Optimization Parameter for Micro-Gripper Based on Triple-Stair Compliant Mechanism Using GTs-TOPSIS

In manipulating the assembly of micro-components, the symmetrical microgripper mechanism often causes destruction, damaging the micro-components during manipulation. The reason is due to the phenomenon of non-uniform clamping force output of the clamp. From this disadvantage, a new asymmetric microgripper structure is proposed with stable output clamping force. The asymmetric microgripper structure will have a smaller output displacement than the symmetric structure. Therefore, to increase the output displacement gain, a flexible hinge with a triple stair half bridge-style mechanism is adopted to design the amplifier of the asymmetrical microgripper. The finite element method is applied to analyze the displacement and stress. The optimization process is performed based on the geometric parametric properties of the structure. Using the technology for order preference by similarity to ideal solution (TOPSIS) based on the grey relationship analysis (GRA) obtained the maximal displacement output and minimal stress. The results show that the maximum output displacement is 5,818 mm, stress after analysis is 2,432MPa. The test is conducted to verify the optimal results and the effectiveness of the optimization method. Finally, experimental experiments were performed, with a 4.8% difference from the FEA results. The results from the experimental test verify that the microgripper's maximum displacement amplification ratio is approximately 58.2 times.

T-Maps based Tolerance Analysis of Composites Assembly Involving Compensation Strategies

Clamping force and shimming are two important compensation processes in the composites assembly. Their effects on variation propagation should be investigated in tolerance analysis. The paper presents a tolerance analysis method for composites assembly based on the T-Maps method, mainly concerning the anisotropic variations accumulation and propagation where there is the clamping force modification and the shimming. Variations of the composite parts in different directions are represented by the T-Maps. Since the different axial deviations are represented in the same Euclidean point-space, the T-Maps based tolerance analysis of the composite parts assembly provides more accurate and reliable results. Compensation processes, the clamping force, and the shimming, on assembly tolerance synthesis of the composite parts, are analyzed clearly in the T-Map. This procedure is found to be effective for the anisotropy oriented assembly tolerance analysis, especially concerning about effect of the clamping force and the shimming on variations accumulation and propagation. The assembly of an aircraft composite elevator is considered to demonstrate the effectiveness of the T-Maps based method. The procedures outlined in the paper are quite general and can be used for assembly tolerance analysis of anisotropic parts.

Torque capacity of multidisc wet clutch with reference to friction occurrence on its spline connections

In this article developed mathematical model that includes friction occurrence on spline connections is presented. The work also contains results of experimental research on torque capacity of multidisc wet clutch. These results are expressed as a function of contact pressure for different number of friction surfaces. Due to increased interest in research concerning multidisc wet clutches it is essential to determine impact of friction on fit connections on transmitted torque. Analytical calculations that include both known loss coefficient and assumed lack of friction on fit connections are compared to results of experiments. The paper contains detailed description of test stand and methodology of experiment. As a result of conducted tests it was found that correction coefficients known from literature are highly inaccurate. Measured values of torque indicate that transmitted torque reach significantly higher values. It was also revealed that after slippage appeared, the pressure plate usually moved in the direction of exerted clamping force, but movement in reversed direction also took place for some experiments. While movement corresponding to clamping force reached ca. 0.08 mm, in opposite direction amounted to 0.02 mm. Furthermore, studies presented that lapping of adjacent friction surfaces greatly affects differences between respective results obtained for a specific experiment.

Force Control in Robotics: A Review of Applications

The aim of this article is to present an overview of the most important robotic processes in which force control methods are applied. In recent years, robotization has seen a rapid increase in the use of industrial robots in tasks that require simultaneous implementation of a given path of motion and the robot's force of interaction with the environment. In the field of industrial applications, this applies to issues related to the robotization of machining or some assembly tasks, but also the complex issue of cooperation between robots and people. One of the first applications of force control systems in robots were machining tasks such as grinding or blunting of sharp edges. Currently, robots are used in the following types of machining: grinding, polishing, chamfering, blunting, light milling. The implementation of such tasks requires the use of so-called position-force hybrid control. The task of such a control system is to implement the desired trajectory of the tool movement along the edge being machined or on the machined surface and to exert an appropriate clamping force of the tool. In the field of robotic machining, an important and still valid issue is the development and implementation of control strategies that ensure the quality of the mechanical machining process of the part despite the occurrence of unmolded phenomena, caused by, for example, significant errors in the geometry of the parts with local surface disturbances or its flexibility. Another of the basic applications of force control systems in robots are assembly tasks. In such processes, force control is particularly important, because too high interaction forces between the assembled components lead to large distortions and prevent the correct process from running. There are many papers in the literature that describe the problem of monitoring the machining process using force sensors. Monitoring the machining process is important in the industrial production of parts with a high unit cost. Any irregularity in the production of the part causing its non-compliance with the documentation is a cause of significant financial losses. Process monitoring aims to prevent irregularities during its implementation and to correct or discontinue the machining process. Friction stir welding is a method of joining materials without using consumable materials and without melting materials. In the process of friction stir welding, a cylindrical tool with a mandrel performs a rotary motion and at the same time is slowly moved along the joint area with simultaneous clamping. An industrial robot is responsible for the movement along the joint. The friction welding process is very sensitive to the temperature in the joint area. The temperature is not controlled directly, but by three other parameters: tool feed speed, tool speed and tool clamping force. For this reason, robots used for friction welding are equipped with position-force hybrid control systems. In recent years, the issue of cooperation in the human-robot system has become more and more important. The main area of application of this approach is assembly tasks. This solution has a number of advantages, such as the possibility of using the lifting capacity of the robot to lift heavy objects and the "ingenuity" of a human to maneuver the object. The robot, thanks to force sensor, is able to detect the method of maneuvering an object desired by a human. Summing up, it can be said that the use of force control has significantly increased the functionality of robotic systems in recent years.

An application system for the design of the spindle tool clamping mechanism

<p>The heart of the machining center design is the spindle design, and one of the primary functions in the spindle design is a tool clamping system mechanism. The selection of disc spring stack for a tool clamping mechanism is an iterative process that highly depends on the spindle space availability, drawbar design, tool unclamp stroke length, and standard clamping force requirements. For example, even a design space of 0.1 mm may impact one kN clamping force depending on the disc spring stack design. Hence the design of the tool clamping system for a spindle is a time- intensive process and also needed careful attention. The iterative process of disc spring stack selection may lead to an unoptimized tool clamping system, which may not be the best design. This paper explains a dynamic way to find the best spring stack selection to optimize the spindle tool clamping mechanism based on the computational application.</p>

Numerical Simulation and Process Optimization of a 3D Thin-Walled Polymeric Part Using Injection Compression Molding

Injection compression molding (ICM) is a hybrid injection molding process for manufacturing polymer products with high precision and surface accuracy. In this study, a 3D flow simulation was employed for ICM and injection molding (IM) processes. Initially, the process parameters of IM and ICM were discussed based on the numerical simulations. The IM and ICM processes were compared via numerical simulation by using CAE tools of Moldflow software. The effect of process parameters of mold surface temperature, melting temperature, compression force and injection time on clamping force and pressure at the injection location of molded 3D BJ998MO Polypropylene (MFI 100) part was investigated by Taguchi analysis. In conclusion, it was found that the ICM has a relatively lower filling pressure than ICM, which results in reduced clamping force for producing a 3D thin-walled polymeric part.