Sets of lines and cutting out polyhedral objects

AbstractWe study algorithmic questions related to cutting polyhedral shapes with a hot wire cutter. Such cutters are popular manufacturing tools for cutting expanded polystyrene (styrofoam) with a thin, moving heated wire. In particular, we study the question of polyhedral-wise continuity: Can a given object be cut out without disconnecting and then reattaching the wire? In an abstract setting this question translates to properties of sets of lines and segments and therefore becomes suitable for computational geometry techniques. On the combinatorial and algorithmic levels the results and methods are related to two problems: (1) given a set F={f1,…,fk} of polygons and a polygon f, decide if there is a subset of lines in the set of lines not stabbing F that cover f; (2) construct the connectivity graph for free movements of lines that maintain contact with the polyhedral shape. Problem (1) is solved with the dual projection and arrangements of convex and concave x-monotone curves. Problem (2) can be solved with a combination of the skewed projections [6] and hyperbola arrangements proposed by McKenna and O'Rourke [11]. We provide an O(n5) algorithm for constructing a cutting path, if it exists. The complexity of the algorithm is determined by the O(n4) size of the connectivity graph and the cost of solving (2)

Material Removal Optimization Strategy of 3D Block Cutting Based on Geometric Computation Method

During the material removal stage in stone rough processing, milling type has been widely explored, which, however, may cause time and material consumption, as well as substantial stress for the environment. To improve the material removal rate and waste reuse rate in the rough processing stage for three-dimensional stone products with a special shape, in this paper, circular saw disc cutting is explored to cut a convex polyhedron out of a blank box, which approaches a target product. Unlike milling optimization, this problem cannot be well solved by mathematical methods, which have to be solved by geometrical methods instead. An automatic block cutting strategy is proposed intuitively by considering a series of geometrical optimization approaches for the first time. To obtain a big removal block, constructing cutting planes based on convex vertices is uniquely proposed. Specifically, the removal vertices (the maximum thickness of material removal) are searched based on the octree algorithm, and the cutting plane is constructed based on this thickness to guarantee a relatively big removal block. Moreover, to minimize the cutting time, the geometrical characteristics of the intersecting convex polygon of the cutting plane with the convex polyhedron are analyzed, accompanied by the constraints of the guillotine cutting mode. The optimization algorithm determining the cutting path is presented with a feed direction accompanied by the shortest cutting stroke, which confirms the shortest cutting time. From the big removal block and shortest cutting time, the suboptimal solution of the average material removal rate (the ratio of material removal volume to cutting time) is generated. Finally, the simulation is carried out on a blank box to approach a bounding sphere both on MATLAB and the Vericut platform. In this case study, for the removal of 85% of material with 19 cuts, the proposed cutting strategy achieves five times higher the average material removal rate than that of one higher milling capacity case

Modelling, Monitoring, Control and Optimization for Complex Industrial Processes

This reprint includes 22 research papers and an editorial, collected from the Special Issue "Modelling, Monitoring, Control and Optimization for Complex Industrial Processes", highlighting recent research advances and emerging research directions in complex industrial processes. This reprint aims to promote the research field and benefit the readers from both academic communities and industrial sectors