On-Machine Measurement and Error Compensation for 6061 Aluminum Alloy Hexagonal Punch Using a Turn-Milling Machine

Abstract

For machining parts with complex shapes, consisting of computer numerical control (CNC) machine tools, different CNC machine tools will be used according to the machining method. If the workpiece is removed for off-machine measurement after machining, when the size is incorrect, it will need to be returned to the CNC machine tool for secondary machining. In this case, the workpiece surface quality and machining accuracy will be affected, which is very time-consuming. On-machine measurement and complex machine center is a key to solve this problem. In the recent researches that the touch probe was integrated on three or five axis machine for error compensation and shape construction based on on-machine measurement, but turning-milling machine was rare. In addition, the most types of parts were thin-walled parts or thin web parts. In this study, a contact measurement system is integrated into a CNC combined turning-milling machine for on-machine measuring. Macro-programming is used to design the machining path of A6061-T6 aluminum alloy hexagonal punch, and the action of probe measurement is added to the machining path. As the measured data exceed the tolerance range, the calculated data are fed back to the controller for machining improvement by compensation. The finished hexagonal punch is measured in a 3D coordinate measuring machine and the error is compared. The experimental results show that the contact probe needs to be corrected before machining, and the size of the corrected workpiece can reach the tolerance range of ±0.01 mm. The size error of rough machining is larger than that of fined machining, and the size error of rough machining will increase with the length of the workpiece.

On-Machine Measurement as a Factor Affecting the Sustainability of the Machining Process

“…In [15], it was proven that stiffness and the quality of the measured surface are factors causing incorrect measurement results. The authors of [16] reached similar conclusions, emphasizing that measurements after rough machining deviate more from actual measurements than measurements after finishing machining. These articles also emphasize the importance of the machine tool's condition and the necessity for its diagnostics.…”

“…However, it is worth noting that the measurement method can also contribute to the improvement of machining programs, thereby reducing machining time. Improving the quality of manufactured components reduces the number of corrections and scrap parts [16]. Manufacturing processes for difficult-to-machine materials are extremely time-consuming, and the characteristics of these materials lead to rapid tool wear [33].…”

Mathematics Connection Between CMM and CNC Parameter Setup

“…The paper will also focus on exemplification of advanced computational techniques for determining the simulations that are necessary for correcting the machining process [6]. The practical part of this paper consists in the design of mathematic matrix for connecting the measurement report with the CNC part machining positioning so that for each null "0" positioning to be assigned a specific correction by the CMM measurement program [7]. To carry out these calculations, the main characteristics to be followed are defined, the machining process is defined and the types of tests to be carried out are determined [5].…”