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CMM Styli and Probe Resources - Knowledge Base
Styli Basics
Like so many manufacturing processes, the CMM measurement system is only as strong as its weakest link. Without the proper design and quality styli purchased, the system can produce measurements that can do more harm than good.
In addition to taking care to purchase the proper and highest quality of styli and accessories, you must retain the same amount of attention and care for maintaining your equipment. Worn styli that develope flats or accumulate particulate over time must be replaced to ensure your measurements remain accurate.
- Keep styli as short as possible - this increases stability. When longer ones are required, make sure they have the required stability.
- Examine styli before use; the thread and seating area must be clear of defects to ensure a secure mount.
- A stylus that is not firmly attached is the number one cause for variations. If you experience any, make sure the thread is secure in its mount.
- When a stylus is worn, it must be replaced to prevent inaccurate measurements.
- The environment has a great effect on measurements; make sure you are using thermally stable components.
- Weight is crucial to keep in mind when assembling styli configurations. Check your machine specifications to make sure you stay within your limitations.
- Use as few pieces as possible; superfluous thread connections can cause instability and greater chances for inaccurate measurements.
- Keep in mind the different materials used in scanning styli; when scanning aluminum, silicon nitride balls are preferred.
- Use the largest ball possible. Small surface imperfections are on every workpiece, and styli with larger ball diameters scarcely record these small details, preventing random measurement variations (also called mavericks).
- Styli should be perpendicular to the workpiece. If the measuring plane is at an angle, use an angled cube or knuckle in order to ensure perpendicular alignment.
- The measuring force and dynamics should suit the probe component. Smaller styli with slimmer stems require a reduction in measuring force.