Dimensions And Tolerances In Engineering
As you know that the quality control departments in production is a very important part of the manufacturing site. In this department, product specimens are controlled and measured with various tools to find out whether they inside the defined tolerances and dimensions. In measurement processes, there are some kinds of technical terms are used and if you take a part in a designing, manufacturing or quality control departments in a manufacturing site, you need to know these basic technical terms.
First of all, we need to understand the term of ‘measurement’. It can be exressed as, procedure that involves the comparison of unknown quantity with known standardized quantities that are generally accepted units. These accepted standards generally include various kinds of measurement tools that are used in measurement of parts in a manufacturing site.
In measurement, a proper unit system must be selected. As you know there are bunch of unit systems in engineering and science such as US Customary or SI International Unit Systems etc. One of these unit standards must be selected for measurement process in a manufacturing site.
Accuracy in measurement: Accuracy term in measurement means the agreement between the measured values and the true(defined) values of part’s dimensions in manufacturing. There can be positive and negative deviations from the defined value that lies inside the tolerances in which the accuracy is acceptable.
Precision in measurement: This is the term that defines the repeatablity of measurement of a part’s dimension. There can be errors that originating from various sources in measurements process. But if the repeatabity is not affected from these errors in a tough way, there is no problem in the precision of measurement.
As you understand from the illustration above and the definitions of ‘precision’ and ‘accuracy’ terms, there is a difference between them in technical mean. In such measurement techniques, these terms must be satisfied in defined measurement tolerances.
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