Structural Analysis Of Hollow-center Tap

Hollow-center taps are mainly used in processing large diameter screws in heavy machinery such as turbomachine,electric,generator,reactor...etc.In actually production process,problems such as claws fracture,low screw thread accuracy are frequently occurred because of that hollow-center taps has a special cutting part.One of the most important factors is the unreasonable structure design for hollow-center taps.For hollow-center taps,the two key factors which affecting the strength of hollow-center taps are its diameter of cavity and claws number.In order to ensure effective chip capacity and precision,larger cavity diameter and more claws should be used,but this will make the cutting claw become thin and make it easy to break.For how to determine these two parameters,there is no detailed calculation method in existing literature.Most domestic manufacturers use empirical data or model the foreign products.In order to understand the relationship between these two parameters,we need to optimize these two parameters of hollow-center taps.In this paper,firstly,cutting force in tapping process was calculated by empirical torque formula under a certain geometric parameters.The deformation and the largest stress equation were derived by the analysis of the cutting claws's deforming under the cutting force,and then used some methods to establish the objective function for optimization by screw accuracy and tap strength demands.Calculate the max-diameter for hold-chip cavity and max-deflection of claw and maximum stress of dangerous section under specific number of claws by optimizing compiler.Then, based on the optimization results, establish the geometric model using Solid-works,and import this model to ansys workbench.In this article we distribute cutting force matching to its actually cutting areas, because different claws have different actually loads. Moreover ,due to the limitations of ansys workbench on applying loads, in this article we convert cutting force for each claw.Finally ,this paper verified the accuracy of optimization theory through the simulations by ansys workbench in this article .In the later part of this paper ,we effectively reduce the maximum-stress of dangerous sections,with the help of optimal design of other parameters of hollow-center taps, and this also prolongs the tool's lifetime .Moreover ,the methods used in this article have some guidance on hollow-center taps design.It is obvious that with a reasonable cutting force calculation and loading manner, optimizing the structure of hollow-center taps by using the method mentioned in this article is reasonable and feasible.