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Parts Quality Testing: Surface Finish
One of the major drivers of frictional losses in a system ultimately resulting in surface and subsurface wear of the part is surface finish. At Northern Industrial many of our customers utilize our product as a support race for an anti-friction bearing. Because of this surface finish plays a big role in the product we produce. Northern Industrial Manufacturing has the capability of checking a variety of different scales when it comes to surface finish. The scales we can check our product to are: Ra, Ry, Rz, and Rq.
Surface finish, also known as surface topography or surface texture, is the condition of the surface of metal parts. Surface finish is defined by three characteristics: lay, surface roughness, and waviness. Surface finish is produced by any kind of machining operation. Surface finish can be measured by using contact or noncontact methods.
Northern Industrial Manufacturing ensures the surface finish is maintained throughout the production process using a series of in-process checks. At Northern Industrial Manufacturing, this attention to detail has won us awards like the GM Global Supplier Excellence Award, and ZF Supplier of the year. Our extensive array of part testing capabilities will bring your components to market on time and within budget at the highest level of quality possible. With a goal of being the automotive industry’s “go to” source for high quality parts manufacturing, we would love to provide you a competitive quote.
Measuring Surface Finish
There are many different ways to measure the surface finish of metal parts, both with and without use of contact. One of the methods that uses contact is the use of a tool called the profilometer, which looks like a stylus with a diamond tip that slides across the surface to “feel” the surface finish like a phonograph. There are more noncontact than contact methods used to measure surface finish. Among these noncontact methods are confocal microscopy, focus variation, structured light scanning, and digital holography microscopy.
The surface finish of metal parts matters because of how it affects the part’s ability to interact with other parts. In engineering, the surface finish of metal parts is specified using the ASME Y14.36M standard. The image below displays all the symbols used for the specifications for surface finish.
The surface finish of a metal part is important for its ability to impact that metal part’s performance, especially with other metal parts.
Surface Finish Testing
Surface Finish Characteristics
The image shows some of the different possible lay patterns that can exist in any metal parts.
One of the three characteristics of surface finish is lay. Lay is the predominant surface direction of fibers or strands. The lay direction is determined by the machining method used.
The second of the three characteristics of surface finish is surface roughness. Surface Roughness is the measure of spaced irregularities in the surface. A higher number indicates more of the irregularities in the surface. In engineering, this is usually what surface finish refers to.
The third of the three characteristics of surface finish is waviness. Waviness is the area of surface irregularities larger than surface roughness. For example, the surface of the part can be deflected or warped due to many different factors. These factors includes machining, heat treating, vibration, and a couple of other factors.
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