Comparative comparison of direct measurement methods in geometric accuracy testing of machine tools: A case study of CNC vertical milling machine.

The CNC vertical milling machine is widely used by many manufacturing industries due to its ability to produce high variety of products with moderate production quantities. The performance of machine tools determined by the quality of the product. Therefore, the machine must be checked periodically to determine its condition and its ability. Testing, an activity to check the condition of the machine tools, were done by measuring the geometric error so that the accuracy of the machine tools can be known. In general, there is more than one method of geometric accuracy testing of machine tools and each has its advantages and disadvantages. This research aims to compare the advantages and the disadvantages of geometric accuracy testing methods and its applications. Hence, maintenance operators in the industry can choose the right method. There are two kinds of methods to measure geometric errors in machine tools, namely direct measurement and indirect measurement. Direct measurement method is often used by operators to measure the geometric errors in machine tools due to its ease to use. The indirect measurement method is performed by involving several axes movement to measure geometric errors and machine tools errors are determined from further examination of the resulting workpiece, making it more difficult and rarely used. The method of direct measurement could be divided into three, namely material-based instrument, laser-based instrument, and gravity-based instrument. These three methods were compared using comparative method based on seven specified criteria. The result showed that material-based instrument method is more suitable if the measurement length is less than 1600 mm and laser-based instrument method such as laser interferometer is more suitable to measure high precision machine tools and has a large dimension, above 1600 mm, like a gantry machine. [ABSTRACT FROM AUTHOR]