What is the difference between R a & R z ? Ra – The arithmetic average of the absolute values of the profile height deviations from the centerline. Rz – the vertical distance from the highest peak to the lowest valley within the scanned profile. You can learn more in our Surface Finish Units Dictionary. How to Convert between R a & R z ?

Ra vs Rz. Ra mostly measures average surface roughness, so it is good for general quality control and aesthetic surfaces. On the other side, Rz measures peak-to-valley variations which is important for sealing surfaces and dynamic applications.

Rz measures the height difference between the highest peak and the deepest valley, while Ra averages out the roughness across the surface. In this guide, you’ll learn the core definitions of Rz and Ra and their applications in manufacturing processes.

2021年1月6日 · Ra, or average roughness, is typically used in the United States, while Rz, or mean roughness depth, is commonly used internationally. Ra is defined as the average variation of the roughness profile from the mean line. In mathematical terms, this is the integral of the absolute value of the roughness profile, divided by the profile length.

2015年4月7日 · Ra measures the average length between the peaks and valleys and the deviation from the mean line on the entire surface within the sampling length. Rz measures the vertical distance from the highest peak to the lowest valley within five sampling lengths and averages the distances.

Ra and Rz are not comparable with another, as they are distinct measurements for different parameters. Whereas Ra is useful for understanding the overall roughness of a surface, Rz is useful for identifying extreme irregularities.

2017年1月2日 · Instead of measuring from the centerline like Ra, Rz measures the average of the 5 largest peak-to-valley differences within five sampling lengths. While Ra is relatively insensitive to a few extremes, Rz is quite sensitive since it is the extremes it is designed to measure.

2024年6月20日 · Ra and Rz measure surface roughness differently. Ra calculates the average height of all surface asperities to evaluate surface roughness, indicating the overall smoothness of the surface. Rz, however, measures the maximum height difference between the surface peaks and valleys, focusing on the degree of surface irregularity.

Ra – arithmetical mean roughness value: The arithmetical mean of the absolute values of the profile deviations (Z i) from the mean line of the roughness profile (Figure 6). Rmr(c) – material component of the profile: The fraction of a line, which, in sectioning a profile, cuts through material at a stipulated height c above the mean line ...

Rz – Average Maximum Height of the Profile. Rz doesn’t measure from the centerline as Ra does. Instead, it averages the five biggest differences between peaks and valleys over five sampling lengths. Rz is sensitive to surface variations in height because of its emphasis on extremes, making it more useful than Ra.