A technique called fine laser cutting is suitable for specialized cutting requirements found in the manufacturing of medical tube tools and components. Here, the term “surgical precision” aptly applies to the need for sharp edges, contours, and patterns within edges found in tools and devices in this burgeoning field.

From surgical instruments used in cutting and biopsy, to needles containing unusual tips and side wall openings, to puzzle-chain linkages for flexible endoscopes, laser cutting provides higher precision, quality, and speed than traditional cutting techniques. In addition, new laser cutting technologies are now coming on the market, including a 5-axis motion package that gives designers freedom to cut more challenging geometries in one pass.

A key to successfully using the technology is properly integrating the system’s components into a process flow that works. The motion, laser, software, and tooling must all work together to get the needed end product.

Laser cutting benefits

Fine laser cutting is good for working on small tubes that must be cut to high dimensional accuracy because the laser light used does not have any physical presence and makes no contact with the material. It does not push, drag, or impart force that might bend a part or cause it to flex. The technique also offers minimal thermal input, with fine control over how hot the work area gets. This is important because small parts heat up quickly and might otherwise overheat or deform.

Fine laser cutting is highly focusable to about 25 microns, which is about ¼ of the width of a strand of human hair. This makes it feasible to remove the minimum amount of material to make cuts, resulting in high precision and high accuracy.

The laser cutting technology has an excellent control of pulse width, power, and focus spot size. Since the cutting tool does not touch the part, it can be oriented to make almost any shape or form. Not limited by physical cutting geometry, laser cutting can be used to make unique shapes.

Cutting with gas assist

Fiber laser cutting with gas assist is frequently used to make medical tubes and components. Here, the laser is “assisted” with a coaxial gas, typically oxygen (O₂). The technology is used for stainless steels (300 and 400 series, 17-4, 17-7); MP35N (cobalt-chrome steel alloy); and Nitinol. The method works in both on-axis (90º to surface) and off-axis (angled to surface) cutting.

A highly focused laser is used to melt a thin sliver of material. While the material is still molten, a 0.02- in- dia. gas jet nozzle that is coaxial with the laser blows away the molten material. The needed features are produced using this continual cycle of melt, then melt ejection. Distance between the laser and the material needs to be maintained precisely.

The O₂ actually serves two purposes – it blows away the molten material and also serves as a heating element, because the heated material reacts with it and heats up even more. This heat reaction adds about 30 to 50% more heating energy to the cutting area. The gas assist technique increases cut speed and improves cut quality.

Laser cutting with gas assist produces the highest cut quality and high resolution cut paths, a key focus of makers of medical tube tools and components. Dimensional accuracy is key to measuring cut quality – does the part match the print? Other considerations include the sharpness of cut edges with no burr and surface roughness (better than 12 micro in.) and no thermal damage.

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