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Calibration of linear encoders has conventionally been performed using an optical interferometer for reference. Calibration using the optical interferometer, however, cannot fulfill the accuracy and stability requirements when the linear encoders exhibit sub-nanometer resolution. This study describes a new calibration method developed using the picometer resolution laser holographic scale as a reference, employing a range-dependent and minimum error-variance algorithm. The method has been evaluated via comparison tests with conventional optical-interferometer-based methods. Moreover, it has also been verified to achieve higher resolution, accuracy, and higher stability during the measurements, even in the atmospheric environment.

Sapphire capillaries manufactured with high efficiency and precision are needed for use in laser–plasma accelerators. A hybrid manufacturing process combining femtosecond laser machining and diamond tool micromilling was applied. By using a femtosecond laser mounted on a 5-axis machine, a capillary with a groove width of 630 µm and length of 90 mm was fabricated on a sapphire plate within 5 h. The surface roughness of the bottom of the cylinder groove was finished to 7.1 nm in Sa by milling with a polycrystalline diamond end mill.

Medical screws are a common mass-produced implantable medical component made of Titanium. To machine the threads of these types of components, thread whirling with carbide tools is typically used. However, tool wear and low cutting speed limit the productivity and increase the manufacturing cost of such medical parts. In this study, a direct motor driven thread whirling unit for an advanced Swiss-type CNC lathe was developed and it was used with advanced tool materials such as low binder content Cubic boron nitride (CBN) and Polycrystalline diamond (PCD) to find a cost-effective and more productive alternative to carbide tools.

Since binder-less polycrystalline diamond (BLPCD) has no macro cleavage planes and highest hardness, it is desirable material for micro milling tools. However, fabricating micro tools made of BLPCD by conventional method such as grinding is very time consuming due to its extremely high hardness. This paper describes the successful results obtained in our recent study on productive machining of BLPCD using femtosecond-pulsed laser (FSPL). The ablation effect of BLPCD by FSPL has been studied by conducting a series of experiments. Also, the predictability of ablation effect of FSPL when machining BLPCD has been evaluated by introducing numerical analysis model.

A study was performed to investigate the effects of the application of an atmospheric-pressure plasma jet during polycrystalline diamond (PCD) micro- end-milling. A comparison was made between SiC surfaces after milling, with and without the application of the plasma jet. The plasma jet was found to allow the formation of a high-quality surface with an average roughness ( R a ) of 0.73 nm. The proposed plasma jet is highly effective in improving both the chip formation process, by imparting hydrophilicity to the tool and workpiece surfaces, and removing surface contamination at the tool edge during machining.

For productive manufacturing of an accurate small-scale wine-glass gyroscope, a hybrid fabrication process consisting of either electric discharge machining, chemical etching, or micro-mechanical milling have been proposed. A comparison of silicon cavity fabrication processes has been conducted in terms of productivity, quality and geometrical accuracy, aiming at the use of the cavity as a mold for creating a thin wall diamond hemisphere, which is the main component of a wine-glass gyroscope. The results have shown that the EDM process, combined with chemical etching, can yield the highest productivity but with limited shape accuracy. The use of mechanical micro-milling, while less productive than EDM and etching, produces a superior quality and geometric accuracy.

A study has been performed to understand the mechanism for generating a high quality surface on fine grain tungsten carbide dies and molds for miniature products by PCD micro end-milling operations. In order to find the best milling conditions, systematic experimental procedures have been introduced. The procedures include the preparation of various diameter single edge end-mills made of PCD (poly-crystalline diamond), sequential variation of machining conditions, and the precise setting of various instruments to observe the dynamic behavior during the machining process. By following the proposed procedures, optimum conditions for achieving the best machined surface quality have successfully been obtained.

The demand for micromachining methods for single crystal silicon has been steadily increasing. Micro tools made from polycrystalline diamond (PCD) have considerable promise in this regard. However, it has been a concern that contamination of the PCD tool surface can give rise to an increase in frictional resistance during machining, leading to degradation of the surface integrity of the workpiece. In this study, the feasibility of surface reconditioning using a specific electrochemical technique was investigated. The technique was found to be effective in removing surface contamination without causing any damage to the tool edges.

In order to develop highly stable machining processes in heavy duty milling applications, a study on the development of a high torque–high power spindle system has been conducted. The study includes the design of a new permanent magnet synchronous motor, drive system and spindle system with the designed motor, prototype of the spindle system with the designed motor and experimental evaluation of the entire system by conducting heavy duty milling of a titanium alloy. The results of the experiments show that the spindle has a high rotational rigidity under heavy duty intermittent cutting processes.

In order to create a higher torque spindle system for productive milling operations, rotational speed stability against the torque disturbance has been studied with respect to the spindle mechanical design parameters, actuator types and spindle control algorithms. The study showed a remarkable difference in the spindle rotational speed stability against torque disturbance between a spindle system equipped with an induction servo motor and a permanent magnet synchronous servo motor. The results of this study have been obtained by theoretical analysis, numerical simulation and physical experiments, and the experimental study showed that the hybrid actuation spindle achieves longer tool life.

A compact multi-purpose spindle for multi-tasking machine tools has been developed such that it can provide high power and torque for lower speed ranges while it rotates at high speeds for light duty machining. The innovative design based on the dual direct drive concept has been adopted such that the size of the spindle can stay the same as a conventional spindle of its class. For optimizing the design process, a method based on the complete virtual approach using 3D solid models has been studied and developed. Machining performance has been verified through a physical prototype.

The paper describes a three dimensional vision-based modeling system, which can efficiently and accurately construct solid models of a machining environment including the workpiece setup with jigs and fixtures on the machine table. The unique methods of the object recognition with various key technologies have been developed based on the simultaneous real and virtual stereo image processing. Since the constructed model accurately matches with the real setup, real time NC program verifications can be performed for 100% collision-free machining simulation. The prototyped system has been successfully verified by implementation on several real machining systems.

Recent strong demand for production of ultra-precision components drives the need for 5-axis super-precision machines. A design study of such a 5-axis super-precision machine, which is capable of nanometer-level precision cutting, has been conducted by searching innovative solutions to the three major problems: friction, thermal deformation, and positioning accuracy. The final design implemented the following: stiff aerostatic guideways for near frictionless motion while structural rigidity was maintained, thermally stable structures made of alumina ceramics, and smooth control of linear motor based actuation system by employing high resolution and highly responsive linear encoders and linear power amplifiers. The designed machine has been built to verify the targeted performance. Various shapes that require nanometer- accuracy have been created using the machine. The results have consistently indicated stable nanometer-level accuracy. Targeted design performance has been successfully demonstrated.

For high performance machining, it is essential to minimize the vibration of a machine tool, which is incurred due to the instantaneous acceleration/deceleration. To minimize this vibration, it is fundamentally ideal to apply the driving force at the most shock-insensitive position of the moving structure: the center of gravity. Aiming at developing unparalleled high-performance machine tool systems, the effectiveness of the Drive at the Center of Gravity (DCG) principle on vibration reduction has been studied thoroughly by analytical and experimental approaches. Based on the results obtained, a new design of the high-performance machine tools has been discussed with a special focus on the installation of DCG mechanism without sacrificing any advantages already obtained in the recent basic design rules. The paper also describes the comparative study between a machine tool based on the DCG principle and the one with a conventional driving configuration. The results obtained have shown a distinctive performance difference in machining stability.

Open Control Systems are the key enabler for the realization of modular and re-configurable manufacturing systems. The large number of special purpose machines and the high level of automation have led to an increasing importance of open control systems based on vendor neutral standards. This paper gives an overview on the past, present and future of Open Controller Architecture. After reflecting on the different criteria, categories and characteristics of open controllers in general, the CNC products in the market are evaluated and an overview on the world-wide research activities in Europe, North America and Japan is given. Subsequently the efforts to harmonize the different results are described in order to establish a common world-wide standard in the future. Due to the “mix-and-match” nature of open controllers concentrated attention must be paid to testing mechanisms in the form of conformance and interoperability tests.

An open servo control system for an intelligent CNC machine tool system has been proposed and developed. The developed system is equipped with real-time access window, through which user custom application software can monitor or modify any parameters and variables of servo system in a real time manner as a parallel session while the standard servo control is being performed. The developed system has been implemented in a CNC vertical machining center for feasibility study by integrating the software model reference adaptive control as custom application. The experimental results have successfully demonstrated the effectiveness of the open servo system.

In-process measurement of volumetric accuracy is an effective method to enhance the machine tool motion accuracy for quality machining operations. This paper describes a new three dimensional linear encoder system for measuring the on-axis volumetric accuracy of machine motion. The proposed system consists of three cross-grid grated scales with three sensor-heads, each of which includes six opto-electronic sensing elements. The system uses a noncontact scanning principle to detect six degree-of-freedom motion errors. These represent three linear and three angular displacements along a moving axis. The evaluation tests on the prototype system have successfully demonstrated the feasibility of the proposed technology.

The paper deals with the autonomous programming technology for the high speed coordinate measuring machine (CMM). In order to provide the breakthrough technology to enhance the operability of CMMs to be used for in-line measurement of mechanical parts, a new autonomous programming method which automatically generates a CMM program from the CNC program used for machining of the part is proposed. The developed technology can provide new functionality such as efficient work-in-progress measurement capability without using the CAD product model based approach.

The paper deals with the new controller for the high performance CNC machine tools. The controller proposed is referred to as “TRUE-CNC.” “TRUE” means Transparent, Transportable and Transplantable, Revivable, User-reconfigurable, and Evolving. TRUE-CNC allows the operator to achieve the maximum productivity and highest possible quality of the machined parts in a given environment with autonomous capturing of the machining operation proficiency. The TRUE-CNC controller provides intelligent functions for less-skilled operator to run the high performance machine tools as if a skilled operator does. The concept and design aspects of the system architecture and the algorithms for functions developed for the TRUE-CNC are described in the paper.

The paper deals with a study on technologies to enhance the manufacturing productivity of a product consisting of sculptured surfaces. A process planning system coupled with real time machining is proposed such that the productive machining plan and tool motion can automatically be generated once available resources and machining know-how are given for the metal cutting-EDM mixed environment. The system proposed consists of geometry feature recognition, cutting mode and tool selection, real time tool path generation with adaptive feedrate generation using concurrent real time machining simulation. The system was prototyped to verify the feasibility. Successful results were obtained.

Summary The paper deals with a study on the injection molding system for manufacturing high quality plastic products. The problems of the conventional in-line screw injection machine were analytically and experimentally studied. To solve problems, a new injection machine with the mechatronics control system was designed and developed. The developed system features a simplified pre-plasticating type mechanism with new control system using full-software closed loop servo control with neuro-fuzzy control. The developed system demonstrated an excellent stability by which a product can be manufactured with very consistent quality and accuracy for long time without human operator intervention.

Summary The paper deals with a new method for the efficient and autonomous perception and inspection of three dimensional geometry of a mechanical part. The method developed is based on a high power X-ray CT (Computer Tomography) applied image capturing and three dimensional computer image processing. The system was developed such that a geometric model of the part can automatically be reconstructed as a computer software model with newly developed algorithms which can autonomously perceive three dimensional geometry features of the part. The feasibility of the proposed method was successfuly demonstrated by the experiments using the developed system.

The paper deals with a new method for the productive machining of molds and dies which have an artistic geometry characterized by sculptured surfaces. The method developed is referred to as a “Real Time Model Reference Adaptive Control” which autonomously adjusts the optimal feedrate such that the material removal should always be maximized with respect to the capability of a given tool and a given geometry of a workpiece by using a real time simulation of a software-based cutting process model. The practical feasibility of the proposed scheme has been verified through experiments performed on the prototyped system.

In order to cope with the demands for advanced feed drive controllers, a compact full digital servo controller has earlier been proposed so that three types of motors (DC, BLDC & AC) can be controlled with one unique hardware, only by changing its software. Aiming at a higher overall performance including Cost-effectiveness a project for integrating this “Flexible Servo Controller” has been conducted. This paper describes the development of an original ASIC chip using Standard Cell technology for the very fast current loop processing which is the most critical part of the software servo control.