What is texture and how to measure it?

 

It is well-known fact that the actual surface after machining may look smooth but in reality, it is not. All the surfaces have some degree of roughness and inaccuracy. That means after machining also there are some irregularities present on the surface which cannot be seen without a microscope. While magnifying the surface, can be seen a series of peaks and valleys. Peak and valleys mean high and low in height of irregularities.

It should be noted that no surfaces can be ideal i.e. surfaces having no irregularities is impossible.

Some important terms to be considered while understanding the texture of surfaces

Roughness

Consider an ideal surface. Now the irregularities or deviation from this ideal surface is called roughness. The above fig shows irregularities on the surface.

·        Waviness

It refers to those surface irregularities which have a greater spacing than that of roughness width. That means the spacing between adjacent peaks and adjacent valleys has a greater width. It means if the width wave of irregularities is bigger, the surface will be smoother Hence, the greater the width of spacing, the smoother the surface. The thus greater width of waviness is desirable.

·        Lay

It is simply the direction or pattern of the surface. That means how waves of irregularity are arranged on the surface.

 

·        Flaw

These are the surface irregularities which are random, scratches, and crakes on the surface.

Measurement system

Measurement

This can be measured by using a mechanical device that consists of a transducer, a gauge, a processor, and a stylus with a sensing tip, also called a fingernail. Called stylus type instrument. This stylus moves over the sample length of the surface, up and down considering irregularities, and this up and down movement is converted into the signal by a transducer present. This movement generates points and sent to the processor which analyzes the data and creates a virtual profile. For accurate measurement, the gauge help to set in the straightness of the surface so that only the stylus will be touching the surface Then, this data is fed into the computer system to analyze the surface structure. The below figure shows the measurement of texture using the instrument with a stylus.

Measurement system