Visibility from a Slice File for Rapid CNC Machining

A methodology for using CNC machining as a rapid prototyping process is being developed. The method involves cutting complex parts using layer-based machining operations from a plurality of orientations about one axis of rotation. A critical step is to determine the number of and location of those orientations. This paper presents an approach to mapping the visibility of a model about an axis of rotation using a set of model slices taken orthogonal to the axis of rotation

Orthogonal polygon reconstruction from stabbing information

AbstractReconstruction of polygons from visibility information is known to be a difficult problem in general. In this paper, we consider a special case: reconstruction of orthogonal polygons from horizontal and vertical visibility information and show that this reconstruction can be performed in O(nlogn) time

Determining Setup Orientations From the Visibility of Slice Geometry for Rapid Computer Numerically Controlled Machining

A method for rapid computer numerically controlled (CNC) machining is being developed in an effort to automatically create functional prototypes and parts in a wide array of materials. The method uses a plurality of simple two-and-a-half-dimensional (21/2-D) toolpaths from various orientations about an axis of rotation in order to machine the entire surface of a part without refixturing. It is our goal to automatically create these toolpaths for machining and eliminate the complex planning traditionally associated with CNC machining. In this paper, we consider a problem that arises in automating this process - visibility to the surface of a model that is rotated about a fourth axis. Our approach involves slicing the computer-aided design (CAD) model orthogonal to the axis of rotation. The slice geometry is used to calculate two-dimensional visibility maps for the set of polygons on each slice plane. The visibility data provides critical information for determining the minimum number and orientation of 21/2-D toolpaths required to machine the entire surface of a part

Stabbing information of a simple polygon

Article dans revue scientifique avec comité de lecture.The purpose of this paper is to investigate a new combinatorial object describing the structure of a simple polygon and compare it to other well-known objects such as the internal and external visibility graphs, the convex hull and the order type of the vertex set. We call the new object the stabbing information. In fact, we define three variations of the stabbing information, strong, weak and labelled, and explore the relationships among them. The main result of the paper is that strong stabbing information is sufficient to recover the convex hull, the internal and external visibility graphs and to determine which vertices are reflex and it is not sufficient to recover the order type of the vertex set. We also show that the labelled stabbing information is equivalent to the order type. We give algorithms for computing each of these new structures