In The Limelight: Ra Measurements

Ra measurements

Ra is a unit of measurement that is used to express the average roughness of a surface finish. Ra measurement is especially useful because it shows the average deviation that a surface has in comparison to a mean line. However, Ra works great for general applications but faces some limitations when it comes to very specific measurements.

It also might be inadequate for machinists and quality control experts who deal with sensitive equipment. This is because any slight deviation on the surface finish can affect the performance of a part in a significant way.

Understanding How Ra Measurement Works

One of the things a machinist must understand is the relationship between the average roughness and the surface finish in general. Surfaces with varying profiles can still have a similar Ra value but the different profiles mean that these parts work differently.

For example, if a part has scratches on its surface, there is a risk that is might fracture prematurely. This calls upon machinist to ensure that they consider the surface features relative to the functionality of the part.

A More Efficient Approach to Ra Measurement

Sometimes, machinists and quality control officers recommend very tight Ra parameters in order to try and guard against scratches and peaks. This leads to a lot of wastage and is not a very efficient way of dealing with such issues.

Engineers who understand the relationship between Ra values and the surface finishes know that it is easier to clear off the peaks rather than try to use high-tolerance Ra specifications. This approach allows them to achieve the same results but in a far more economical and competitive way.

While this may sound abstract, the ability to do this makes all the difference when it comes to competitive bidding. This is because the former is able to present more competitive bids while achieving the same exact quality specifications.

Getting the Right Average Roughness

When you are machining a part, it is critical to remember that different machining processes produce different kinds of tool patterns. A good example is the roughness that comes from grinding. This is generally of a shorter wavelength as compared to turning. When a part surface undergoes milling, there are even longer wavelength patterns. Sing point boring generally produces the longest wavelength patterns.

Keep in mind that the wavelength we are talking about is the spacing between individual toolmarks and not how wavy the surface of the part is. When taking the Ra measurement values of a surface, care must be taken to ensure that the measurement is not affected by the waviness. This is done by making sure that the cut off length is short enough. At the same time, it must not be too short otherwise only a part of the tool mark is measured. Ideally, use a cutoff length that can include five complete sets of toolmarks.

Need An Excellent Mobile Roughness Tester? Try MarSurf PS 10!

With many manufacturing processes, there is always an emphasis on the quality of a product or part surface. For some products or parts, the surface finish determines how well the part functions. For example, too much roughness on a surface might weaken a part by making it more likely to crack and fail. This is especially true for parts that are subject to contact and thus friction.

Measuring Surface Roughness

The need for accurate measurements when it comes to surface roughness means that that quality control must have the right tools for the job. Not only must these products be very accurate but they must also be able to give quick results. This is because in a production setting, delays in the production line can mean loss of revenue for the organization. Sometimes the parts being measures are too heavy so they can’t be moved to the quality control room. In such cases, it becomes critical to be able to have the measurement instrument on the production floor. This reduces the time spent checking parts and thus saves the business money.

Introducing the MarSurf PS 10

The MarSurf PS 10 mobile roughness tester is one of the best in this category. The MarSurf PS 10 features state-of-the-art features such as a smartphone display that allows for easy use. The roughness tester also has internal memory for data storage but also the capacity to connect to a computer for the transfer of data. Its rechargeable data source allows for around 500 measurements and which increases its mobility. Its small size makes it very portable and very handy in a factory environment.

Other Features of the MarSurf PS 10

            •           Features a clear and adjustable display

            •           Data can be stored as TXT, CSV, X3P or PDF

            •           PDF documents can be created in the instrument

            •           Can undertake 1200 and above measurements between recharge

            •           Features a detachable drive unite

            •           Features the same number of functionalities as laboratory equipment.

            •           Has a favorites function that allows you quick access to commonly used functions

            •           Easy to use thanks to the automatic cutoff selection feature

by George Chitos

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