Automatic compensating cleanup operation

Journal ArticleToday's part geometries are becoming ever more complex and require more accurate tool path to manufacture. Machining process efficiency is also a major consideration for designers as well as manufacturing engineers. Although the current advanced CAD/CAM systems have greatly improved the efficiency and accuracy of machining with the introduction of Numerically Controlled (NC) machining, excessive material may still be left on the finished part due to machining constraints, including the inaccessibility of the designed part geometry with respect the cutter, machine motion constraints like ramp angles, specific cutting patterns, etc. Polishing operations such as grinding and hand finishing are quite time consuming and expensive and may damage the surface of the part or introduce inaccuracies because of human errors. Although most of the existing machining approaches attempt to reduce such excessive restmaterials by modifying NC tool paths, none of them is satisfactory. They can be time consuming, error prone, computationally intensive, too complicated to implement, and limited to certain problem domains. A compensating cleanup tool path will be developed in this research to automatically remove these excessive material from the finish part. This method greatly reduces the burden of hand finishing and polishing and also reduces the error and complexities introduced in manually generating cleanup tool paths in the shop floor. More important, the tool path generated by this method will reduce the machining time and increase tool life compared with optimized tool path which left no excessive material behind

The flow approach to swept volume

In this thesis, a method for representing swept volume based on the sweep differential equation and sweep vector field flow is developed. This method can be used to determine the boundary representation of a swept volume generated by any polygonal object undergoing a general smooth 2-D sweep. For any given sweep and object, a. set of candidate boundary points is computed using a selection criterion based on vector field behavior. The set of candidate boundary points is then trimmed in order to obtain the true boundary of the swept volume. This trimming procedure is based on some simple topological principles and it utilizes the concept of extended sweep. This method is more general and efficient than existing approaches (e. g. it can readily deal with the cases in which the swept volume area. has holes ) and can easily be extended to 3-D sweeps; the 3-D extension is discussed but only briefly. Several examples are given to illustrate the implementation of the prototype software for 2-D sweeps which has been developed in conjunction with this research

Reaction forces on a milling tool during three-axis milling

This thesis discusses a graphical numerically controlled (NC) milling simulation. Graphical simulations give a better feel for what happens during a complicated process, such as NC milling, than does numerical output from a mathematical model. NC milling simulations can be used to verify tool paths, detect collisions, and check the material removal rate, which can be related to force feedback on the milling tool. A graphical simulation should make calculations and update displays as quickly as possible, while still maintaining a reasonable level of accuracy. This thesis presents a real time NC milling simulation technique that incorporates a cutting force model to calculate forces generated between the milling tool and the workpiece. This information can be used to determine if a piece of the machinery could fail due to driving (feeding) the milling tool too rapidly, creating too large a force on the tool shaft or flutes

Automatic tool path generation for numerically controlled machining of sculptured surfaces

This dissertation presents four new tool path generation approaches for numerically controlled machining of sculptured surfaces: TRI\sb-XYINDEX, FINISH, FIVEX\sb-INDEX, FIX\sb-AXIS\sb-INDEX. All of the above systems index the tool across the object surface in the Cartesian space so that evenly distributed tool paths are accomplished. TRI\sb-XYINDEX is a three-axis tool path generation system which uses a surface triangle set (STS) representation of the surface for tool position calculations. Surface edges are detected with local searching algorithms. Quick tool positioning is achieved by selecting candidate elements of polygons. Test results show that TRI\sb-XYINDEX is more efficient when machining surfaces which are relatively flat while the discrete point approach is faster for highly curved surfaces. FINISH was developed for generating three-axis ball-end tool paths for local surface finishing. It was based on the SPS. Given a surface with excess material represented by a set of discrete points, FINISH automatically identifies the undercut areas. Results show that FINISH provides significant improvements in machining efficiency. FIVEX\sb-INDEX is developed for generating five-axis flat-end tool paths. It uses an STS approximation. Contact points on the surface are derived from edge lists obtained from the intersections of vertical cutting planes with the polygon set. The distances between adjacent end points set an initial step-forward increment between surface contact points. To verify tool movements, some intermediate tool positions are interpolated. The key features of FIVEX\sb-INDEX are: (1) a polygon set representing an object which may be composed of multiple surfaces; (2) Surface contact point generation by cutting plane intersection; (3) simple tool incrementing and positioning algorithms; (4) minimal user interaction; (5) user controlled accuracy of resulting tool paths. FIX\sb-AXIS\sb-INDEX is a subsystem of FIVEX\sb-INDEX, generating tool paths for a tool with fixed orientations. Surface contact points are generated similar to FIVEX\sb-INDEX while tool positions are corrected with the highest point technique along the tool axis direction. Linear fitting is applied to output tool positions. FIX\sb-AXIS\sb-INDEX is preferred for machining surfaces curved in one direction, such as ruled surfaces. Test results show that FIX\sb-AXIS\sb-INDEX can serve as a three-axis tool path generation system but a five-axis machine is required to do it. (Abstract shortened by UMI.)

Time Distance: A Novel Collision Prediction and Path Planning Method

Motion planning is an active field of research in robot navigation and autonomous driving. There are plenty of classical and heuristic motion planning methods applicable to mobile robots and ground vehicles. This paper is dedicated to introducing a novel method for collision prediction and path planning. The method is called Time Distance (TD), and its basis returns to the swept volume idea. However, there are considerable differences between the TD method and existing methods associated with the swept volume concept. In this method, time is obtained as a dependent variable in TD functions. TD functions are functions of location, velocity, and geometry of objects, determining the TD of objects with respect to any location. Known as a relative concept, TD is defined as the time interval that must be spent in order for an object to reach a certain location. It is firstly defined for the one-dimensional case and then generalized to 2D space. The collision prediction algorithm consists of obtaining the TD of different points of an object (the vehicle) with respect to all objects of the environment using an explicit function which is a function of TD functions. The path planning algorithm uses TD functions and two other functions called Z-Infinity and Route Function to create the collision-free path in a dynamic environment. Both the collision prediction and the path planning algorithms are evaluated in simulations. Comparisons indicate the capability of the method to generate length optimal paths as the most effective methods do

Sweeping of three-dimensional objects

Evaluating the volume swept out by a three-dimensional (3D) object as it moves along an arbitrary path is of interest to many areas of CAD and CAM, such as mechanism design and robot path planning. This paper shows how envelope theory from differential geometry can be used to find the volumes swept out by the individual surfaces of a solid body, and how computer algebra methods may be of use to perform the computations involved. Finally, a new algorithm is presented which shows how the results of sweeping the individual surfaces of a solid body can be combined to form a new 3D model of the swept volume. This algorithm has strong resemblance to hidden line algorithms, but works in one dimension higher

Engineering data compendium. Human perception and performance, volume 3

The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design of military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by system designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is Volume 3, containing sections on Human Language Processing, Operator Motion Control, Effects of Environmental Stressors, Display Interfaces, and Control Interfaces (Real/Virtual)

A STUDY OF THE APPLICATION OF AUGMENTED REALITY TECHNOLOGY ON 3-AXIS CNC IN SITU MACHINING SIMULATION

Ph.DDOCTOR OF PHILOSOPH