John Bannayan explains how Glebar's innovative micro grinding and gauging systems offer medical device manufacturers proven precision, reliability and quality control during the production of components such as guide wires used in minimally invasive medical procedures.
How does one produce a wire the diameter of a human hair to a geometric length of 80cm with micron-scale precision, make it completely customisable, and then manufacture it competitively with the confidence that it will survive a trip through the human body delivering a medical device? The answer? You grind it.
For over 50 years Glebar has been using innovative centreless grinding techniques to profile guide wires used in minimally invasive medical procedures. The company's machine tools are built to a high degree of precision because the risk of not doing so is so great; the patient's life is at stake.
Surgeons have certain preferences when they perform relatively commonplace critical procedures such as a balloon angioplasty. The guide wire used to set the path for catheters and other devices has a shape on the tip end that allows it to be steered through complex arterial or vascular paths in the body. The route chosen and the destination of the wire are factors determining the geometric shape of the wire. Guide wires that travel to the brain are smaller in diameter and typically have longer geometric shapes, and some are so light at the tip that they flow with the bloodstream. Material choices are endless and dictate both the torqueability of the wire and its flexibility, adding another level of complexity to manufacturing to Six Sigma standards.
Glebar has accumulated 45 years of experience in grinding small-diameter wires to 20 microns in stainless steel or nitinol. The challenge is to give medical device companies the machine tool to create these designs in CAD and turn them into a reality. Glebar designs and builds these machine tools to satisfy different degrees of precision, as well as inspection stations to ensure quality standards are maintained.
The CAM.2 micromachining system is able to produce geometric shapes including flats, threads and hexes at the tip of a 20-micron wire. The machine uses a patented feeding mechanism that facilitates complete control of product linear velocity, axial position and rotation. The system is fully programmable using a simple human-machine interface developed by Glebar as well as an underlying G-Code programming language that extends the versatility of the machine if needed. Automatic loaders and unloaders allow this system to run unattended. In some cases, peripheral devices such as sand-blasting units, inspection gauges and wire cutters are placed in line on the machine to further reduce part hand-offs and cut manufacturing costs.
The GT-9AC centreless profile grinder uses conventional centreless methods coupled with high-speed imaging technology to track and shape a guide wire up to 16ft in length by controlling the gap between the grinding wheels. This machine is able to produce simple multi-taper as well as concave or convex profiles rapidly while maintaining micron diameter precision. The unique vision system is able to track the guide wire in real time and vary the gap between the grinding wheels to produce a fully programmable shape at speeds of 25mm/second.
The P4K inspection station allows quality control to rapidly scan the geometric shapes produced on these machines and quickly report pass/fail results at the same time, maintaining lot data and statistical analysis for traceability. By measuring the diameter of the wire every 0.7 microns while the wire is pulled through a laser gauge, the unit can reconstruct the shape of the wire on the screen, determine critical transition points and datums, and provide the operator with rapid quality findings. This information can be compiled into a lot report or exported to SPC systems for process capability studies. The gauge also has the ability to network directly to the grinding machines to feed back dimensional data for automatic machine correction.
For Glebar, the goal is to provide engineers with the best tools available to manufacture and inspect these critical medical devices by expanding and enhancing grinding machine tool technology.