Medical implant manufacturing demands maximum precision. A few thousandths of a millimeter are decisive in differentiating between a good part and a reject in the production process. In view of those demands, a leading manufacturer of miniature medical components is relying on the know-how of experienced vision system experts for its new laser-cutting line. The small dimensioned In-Sight® Micro vision system plays a key role in the process.
Laser-cutting is the fastest, neatest solution for high-precision machining of miniature three-dimensional objects. In the case of thin-walled parts especially, such as small tubes for medical technology applications, the virtually zero-force machining method reliably executes any desired shaping. This method can form even complex geometric structures in a matter of seconds.
One of the groundbreakers in the machining of miniature medical components is ADMEDES Schuessler GmbH based in Pforzheim, Germany. ADMEDES is a world leader in the field of state-of-the-art laser-cutting technology. Its high-precision products made of nitinol—a nickel/titanium alloy with a built-in memory effect—range from stents for stabilizing blood vessels to holders for artificial heart valves.
Modern-day implant medicine would be unthinkable without lasers. The bundled light energy of lasers cuts micro-structures ultra-precisely and at an extremely high production rate. The integration of reliable inspection technology is critical to leveraging ADMEDES’ manufacturing process.
In Pforzheim, ADMEDES engineers have combined their laser know-how with state-of-the-art vision technology. This vision solution was implemented by vision systems specialist Visolution GmbH, based in Kandel, Germany. The In-Sight Micro 1403 high-resolution vision system, together with the unmatched PatMax® pattern matching vision software tool ensures precision cutting control to an unprecedented degree of accuracy using highly reliable image processing algorithms.
Ultra-precise contour recording
ADMEDES puts its high-energy laser beam source in the top section of the unit. A mirror diverts the laser beam downward vertically. The beam is extremely finely focused in the cutting die, and its bundled energy is able to form an ultra-precise, ultra-thin metal structure from the basic metal tube.
A key factor in the process is ensuring high-precision positioning and orientation of the tube that is being processed. The intelligent vision system In-Sight Micro 1403, with its high image resolution of 1600 x 1200 pixels, ensures the tube coordinates are registered to a high level of precision prior to laser-cutting. The machine then continually adjusts the object to its target position by means of the clamping jaws chuck mounted on a linear axis. This entire production process is carried out to a precision level of just a few thousandths of a millimeter.
The In-Sight Micro follows a distinct tube contour formed in an upstream processing stage. Aligned to side of the object and assisted by a telecentric light source on the opposite side, the vision system detects the characteristic contour with a high degree of precision and reliability. The telecentric light source and the vision system are mounted in the same solid framework. This special layout ensures that the two are always aligned highly precisely to each other, even despite the quite large clearance of some 80mm to the object on both sides.
In detailed imaging testing, Visolution determined the optimum mean value for the depth of focus and resolution of the components in the macro range. When the stainless steel tube is in the correct position, the laser cuts the desired contour out of the rotating object with an accuracy of +/- 3μm.
In order to manufacture miniature components to an accuracy down to thousandths of a millimeter, all components of the systems employed have to be as compact as to ensure stability.. For this reason, ADMEDES opted for the In-Sight Micro which is a compact, autonomous vision system. They were able to deploy the vision hardware in a very tight space, while still delivering maximum precision.
The In-Sight Micro system is one of the smallest intelligent vision systems in the world, measuring just 30 x 30 x 60 mm in dimensions yet is very flexible in terms of installation and delivers almost 2 MP image resolution.. The system’s non-linear calibration tools enable it to be installed even in the tightest of spaces at angles of up to 45 degrees. The unmatched image processing algorithms featured in the PatMax® tool guarantee high-precision identification and positioning of contours down to the subpixel range. The geometry-oriented functionality of PatMax is also a key factor in handling highly demanding image processing tasks and keeping manual user actions to a minimum. By analyzing the geometrical data of features and their spatial relationship to each other, it is possible to define the position of an object with extreme precision. This means features such as low-contrast contours can be detected much more reliably, precisely, and quickly. As a result, this vision system is able to offer maximum precision and reproducibility in ensuring exact localization of components and features. In conjunction with Cognex's tried and proven imaging library, these high-performance vision tools guarantee quick and easy configuration, with no need to connect to a PC.