Dynamic errors from the robotic machining process can negatively impact the accuracy of manufactured parts. Currently, effectively reducing dynamic errors in robotic machining remains a challenge due ...to the incomplete understanding of the relationship between machining parameters and dynamic errors, especially for hexapod machining cells. To address this topic, a dynamic error measurement strategy combining a telescoping ballbar, an unscented Kalman filter (UKF), and particle swarm optimization (PSO) was utilized in robotic machining. The machining parameters, including spindle speed, cutting depth, and feeding speed, were defined using the Taguchi method. Simultaneously, vibrations during machining were also systematically measured to fully comprehend the nature of dynamic errors. Experimental results indicate that dynamic errors in a hexapod machining cell (HMC) are significantly amplified in machining setups, ranging from 4 to 20 times greater compared to those of non-machining setups. These errors are particularly influenced by machining parameters, especially for spindle speed. Furthermore, the extracted dynamic errors exhibit comparable frequency distributions, such as spindle frequency and tool passing frequency, to the vibration signals obtained at the chosen sampling rate. This expands the application and enhances the comprehension of dynamic errors for spindle and cutting tool condition recognition.
This paper proposed a systematic method to identify and compensate the geometric errors of non-orthogonal five-axis machine tools. An efficient ballbar test with a 45° wedge is designed to decouple ...the position-dependent and independent geometric errors for the non-orthogonal rotary axis. The geometric errors of translational axes are measured by step-size body diagonal tests based on a laser interferometer. After all the error items are measured, the volumetric error is precisely predicted and compensated based on the screw theory. The proposed geometric error identification and compensation strategy are experimentally verified via cone frustum tests on a DMG non-orthogonal five-axis machine.
In high speed machining, friction between the moving parts, generates heat. One of the major causes of thermal errors in linear axes is the heat generated in ball screw during operation at high ...speed. Thermal errors affect the accuracy of the linear axes and can cause a deviation from the nominal machining circular motion. The subject of this paper is to study the effects of feed velocity and ball screw Preload on the accuracy of circular motion. The temperature rise in the ball screw is measured by a laser thermometer. The errors in the linear and circular motions are measured by laser interferometer and ball bar. Training a neural network by the test results, thermal errors in all parts of a ball screw are predicted and compared with other test results.
