A Review of Thermal Error Modeling Methods for Machine Tools

Thermal error caused by thermal deformation is one of the most significant factors influencing the accuracy of the machine tool. Compensation is a practical and efficient method to reduce the thermal error. Among all the thermal error compensation processes, thermal error modeling is the premise and basis because the effectiveness of the compensation is directly determined by the accuracy and robustness of modeling. In this paper, an overview of the thermal error modeling methods that have been researched and applied in the past ten years is presented. First, the modeling principle and compensation methods of machine tools are introduced. Then, the methods are classified and summarized in detail. Finally, the future research trend of thermal error modeling is forecasted.

Design of Deformable Tools for Sheet Metal Forming

Traditionally, industrial sheet metal forming technologies use rigid metallic tools to plastically deform the blanks. In order to reduce the tooling costs, rubber or flexible tools can be used together with one rigid (metallic) die or punch, in order to enforce a predictable and repeatable geometry of the stamped parts. If the complete tooling setup is built with deformable tools, the final part quality and geometry are hardly predictable and only a prototypal production is generally possible. The aim of this paper is to present the development of an automatic tool design procedure, based on the explicit FEM simulation of a stamping process, coupled to a geometrical tool compensation algorithm. The FEM simulation model has been first validated by comparing the experiments done at different levels of the process parameters. After the experimental validation of the FEM model, a compensation algorithm has been implemented for reducing the error between the simulated component and the designed one. The tooling setup is made of machined thermoset polyurethane (PUR) punch, die, and blank holder, for the deep drawing of an aluminum part. With respect to conventional steel dies, the plastic tools used in the test case are significantly more economic. The proposed procedure is iterative. It allows, already after the first iteration, to reduce the geometrical deviation between the actual stamped part and the designed geometry. This methodology represents one step toward the transformation of the investigated process from a prototyping technique into an industrial process for small and medium batch sizes.

Development of a Die Compensation Algorithm for Sheet Metal Stamping With Deformable Tools

The numerous sheet forming technologies that use rubber or flexible tools are generally based on one rigid (metallic) die or punch, in order to ensure a geometrical precision and repeatability of the parts. If, on the contrary, the complete tooling setup is based on deformable tools, the final part quality and geometry can be hardly predicted and only a prototypal production is generally possible. The aim of this paper is to present the development of an automatic tool design procedure, based on the explicit FEM simulation of a stamping process, coupled to a geometrical tool compensation algorithm. The implemented procedure is demonstrated with a tooling setup made of machined thermoset polyurethane punch, die and blankholder, for the production of an aluminum deep drawn part. With respect to conventional steel dies, the plastic tools used in the test case are significantly more economic than steel. The proposed procedure is able, within a limited number of iterations, or even after the first step, to reduce the geometrical deviation between the actual stamped geometry and the reference part. This methodology represents one step towards the transformation of the investigated process from a prototyping technique into an industrial process for small and medium batch sizes.

Axial Deformation of the Planetary Differential Micro-Displacement Mechanism with Finite Element Analysis

Based on the study of planetary differential roller screw, a planetary differential micro-displacement mechanism is designed for tool compensation. Axial stiffness is an important factor of over-all properties of planetary roller screw. The structure of planetary differential roller screw is similar to planetary roller screw. The axial stiffness was analyzed with Hertz contact theory and confirmed with the ANSYS. Finally, the theoretical values and simulation values were compared to verify the simplified model, and the error was analyzed. The results show that the relative error between simulation values and theoretical values are less than 5%. Therefore, the simplified model of the finite element is reasonable.