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Optimized grid structures for the characteristic diagram based estimation of thermo-elastic tool center point displacements in machine tools

Putz M., Ihlenfeldt S., Naumann C., Glänzel J.

Journal of Machine Engineering

2017

Vol. 17, No. 3

36--50

It is a well-known problem of milling machines, that waste heat from motors, friction effects on guides and also the milling process itself greatly affect the positioning accuracy and thus the production quality. An economic and energy-efficient method of correcting this thermo-elastic positioning error is to gather sensor data from the machine tool and the process and to use that information to predict and correct the resulting tool center point displacement using high dimensional characteristic diagrams. The size of these characteristic diagrams depends on the number of input variables (sensors) and the fineness of the discretization of the grid. While the number of sensors can usually not be reduced without affecting the quality of the prediction, it is often possible to minimize the size of characteristic diagrams through the use of adaptive grid refinement. This ensures that the finest grid sections correspond with the load cases that have the largest local gradients. Through such adaptive refinement, it is possible to reduce storage capacity and computation time without significant loss of precision. The aim of this article is to examine, test and compare different methods of adaptive grid refinement. For this, simulation data from a machine tool is used.

Simulation aided design of intelligent machine tool components

Mohring H. C., Wiederkehr P., Leopold M., Nguyen L. T., Hense R., Siebrecht T.

Journal of Machine Engineering

2016

Vol. 16, No. 3

5--33

By integrating sensors and actuators, intelligent machine tool components can be realized, which allow the monitoring of machining processes and machine tool states and an active influencing of process conditions. In the design and layout of these intelligent machine tool components, their mechanical structure and the functional performance of the sensor and actuator sub-systems have to be optimized. As an example, a sensor and actuator integrated fixture system for clamping large but sensitive aerospace structural parts is presented here. In order to investigate the major influences of design approaches on the behaviour of the workpiece and fixture, especially with respect to vibrations and process stability during milling, multiple test rigs and prototypes for basic analyses and machining tests were developed and realized. Experimental and Finite Element Analysis (FEA) results are presented and discussed. Process simulations were conducted taking the dynamic behaviour of the clamped workpiece at different processing steps into account. This simulation can be used for predicting the limits of the process stability. An approach of sensor and actuator integration is described and test results are shown. The paper introduces a principle design and layout methodology for similar intelligent machine tool components.

Structural analysis of shearing mirror assembly in a lateral double-shearing interferometer

Li A., Luan Z., Jiang X., Bian Y., Wang L., Liu L.

Optica Applicata

2011

Vol. 41, nr 3

701--715

By the finite element analysis method, the deformation and stress of the double-shearing mirror assembly is studied to validate the feasibility of the opto-mechanical structure. The side axial deformations (within A400 mm) of the upper semicircular mirror and the lower one are both up to micrometer order along the Y-direction under gravitational action. The equivalent stresses of two semicircular mirrors are more concentrated in the contact areas, but far less than the admissible stress of K9 material. The axial deformations of double-shearing mirror surfaces induced by the temperature rise are very serious, which are the major error sources for the measurement accuracy. The experimental results further validate the analysis conclusions available and show the opto-mechanical design to be reasonable.