Surface Notes

This tutorial discusses a step-by-step, visual approach to surface texture measurement. The process, which is the basis of the OmniSurf3D software, allows designers, managers, process engineers and lab staff to explore surface texture. OmniSurf3D provides a common language for understanding and communicating surface texture, to help improve component performance.

Roughness control is important on many surfaces. Unfortunately, some of these surfaces can be relatively short – making it difficult to perform “traditional” roughness measurements. What if your surface isn’t that long? This post describes some available options when the evaluation length is short…as well as some things NOT to do…

Many mechanical interfaces depend on the control of “flatness.” So what do you do when presented with a simple flatness tolerance and a surface to measure? How many points does it take to accurately assess flatness on the particular sample? And, what kind of filtering/processing do we do with those points?

“Harmonic Analysis” describes things that move (or shake) back and forth. The analysis tells you how many times bumps occur in each revolution of a rotating component. In fact, harmonic analysis actually looks at every frequency (every UPR) and reports how tall the bumps are for each of them. That’s a powerful analysis.

The debate over measurement of roundness is centered around the tip radius and filtering used in the measurement. This debate is complicated by the fact that typical roundness graphs distort reality. Check out this post to learn more about the relationship between surface waveforms and tip radius, and what the debate is all about.

This post includes an excellent animation (based on Digital Metrology’s training materials) that shows how the roughness and waviness profiles change with a changing filter cutoff. It is an excellent way to visualize a vital aspect of surface texture analysis!

Ramax? Rzmax? These parameters appear on drawings but not generally in measuring systems. First off: “max” does not refer to a “maximum” or upper limit. The “max-rule” deactivates the ISO default “16% rule,” in effect saying, “No single trace on this surface is allowed to go outside this tolerance limit.” Let us explain further…

Calibration of roundness measuring systems is often misunderstood and misapplied. In roundness measuring systems “Calibration” often refers to the process of adjusting the system. Typical roundness systems come with a few extra items that can help with calibration and/or adjustment. So, can you “calibrate” with them?

In order to control a process, it is likely that you will need to see the surface. A surface texture plot is often more important than the parameter value. Many people provide profile graphs with their measurements—the good ones provide consistent, fixed scaling so that the graphs look the same between measurements.