Recent our research

Controllin stiffness and damping of

                       mechanical systems and civil structures

 With the advancement of mechanical systems such as machine tool, automobiles, spacecraft, and so on, reduction of undesired vibration is one of most important problem. For example, vibrations occurring in machine tools and industrial robots have an adverse effect on manufacturing performance and positioning accuracy. On the other hand, vibrations generated in automobiles deteriorate the ride comfort. Elastic vibrations of flexible spacecraft cause serious failer in its operation. Also, in building structures, fatigue and failer will occur due to earthquakes with various periods. In order to solve the vibration problem, nonconventional damping systems must be developped.

 In conventional vibration damping technology, high damping material such as resin, gel, and so on, are used for reducing vibrations. In many cases, stiffness of mechanical or structural component, however, reduce when these damping materials are attached. In addition, active dampers are need to use actuators and sensors with high cost to control vibration amplitude.

 In this research, we propose an passive "structure damper cell" technology named as P-DACS (Passive - Damper with Anisotropic Composit Structure) is developped.

 P-DACS is the composite damper consisting of polymeric material and metalic material. By controlling anisotropity of stiffness, the damper's vibration mode that store high straine energy in the polymetric material can be generated. Mechanical components and machine element which are integrated P-DACS can be realized by using metal additive manufacturing technology. Stiffness and damping capacity of these components are controlled by damper design. In addition, damping of multi vibration mode increases by the integrated P-DACS cells.

Metal part

Polymer part

P-DACS

Constraction of P-DACS

Vibration mode of metal and

elastic strain distribution of polymer part

Controllable range of

Stiffness and damping of P-DACS

Improve the sophistication of mechanical system design

   by predicting dynamic characteristics of machine elements

 By using rolling machine elements, mechanical systems such as machine tool, automobile, robots and so on realize high-speed and highly precision relative motion with low cost. Typical rolling machine elements include ball screw, ball bearing, and rolling guideway. Now a days, these elements are necessary in many precision industries.

 In rolling machine elements, many rolling elements (Ball or Roller)  supports appliced force with low friction. Thus, the smooth relative rotational / translational motion can be realized. However, extreamely high contact stiffness is occured , and it causes elastic deformation of rolling elements. This deformation deteriorates the posture error of mechanical systems.

 Additionally, long-term vibrations due to elastic deformation of rolling elements is generated. These vibration becomes the reason that deteriorates positioning accuracy, generates chatter in cutting process, and also generates centrifugal whirling of high speed rotational body such as terbins. Thus, constructing the physics model of machine elements is needed for realizing high effeciency machine design process.

 In the lab,  we experimentally measure the static and dynamic load that applied to rolling elements of rolling guideway. Additionally, physical model of rolling guideway considering the nonlinear behavior such as nonlinear stiffness and friction is proposed. Nonlinear analysis of contact surfaces is important for precisely predicting the dynamic behavior of machine element and mechanical systems. Finally, these physical models are applied to finite element analysis of mechanical systems such as feed drives of machine tool.

Uniform surface modification using

                            constant force controlled burnish processing

 Surface enhancement is one of the most important methods to improve the product performance by improving the surface properties. After the conventional machining processes, the workpiece is usually processed by thermal treatment or shot peening to increase the surface hardness and fatigue strength. However, such treatments need special equipment and additional post process, which are not usually available in most work plants. Burnish processing is a cold work process that employs plastic deformation of a surface layer in order to improve surface characteristics, such as surface finish and surface properties. It could not only reduce the surface roughness, but also increase the surface hardness, fatigue strength and wear resistance of a workpiece.

 There are many factors that affect the properties of the burnished surface. The most important factor among them is the burnishing force. In the conventional burnish tool, the burnish ball is usually pressed by a spring embedded in the burnish tool. And the burnishing force is controlled by adjusting the pre-load of the spring. However, due to the characteristic of the spring and the shape of the treated surface, the burnishing force may not be stable during the whole burnishing process, which results a non-uniform modified surface.

 In this research, we focus on the constant force control during the burnishing process, a ball-burnishing tool, in which the burning force can be controlled in process, was proposed. The objective of the research is to realize the generation of uniformly distributed modified layer by burnishing process with constant force control.

 In the conventional burnishing process, the burnishing force should be preset before the process starts. By using the on machine force control system developed in this research, the burnishing force can be adjusted continuously during the process. By this means, it will be possible to process the complex surface, such as freeform surface, by compensating the burnishing force according to the features of the local surface. We are also concentrating on developing the force compensation method for burnish processing of freeform surface.

Bridging the gap of the CAD/CAM system

                                                                     for mass customization

 Currently, with the rapid expand of IoT(Internet of Things) and the trends of the globalization of manufacturing, it requires a higher competitiveness for the manufacturing industry of. Unlike the mass production system that produces the same product in a large quantity, the mass customization, should be able to provide high quality customized product that meet the need of each individual user with short cycle time, low cost.

 In the current CAD/CAM system, in order to generate the NC program which drives the NC machine to machine the product, the CAM programmer needs to analysis the CAD model provided by the designer, and input the necessary information to the CAM software to calculate the tool path. However, the quality of the generated NC program is highly relied on the skill and experience of the CAM user. Even machining the same part, the combination of machining method, cutting tool, machining sequence, machining parameter, and jigs will be infinite. In order to machine the product efficiently and effectively, the machining process should be carefully planned and repeatedly simulated. A large amount of the lead time is necessary. In the case of mass production, once the process plan is created, the same product can be machined in the production line until the product type changes. However, in the case of mass customization, the amount of production is usually very low, even single product production. Therefore, how to reduce the manufacturing lead time for process planning became a crucial problem.

 In order to overcome such problem, and create the foundation of the production system suitable for the next generation of manufacturing, we are focusing on developing the automatic process planning system, which is also called CAPP (Computer Aided Process Planning). It combines the knowledge of manufacturing, feature recognition of the computer graphics field, and artificial intelligence technology. This system will be able to analyze the CAD data, and extract the machining features instead of the human being. It will be also able to select the machine tool, machining method, machining sequence, cutting tool automatically. If all of this happens, the machine tool can be used as easy as a 3D printer. When we want to machine a product, what we need is just a CAD model and pushing the start button, all the other works will be finished by the computer software automatically.

Previous our research

<Machine element & Tribology>

・Influence of nonlinear friction behavior of rolling guideway

                                            on damping capacity of feed drive mechanism of machine tool

・Influence of difference in guiding system

                                            on vibrational and frictional characteristics of carrige

・Evaluation of wear characteristics with high contact force condition

                                             by insitu observation of contact surface

<Laser processing>

・Influence of laser irradiation condition on laser coloring of titanium alloy

・Fabrication of fine wire 3D structure by laser forming

・Fabrication of 3D micro structure of polymer by abration process using excimer laser

<Multi-axis machining>

・Development of automatic machining system using 8-axis robot

・Machining and coordinate measurement by polar type desktop machine tool

・Development of compensation method of posture error of 6-axis parallel work table

<Process planing & Production scheduling>

・Development of 3D-CAD based CAPP system for multi-tasking machine

・Robust production schedule system using autonomous distributed system

　We have been conducted many researches about manufacturing technology.

Please contact us if you would like to know more about our researches．