Surface Treatment for Medical Parts

Micro-abrasive blasting can quickly and accurately deburr small parts used in medical device manufacturing, remove conformal coatings and texture surfaces, according to supplier Comco Inc. (Burbank, CA).

The technology uses micron-sized particles of high-grade abrasives propelled out of a small nozzle tip at high velocity to clean, cut, deburr and texture a variety of surfaces. According to Comco, the process is well-suited to medical device manufacturing operations including cleaning unwanted materials or oxidation from vascular stents, removal of polymer coatings from catheters and delicate guide wires, and texturing and deburring of tubular components. It can also be used to restore surface finishes to mold cavities and to clean and texture implantable devices including titanium bone screws, prostheses, cardiac pacemakers and defibrillators.

The MicroBlaster unit can provide fast, consistent results in either manual or semi-automated micro-abrasive blasting applications, Comco says. The company operates an Applications Lab, which can help users determine the most efficient blasting method for their application. Engineers evaluate the parts tested using different abrasive media under various conditions to determine the best process.

For medical components, micro-abrasive blasting is currently used in catheter manufacturing to remove polymer coverings from small selected areas and to remove PTFE coatings from guide wires. The process is also extremely effective at preparing surfaces to promote bond and coating adhesion using sodium bicarbonate media.

For needles and tubular components, micro-abrasive blasting can remove the “heel burr” formed during grinding. Laser-machined holes or slots in the tubing may also require deburring. Other applications include selective texturing of tube surfaces before over-molding and light abrading to impart an etched surface finish. Comco says aluminum oxide and glass bead media are most common for these types of applications.

Manufacturing of vascular stents generates undesirable material deposition on the OD and ID of the devices, as well as oxidation and discoloration. Micro-abrasive blasting is widely used by stent manufacturers to remove unwanted material without altering the intricate geometry of the devices, as well as to lightly texture the stent prior to application of special coatings. Aluminum oxide and silicon carbide are typically used for stent abrading.

Bone screws, plates and implantable prostheses often have intersecting holes or slots which are difficult to deburr by conventional means but can be deburred easily by micro-abrasive blasting, according to Comco. Texturing may also be required on these devices to promote tissue growth around the implant, and the process is said to perform this task with precision and repeatability using silicon carbide, aluminum oxide and glass bead media.

Injection molds for medical products are very expensive and require periodic maintenance to the mold cavities. The company says micro-abrasive blasting can be used to clean and restore surface finishes without introducing dimensional changes to the mold cavity. It can also remove EDM residue and texture cavity surfaces of new molds. Crushed glass, walnut shells, glass beads, and plastic media are all used for mold cleaning; aluminum oxide and silicon carbide are used for cavity texturing.

Electronic components are prominent in medical diagnostic and surgical instruments, as well as implantable devices such as cardiac pacemakers and defibrillators. Comco says micro-abrasive blasting can selectively remove silicone insulation to expose an electrical conductor on defibrillators. It can also remove excess encapsulation material from cardiac pacemakers and micro-abrade conformal coatings on printed circuit boards. The most common media for these applications are sodium bicarbonate, plastic and walnut shells.