How Surface Roughness Will Affect Your Project
Surface roughness refers to the specific depth and contour of ridges on a surface. Why does testing surface roughness matter? Because there’s no such thing as “zero” surface roughness (i.e, a surface that is completely flat), every project will have some level of surface roughness to measure. Not being attentive to the precise level of surface roughness can have a significant impact on the overall quality of a product. For example, surface roughness can impact:
- How a surface looks
- How a surface functions
- How well a coating adheres to a surface
Consider the importance of surface roughness in the case of car part production. Car engines have parts the constantly rub up against each other, or parts that must fit together precisely. A surface that’s too rough – or not rough enough – can cause parts to wear out too soon, or create unwanted space that impacts the functionality of the engine.
You can also use a surface roughness measurement to detect abnormalities and defects in a product. Surface roughness measurements can therefore be relevant at the time of production and at the quality control stage.
Every project should be measured for surface roughness, and in the case of pieces fitting into larger parts, required surface roughness will likely be stated in a blueprint from the outset.
Measuring Surface Roughness
A surface roughness measurement looks at height, depth, and interval of ridges. There are ideal surface roughness for different types of materials, and even within different grades of materials. For example, different types of steel maintain different types of surface roughness.
Surface roughness can be represented by the variable Ra. The larger an Ra number, the rougher the surface. Ra is often used as a way for manufacturers to show how different machining techniques will impact surface roughness. What Ra captures is the average roughness (the arithmetic average value of the degree to which the surface deviates above and below what’s considered flat). Another way to measure surface roughness is Rz, which is the maximum height of a surface’s profile. There’s also Rq, which is the root-mean-square deviation of a profile. Before you worry too much about crunching numbers, know that these variables can be derived using tools.
You can measure surface roughness using a “contact type” method (with tip of a stylus profiler) or “non-contact type” method (with the measurement of light). Stylus profilers physically touch the surface and use a diamond tip and balancer to run across the surface in a straight line. When the stylus encounters a ridge, the line reflects deviation, and the Ra value is calculated based on the degree of deviation from the straight line.
Of course, not every material can allow for such direct contact, nor is direct contact always the easiest, quickest, or most precise way to measure surface roughness.
One of the most popular types of non-contact methods is optical profiling, which captures millions of data points by measuring the wavelengths of light that reflect off a surface. This requires the use of an optical profiling machine, many of which can be configurable to different project sizes and measurement needs.
Regardless of whether your project warrants contact or non-contact measurement, it’s essential that surface roughness measurements are taken consistently each time, with accuracy and precision. Incorrect measurements could result in failed coating applications, inconsistent product output, decrease performance quality, and weakened durability!
Take the time to familiarize yourself with the required surface roughness and measurement techniques for your next project. For additional information and support with project surfacing, reach out to the experts at Kramer Industries today!