The directed energy deposition (DED) process has been used for enhancement of the mechanical property, repair, and part manufacturing. Post-process machining is required due to the low quality of the DED printed part. Even if the part is printed under similar conditions, dimensional variations occur frequently due to the accumulation of small printing errors. Due to tool overfeeding and the occurrence of the non-cutting area due to this variation, the quality of the finished part is not guaranteed. Therefore, the post-process machining should be carried out considering the actual printed part shape. Herein, the flexible post-process machining is proposed by utilizing the shape information through the on-machine measurement (OMM) of DED printed parts. The process margin for machining the design shape is calculated through the OMM of the geometric dimension of the printed part. Feedrate (Override) and machining path of each printing parts are flexibly determined depending on the process margin. This technique is applied to the pocket shape part printed with STS 316L material, and the rough and finish machining conditions are established. Rough machining time was reduced by adjusting the feedrate flexibly. The final form of accuracy and surface roughness were achieved under 30 and 0.25 μm, respectively.

In this research, a precise on-machine line-profile measuring system that compensates for the motion-error from the linear-guide, which can influence the accuracy of the measurement of the profile was developed. For this purpose, the principle of measuring the system model was used to analyze the compensating motion error component for line-profile and 3 types of MPES method (Integration-Method, the Fourier-Model-Method, and the Sequential-Method). The multi-probe-error-separation-method (MPES) was applied to calculate the motion-error, which in turn was used to compensate for the measured linear-profile of the specimen. Lastly, the simulation conditions involving a multi-probe measurement system consisting of a reference-artifact, capacitive-sensor, and three displacement-sensors were designed and Monte-Carlo simulation was implemented for the evaluation of the 3 types of MPES method. Also, the simulation results obtained from the conventional measuring system and the proposed system were compared for the verification of the performance of the latter. Consequently, efficient compensation of the motion error appeared as possible and the applicability of the multi-probe measurement system was confirmed.

The parallel kinematic machine (PKM), which is applied Exechon mechanism, is efficiently used for manufacturing industry due to its agile movement, flexibility and high rigidity. On-Machine measurement (OMM) in high-dof manufacturing machines such as the PKM and five-axis machine tools has importantly used for processed part measurement, coordinate system set and machine performance evaluation. In this study, measurement and compensation of touch probe offset, which occurs measurement error of the OMM, are carried out for the PKM. A dependent rotational motion is occurred due to kinematic constraint, and causes non-constant offset of a touch probe. The dependent rotational motion is calculated via inverse kinematics analysis. The probe offset is accurately measured using a master ring with considering the analyzed dependent rotational motion angle. In addition, measurement procedure to eliminate the offset induced measurement error is presented. To verify the proposed technique, circular tests using a master ring and commercial touch probe on the PKM were performed. Circularity measurement deviation of a master was reduced 65% without the PKM’s kinematic error calibration.