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This research has been conducted to develop computer aided manufacturing software, which can generate NC programs for a five-axis directed energy deposition (DED) type additive manufacturing system with following three focuses: 1. How to maintain consistent formation of a melt pool on the surface of the workpiece. 2. How to generate three-dimensional deposition path efficiently when a 3D part model is given. 3. How to control process parameters during additive operation. For focus 1, the work orientation has been controlled such that the surface to be deposited can remain perpendicular to the nozzle which is fixed to gravity direction and minimize distortion of the laser spot and powder distortion on the workpiece surface. For focus 2, a unique path generation method has been proposed based on the reverse play of a subtractive machining path, which removes the entire part to the null. For focus 3, preoperative process parameters control has been introduced to achieve the specified volumetric deposition rates along the additive tool path, which is equated with the material removal rates along the subtractive machining tool path. With methods mentioned above, the dedicated CAM system, CAMAM, has been prototyped and its feasibility has been verified experimentally by applying the NC program generation strategies to deposit several parts.

Displacement sensors based on laser or optical fiber technology are recognized for their capacity for non-contact distance measurement based on reflection from an object, but with limited measurement distance and resolution. The other option could be light wave interferometer built with the mirrors on the object. However, long distance measurement requires large laser source with stabilized-wavelength. This report presents another solution: a non-contact grating interferometer displacement sensor that enables pico-meter resolution with a semiconductor laser source.

In response to the demand for high accuracy and high resolution of angular positioning and movement of CNC machine tools, the demand for rotary encoder systems has also increased for the detection of ultra- precise angular position and movement. Authors had developed a new principle of self-calibration with multiple detecting head which enables detection of the error components of higher order with the less number of detecting heads. The system developed for this paper consists of a rotary scale with grating, sensor head unit with build-in 6 pieces of sensor heads and data processing box containing a circuit to process analog signals from the sensor head unit and output angular data applied calibration value in real time. This paper evaluates the performance of this system. In addition, the angular accuracy of the rotary encoder for servo control inside a machine tool was examined with reference to the self-calibration of the rotary encoder using the proposed method. Measured data of the accuracy of that were also utilized to generate the calibration data of the rotary encoder, and the rotary encoder was calibrated with the calibration data. The measured accuracy showed a resolution of 1/236 . It was confirmed that the angular positioning accuracy was improved because of the calibration.

Numerical error compensation is a cost-effective way to further improve the accuracy of high precision CNC machine tools. This paper discusses the major techniques for numerical error compensation on high precision machine tools. First, the high accuracy 2D holographic scale system and the dedicated measurement software are introduced. Then, the mathematical modeling of repeatable machine tool errors and the synthesis of volumetric error model are presented, followed by a description on the procedure of NC code modification. Error compensation experiments have been performed on a ballscrew driven machine tool and a linear driven machine tool. The experimental results show that numerical error compensation is generally effective on machine tools with both drive systems, while the linear driver system provides better dynamic performance for further improvement when the control precision is increased.