Analysis and Optimal Design of Fixture Clamping Sequence

Abstract

Considering the great impacts of the application sequence of multiclamps on the workpiece machining accuracy, this paper analyzes and optimizes clamping sequence. A new methodology that takes into account the varying contact forces and friction force during clamping is presented for the first time. A new analysis model is established to capture the effect of clamping sequence on contact force distributions and workpiece machining accuracy. It reveals that the historical accumulation of clamping steps influences heavily the final distribution of contact forces in the workpiece-fixture system. Therefore, the present contact forces in each clamping step are solved incrementally in terms of contact forces of the precedent step by means of the principle of the total complementary energy. Furthermore, based on the fact that the variation of contact forces from one step to another results in different workpiece deformations and position, a novel design model is formulated to select optimally the clamping sequence in order to minimize the workpiece deformation and position errors. Workpieces of low stiffness and high stiffness are investigated separately in order to simplify the modeling of clamping sequence optimization. Some numerical tests are finally demonstrated to validate the proposed model and method. Computational results are discussed and compared with experimental results available in the reference.

A survey on smart automated computer-aided process planning (ACAPP) techniques

“…A fixture system is a set of clamps and locators aimed at removing the degrees of freedom, thereby restricting the part to that particular position [126,127]. The position and orientation of a workpiece is usually determined by locators, whereas clamps exert a clamping force in order to press the workpiece firmly against the locators [127,128]. Whilst jigs are used to locate and hold components as well as fixtures, they also guide the cutting tools and provide repeatability in the manufacturing of products [129].…”

“…Qin et al [128] developed a new methodology to analyse and optimise the clamping sequence by taking into account the varying of both contact and friction forces during clamping, which affects the degrees of freedom. A nonlinear mathematical programming problem was solved in order to evaluate the errors of varying contact forces and workpiece position in each clamping step.…”

A non-uniform allowance allocation method based on interim state stiffness of machining features for NC programming of structural parts

“…The experimental results show that high material removal rate and machining accuracy can be obtained by using this special fixture during the machining process. Considering the influence of clamping sequence on machining accuracy, Qin et al [3] established a model for analyzing and optimizing clamping sequence of parts. This method can reduce the machining deformation and positioning error by establishing the relation between the distribution of contact force and the machining accuracy of the parts, and finally improve the machining rigidity of the system.…”

Model Optimasi Fixturing Benda-kerja dengan Prinsip 3-2-1 Klem Tunggal

“…Qin et al [8] melakukan analisis dan optimasi skema penempatan penetap yang menghasilkan prinsip dan kriteria desain optimal. Qin et al [9] melakukan analisis dan optimasi urutan pencekaman yang akan meminimumkan deformasi dan kesalahan posisi bendakerja dengan fungsi pembatas geometri dan deviasi. Krishnakumar dan Melkote [10] serta Kaya [11] melakukan optimasi tata-letak lokator untuk me-nentukan koordinat lokator dan klem agar pergeseran yang terjadi minimum.…”