T-Spline Surface Toolpath Generation Using Watershed-Based Feature Recognition

Yazui Liu,Gang Zhao,Pengfei Han

doi:10.3390/app10196790

Abstract

The freeform surface is treated as a single machining region for most traditional toolpath generation algorithms. However, due to the complexity of a freeform surface, it is impossible to produce a high-quality surface using one unique machining process. Hence, region-based methods are widely investigated for freeform surface machining to achieve an optimized toolpath. The Non-Uniform Rational B-spline Surface (NURBS) represented freeform surface is not suitable for region-based toolpath generation because of the surface gaps caused by NURBS trimming and merging operations. To solve the limitation of the NURBS, T-spline is proposed with the advantages of being gap-free, having less control points, and local refinement, which is an ideal tool for region-based toolpath generation. Thus, T-spline is introduced to represent a freeform surface for its toolpath generation in the paper. A region-based toolpath generation method for the T-spline surface is proposed based on watershed technology. Firstly, watershed-based feature recognition is presented to divide the T-spline surface into a set of sub-regions. Secondly, the concept of a PolyBoundingBox that consists of a set of minimum bounding boxes is proposed to describe the sub-regions, and Manufacturing-Suitable Regions are constructed with the help of T-spline local refinement and the PolyBoundingBox. In the end, an optimized multi-rectangles toolpath generation algorithm is applied for sub-regions. The proposed method is tested using three synthetic T-spline surfaces, and the comparison results show the advantage in toolpath length and toolpath reversing number.

Highlights

Freeform surfaces play a critical role in the field of shipbuilding, automotive, and aerospace.Toolpath generation is the fundamental task for freeform surface manufacturing
The proposed method is developed in the C++ programming language, which consists of watershed-based feature recognition, T-spline local refinement, and an optimized multi-rectangle toolpath generation algorithm
T-spline is introduced describe freeform region-based generation method for a T-spline surface is presentedto based on watershed surface, with to segment a freeform surface a setmost of gap-free technology in the thiscapability report

Summary

Introduction

Freeform surfaces play a critical role in the field of shipbuilding, automotive, and aerospace. Toolpath generation is the fundamental task for freeform surface manufacturing. The ideal toolpath should be generated uniformly across the whole surface, and the scallop height should be maintained below the specified value. From the geometric point of view, the freeform surface is generally designed feature-by-feature to satisfy the modeling functionality, and different features usually have diverse manufacturing properties. It is difficult to achieve a consistent scallop using single toolpath.

Methods

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Discussion

Conclusion