Study On The Techniques Of Automatic Customized Shoe-Last Based On 3D Foot Shapes

Nowadays, production of customized shoes is becoming a key point in market competition to meet the needs from all kinds of consumers. Requirements on shoe last design in accordance with foot shape and a special system combining foot measurement with shoe last CAD/CAM become more and more urgent.This dissertation is focused on the automatic manufacturing of customized shoe-lasts based on 3D foot shapes.The data of point clouds of the preprocessed foot data are modified by using the improved cubic smoothing spline interpolation method together with the least square patch fittings. The shoe-last point data are preprocessed by means of a probe compensation and the discretization of the points in U-direction,and the data are then smoothed using the wavelet transform.A standard shoe-last database is established with an open structure, and a method for an automatic extraction of foot parameters is proposed.The parameters are then employed to match the standard shoe-last according to the matching principles.A segment-based foot-last mapping modeling method based on generative formula is proposed. Regular data clouds can be classified into several feature segments, and an inference engine is used to calculate the deformation value of the feature points. A length fator is calculated from the foot length and the standard shoe-last, and a width factor is calculated with the footprint-lastprint width to obtain the scale amount of all secondary points. Local deformation amount is obtained by constructing two allowable deviation curves to modify the actual curves in the permitted error range.After fitting to the U-direction NURBS curves, scaling and deformation of shoe last according to the standard shoe last are performed to the foot shape with an algorithm. An energy optimization-based method is proposed to modify the control points and the weight factors to fit the standard shoe last adaptively, realizing thus a digital customized shoe last. All the points are realigned in V-direction, and the control points in V-direction are once again calculated to model the shoe-last with NURBS curves. The tool path of the shoe-last is obtained with an equidistant surface method and a simulation is performed with Unigraphic to verify the tool path.