VoTranAnh TV pdf Thesis for Master Degree Study on the accuracy enhancement of 3 axis coordinate measuring machine working on the shop floor Vo Tran Anh Department of Mechanical and Automotive Enginee[.]
Thesis for Master Degree Study on the accuracy enhancement of 3-axis coordinate measuring machine working on the shop floor Vo Tran Anh Department of Mechanical and Automotive Engineering Graduate School, Inje University Advisor: Prof Hyun-Chul Kim Study on the accuracy enhancement of 3-axis coordinate measuring machine working on the shop floor Vo Tran Anh Department of Mechanical and Automotive Engineering Graduate School, Inje University A thesis submitted to the Graduate School of Inje University in partial fulfilment of the requirements for the degree of Master of Engineering Advisor: Prof Hyun-Chul Kim June 2015 ABSTRACT Study on the accuracy enhancement of 3-axis coordinate measuring machine working on the shop floor Vo Tran Anh (Advisor: Prof Hyun-Chul Kim) Department of Mechanical and Automotive Engineering Graduate School, Inje University Coordinate measuring machines (CMMs) are nowadays widely used for a large range of measurement tasks These tasks are expected to be carried out with ever-increasing accuracy, speed and flexibility, as well as the ability to operate under shop floor conditions The use of coordinate measuring machines (CMMs) in traditional quality control rooms, isolated from the production floor, often proves unsuitable for effective and timely feedback on the manufacturing process The time required to collect parts from the line, take them to the quality control room, thermally stabilize them and run the inspection cycle generally is longer than the manufacturing cycle itself As a result, the process may produce a large number of non-conforming parts before corrections can be made An approach focuses on the real-time monitoring of process drifts to prevent the production of defective parts and provide essential information to optimize the process is necessary In addition, many error sources affected on CMM performance on the shop floor such as kinematic errors; thermo-mechanical error; loads; dynamic forces; motion control and control software Today, high-end CMMs with maximum permissible errors below 3mm are on the market which, if uncompensated, would have that errors of 100 µm or more For that reason, to procedure high accuracy CMMs, error compensation is always necessary -1- A main goal of this work is to deal with inaccuracy related to error sources mentioned above by focus on the modeling, error mapping, and compensation of geometric errors of the machine A new method for measuring error components of rotary axes was proposed The method are simple, effective, cost saving, which use only one interferometer with very high precision for error mapping Then the error parameters were established and easily used for numerical compensation of the machine _ Keywords: Coordinate measurement machine, geometric error, error motions, laser tracking, selfcalibration, multilateration -2- Contents ABSTRACT - 1 INTRODUCTION - 1.1 COORDINATE METROLOGY - 1.2 COORDINATE MEASURING MACHINES - 1.3 SOURCES OF GEOMETRY ERRORS - 1.3.1 Machine geometry - 1.3.2 Thermo-mechanical errors - 1.3.3 Machine dynamics - 1.4 DESCRIPTION OF PRIMARY GEOMETRIC ERRORS - 1.4.1 Component errors - 1.4.2 Location errors - 1.5 MEASURING METHODS OF GEOMETRIC ERRORS - 11 1.6 NUMERICAL COMPENSATION - 11 - PURPOSE OF STUDY - 12 - METHODS - 14 3.1 NEW METHOD FOR MEASURING GEOMETRIC ERRORS - 14 3.1.1 Sequential multilateration measurement - 14 3.1.2 Measurement algorithm for determining of measurement positions - 15 3.1.3 Determining of six error components - 17 3.2 VERIFICATION THE ALGORITHM BY SIMULATION - 19 - EXPERIMENTS AND DISCUSSION - 22 4.1 LASER TRACER - 22 4.2 MEASURING ERROR COMPONENTS OF A TWO-ROTARY AXES PROBE HEAD OF CMM MACHINES - 22 4.2.1 Introduce to probing system of CMMs - 22 4.2.2 Experiment set-up - 23 4.2.3 Results and discussion - 26 - CONCLUSION - 31 - REFERENCES - 32 - -3- List of figures Figure 1: a) Process of coordinate metrology b) System components of a CMM - - Figure 2: Component errors of a linear Z - Figure 3: Component errors of a rotary axis C - Figure 4: Location errors of a linear axis - 10 Figure 5: Location errors of a rotary C-axis - 10 Figure 6: Measured Ai point’s procedure - 15 Figure 7: Measured Ai point’s procedure re-arranged - 16 Figure 8: Coordinate system transformation - 17 Figure 9: Mathematical model for calculating component errors - 18 Figure 10: Verification procedure of the mathematical module by simulation - 19 Figure 11: Deviations between generated data and calculated data of system parameters - 21 Figure 12: Deviations between generated data and calculated data of error components - 21 Figure 13: Deviations between generated data and calculated data of error components in details - 21 Figure 14: The Laser tracer: (1) reference sphere, (2) measurement beam, (3) solid stem mounted to base plate [13] - 22 Figure 15: Probe head model - 23 Figure 16: Measurement process for C axis - 24 Figure 17: Experiment set-up for measuring C axis - 24 Figure 18: Measurement process for A axis - 25 Figure 19: Experiment set-up for measuring A axis - 25 Figure 20: Six component errors of C axis - 28 Figure 21: Six component errors of A axis - 30 - -4- List of Tables Table 1: Simulation condition - 20 Table 2: Rough position of Tracers for C axis measuring - 26 Table 3: Distances measured for C axis measuring (first offset ) - 26 Table 4: Distances measured for C axis measuring (second offset) - 27 Table 5: Rough position of Tracers for A axis measuring - 28 Table 6: Distances measured for A axis measuring (first offset ) - 28 Table 7: Distances measured for A axis measuring (second offset) - 29 - -5-