often used in the metal finishing of products, especially those used in the medical device and aerospace industries. The process provides the advantages of hardening and coloring the surface of titanium components without altering the mechanical properties of the metal. Imparting lasting color to a component's surface allows the easy identification of devices and parts. The benefits of this are essential in surgical applications and in the assembly of complex electronic or mechanical devices.

Example Parts We've Manufactured

Materials and Applications

What We Make

Bioresorbable Scaffolds:
    Vascular Stent Implants - Cardio
    AAA (Abdominal Aortic Aneurysm)
    Peripheral
    Neuro
    Venous
    BTK (Below The Knee)

Transcatheter Heart Valve Implants and Frames:
    Aortic
    Tricuspid
    Mitral
    Left Atrial Appendage Closure

Neurovascular Clot Retrieval Devices
Neurovascular Stentrievers
Flow Diverters
Embolic Filters Arterial Closure Implants
Atrial Fibrillation Devices
Vena Cava Filter Implants
Renal Denervation Devices
Spinal Implants and Devices
Extremity Screw and Plate Implants and Devices
Ligament Repair Anchors and Devices

Materials We Use

Nitinol
Bioresorbable Polymers
PLLA
PLGA
Magnesium
Zinc
Titanium
Stainless
Molybdenum
Rhenium
Tungsten
PEEK
Cobalt Chrome
Quartz
Polyimide
Tantalum

Dedicated Process Development Teams

Process Development

Our experienced team of engineers work within our Process Development Centers (PDCs) to develop and validate cost-effective manufacturing methods required to produce prototype parts for our customers’ medtech product innovations.

Surface Finishing

Quality and Precision. Start to FINISH.