Metrology for Medical Manufacturing

ADVANCEDMETROLOGYSOLUTIONSOFFERADVANTAGESTOMEDICALMANUFACTURERS Know Your Options When Selecting a Metrology System to QC Medical Parts Author: Mark G. Arenal, General Manager, Starrett Kinemetric Engineering, Inc.

The L.S. Starrett Company - Metrology Division 26052 Merit Circle, Suite 103 Laguna Hills, CA 92653

Dimensional Metrology Systems facilitate critical measurement of medical parts, but the selection of a metrology system can be challenging. A wide range of options exist for hardware and software which can be combined to create different types of systems, sometimes at widely different costs. The systems also vary in complexity, ranging from easy-to-learn manual optical comparators to fully programmable multi-sensor CNC Systems. Many of the higher-end products are electro-mechanical metrology systems which may combine optics with precision mechanical motion, linear encoders and digital image and data processing. These systems include optical comparators, vision (or video) metrology systems and a new product category of digital comparators. A digital comparator is a vision metrology system that functions like an optical comparator, but utilizes a DXF "digital overlay" instead of traditional overlays. Depending on the application requirements, each metrology solution has its advantages. QC demands for medical parts are extremely high and warrant a close look at the most advanced metrology solutions.

The growth of plastics and polymers is exponential. Plastics are used everywhere from in consumable materials to life-saving medical devices where product quality is paramount.

FORGOING GO / NO-GO Medical parts inspection demands are increasing with tighter accuracies, traceability and the need for 100% inspection. Many manufacturers have been accustomed to using go-no-go methods of gaging, such as the use of overlays in optical measuring or functional fit gages. However, there are shortcomings associated with these methods. With overlays, operator subjectivity is a significant factor. There are fine nuances to contend with, such as on-screen placement, imprecise or worn Mylar's, magnification, complex part shapes and especially the lack of detailed, variable data. Such issues force an inspector into the realm of judgment, which varies from operator-to-operator. Fatigue and data accuracy also comes into play. Functional fit gages also present their share of challenges. The gage development process is usually lengthy and expensive, with limited flexibility when parts change. And again, no variable data is attainable in the inspection process. Moreover, both overlays and functional fit gages provide no opportunity for a comprehensive audit trail and traceability process, which is paramount in medical manufacturing.

GR&R VIA ADVANCED METROLOGY SOLUTIONS Ultimately, the goal in any good inspection program should be to attain maximum gage repeatability and reproducibility (GR&R) and in the process, provide comprehensive, data for statistical process control (SPC) and traceability.

Reliable GR&R is possible with today's non-contact video and multi-sensor systems and their advanced software. Current display readout and software measuring technology such as Metlogix M3 provides full qualitative/ quantitative profile analysis functions where an inspector can compare a part profile against a nominal CAD model and obtain an actual graphic representation of any deviation from the CAD file. The system automatically finds and tracks the edge, continuously comparing it to a 2D profile, and superimposes the edge to a CAD model. In this scenario, an operator quickly, easily and automatically collects tremendous amounts of data that are all archived and documented with date, time, lot number, job number and so on, removing operator error from the equation. Not only can 100% inspection be realized, but inspection speed and throughput can also be dramatically increased due to automated systemmeasurement routines and depending on the application, palletized multi-part fixture inspection tables. Indeed, today's technology offers far more than error prone traditional methods.

The AV Automatic Vision Metrology Systems use software to control all features of Video Edge Detection and multiple channel Fiber Optic or LED illumination.


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