A Method for Predicting and Compensating Tool Allowance Errors in Micro Milling of Freeform Surfaces

Abstract

The invention discloses a method for predicting and compensating cutter back-off error in free-form surface micro milling. In consideration of smaller deformation of a machining cutter for the free-form surface micro milling, a hypothesis that normal vectors of an ideal cutter location point and a real cutter location point are consistent in a micro-region to which the ideal and real cutter location points belong is put forward; in consideration of a feedback effect of deformation of a micro-diameter ball-end cutter on a cutting force, the cutter back-off error in a cutting balance state is solved by adopting an iterative algorithm; and the cutter back-off error is taken as the predicting value of the cutter back-off error, so that the predicting result is more accurate. Furthermore, the total compensation amount of the cutter back-off error is calculated through iterative computation, and the cutter back-off is compensated directly; the compensation amount is the smallest; the compensation orientation is explicit; the physical significance is clear; and the machining precision is high.

Description

technical field [0001] The invention belongs to the technical field of micro-milling, and more specifically relates to a method for predicting and compensating tool-off errors in micro-milling of free-form surfaces. Background technique [0002] In the process of machining free-form surface, the existence of let-off error leads to the reduction of its shape accuracy, which in turn affects the performance of the workpiece. Accurate prediction of the tool clearance error can provide a basis for the formulation of process parameters. By selecting more reasonable parameters to ensure that the shape error of the workpiece is within the tolerance range; researching the compensation of the tool clearance error can reduce tool deformation by means of compensation Influence on shape accuracy, improve workpiece quality. [0003] In the field of micro-milling of free-form surfaces, the tool diameters used are usually small, and generally belong to the category of "slender" tools, so t...

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Problems solved by technology

First of all, unlike the ordinary milling of free-form surface, the tool used in the micro-milling of free-form surface is a micro-diameter ball-end cutter, and it is difficult to measure the radial stiffness of the tool by the "hanging method" of the ordinary ball-end cutter; secondly, in the free-form surface In the relevant research on the prediction of tool-off error in ordinary milling of curved surfaces, the cutting force at the ideal tool position is generally used to calculate the tool-off error directly, without considering the feedback effect of tool deformation on the cutting force during the machining process, which affects the prediction of tool-off error. Accuracy; again, in the related research on the compensation of tool clearance error in ordinary milling of free-form surface, generally, the ideal tool position point is directly offset by a tool deformation amount in the opposite direction of tool deformation to compensate for tool clearance error. Failure to perform iterative calculation will lead to Small compensation amount affects machining accuracy

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