The popularity of surface finishing has increased over the years due to changes in regular specifications for manufacturing and dimensional tolerances which have been tightened. There are three components that will be found in a basic surface. This will include roughness, waviness, and form. The two systems that are used for surface finish measuring include skidded and skidless. These systems will be necessary for any precision machining and industrial finishing that is performed in a machine shop.
Skidded and Skidless Systems
Skidded systems will only measure the roughness of a surface. Skidless systems will evaluate the form, waviness, and roughness. Skidded gauges will have a stylus in the probe which is diamond-tipped with a skid that is resting on the workpiece. This will mean the actual workpiece is used for surface reference. A skidless gauge will use an internal precision surface for reference. Skidless systems are able to measure form, waviness, and roughness.
The high and low spots on a machined surface are the reason for irregularities. This is an issue which is caused by the grinding wheel or tool bit. The performance of the surface can often be determined along with defining any standard conditions by measuring the peaks and valleys. A variety of methods can be used measure a surface and analyze the results. One aspect of any measurement is to get the results that are the best possible for a finished surface. This means having an understanding any adverse influences that can have an effect on precision machining results.
There are a few setup conditions which will need to be met when any surface finish measurement may be needed. These include the measuring length, cutoff length, and tracing system type. Most times the use of the wrong cutoff wavelength selection is a common cause of incorrect measurements. Selection of a wrong cutoff wavelength value means the actual values may not match desired values. Cutoff length is typically dependent on reference tables that are obtained in standards. Measurement length will also be a value that is obtained in a standard. The measurement length often depends on the roughness depth or roughness spacing. Results of measurements on skidded systems are often affected by the tracing system type that is in use. The surface structure often has an effect on industrial finishing measurement values.
A number of factors will affect measurement accuracy based on the instrument which is used for surface measurement. This will include the instrument’s quality grade, the radius tip or stylus, the force applied by the stylus, the tracing speed, and the sample rate.
The normal setup for measurements includes the drive unit, the measuring stand, and tracing system. A part to be measured will be the final part of the setup. Systematic disturbances which may occur within the measuring loop is the main concern for uncertainty of a measurement. This issue is caused by a variety of different factors. There will be environmental vibrations, a part that is moving when measuring, a drive unit with guiding or driving difficulties, an improperly aligned tracing system, and surface dirt.
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