This paper presents a methodology and algorithms of optimizing and smoothing the tool orientation control for 5-axis sculptured surface machining. A searching method in the machining configuration space (C-space) is proposed to find the optimal tool orientation by considering the local gouging, rear gouging and global tool collision in machining. Based on the machined surface error analysis, a boundary search method is developed first to find a set of feasible tool orientations in the C-space to eliminate gouging and collision. By using the minimum cusp height as the objective function, we first determine the locally optimal tool orientation in the C-space to minimize the machined surface error. Considering the adjacent part geometry and the alternative feasible tool orientations in the C-space, tool orientations are then globally optimized and smoothed to minimize the dramatic change of tool orientation during machining. The developed method can be used to automate the planning and programming of tool path generation for high performance 5-axis sculptured surface machining. Computer implementation and examples are also provided in the paper.

Optimizing tool orientations for 5-axis machining by configuration-space search method

In theory, the 5-axis machining of sculptured surfaces offers many advantages over 3-axis machining, including faster material-removal rates, improved surface finish, and the elimination of hand finishing. In practice, 5-axis machining suffers from a number of drawbacks, which are mostly related to gouge avoidance. The paper describes research on algorithms for the generation of gouge-free, nonisoparametric 5-axis tool paths across composite surface patches. The approach includes (a) the tesselation of the parametric surfaces into triangles, (b) algorithms for the placement of a cylindrically shaped cutting tool onto the triangulated surface, and (c) interference detection and tool-position correction.

5-axis machining of sculptured surfaces with a flat-end cutter

This article presents a new format of tool path polynomial interpolation in 5-axis machining. The linear interpolation usually used produces tangency discontinuities along the tool path, sources of decelerations of the machine tool whereas polynomial interpolation reduces the appearance of such discontinuities. The new format involves a faster tool path and a better surface quality. However, it imposes a modification of the process so as to take the interpolation format and the inverse kinematics transformation (necessary to 5-axis machining) into account. This article deals with the geometrical problem of tool path calculation. Validation tests are detailed. They show that profits concern the reduction of machining time as well as the quality of the machined surfaces. Indeed, the trajectory continuity avoids the appearance of marks and facets.

A new format for 5-axis tool path computation, using Bspline curves

Recently, a large amount of new research related to numerical control (NC) tool path generation has appeared in the literature Unfortunately, finding information on a particular topic can be difficult Not only does path generation span several disciplines, but the material tends to vary both in content and focus In this paper, the literature is partitioned into categories and papers related to path generation classified according to the topics they cover This should be useful to those looking for references on specific topics as well as those seeking an introduction to the literature as a whole

https://www.cgl.uwaterloo.ca/smann/Papers/survey2.pdf

A classified bibliography of literature on NC milling path generation

5-Axis sculptured surface machining is simulated using discrete geometric models of the tool and workpiece to determine the tool contact area, and a discrete mechanistic model to estimate the cutting forces. An extended Z-buffer model represents the workpiece, while a discrete axial slice model represents the cutting tool. Determination of the contact area for a given tool move requires a swept envelope (SWE) of the tool path. The SWE is used to find the intersections of the tool envelope with Z-buffer elements (ZDVs) representing the workpiece. A 3-axis approximation of the 5-axis tool movement is used to simplify the calculations while maintaining a desired level of accuracy. The intersection of the SWE with each ZDV yields segments which are used to find the contact area between the cutter and the workpiece for a given tool path. The contact area is subsequently used with the discrete force model to calculate the vector cutting force acting on the tool.

Modeling of cutting geometry and forces for 5-axis sculptured surface machining

The numerically controlled (NC) machining of sculptured surfaces is an error-prone process often requiring several attempts before an error-free NC program is produced. A technique designed to move the NC proof process into software is described. The system outputs a color-coded graphics display of the machined surface that shows out-of-tolerance areas. To gain efficiency, surface curvature and cutting-tool size are used as inputs to a surface discretization algorithm, which guarantees that a user-defined level of simulation accuracy is achieved. The simulation time grows linearly in both desired accuracy and in the number of tool movements. In typical test cases, NC programs for complex automotive body panels were simulated and verified in CPU times that ranged between 5 and 30 minutes. >

R.B. Jerard

Papers

Methods for detecting errors in numerically controlled machining of sculptured surfaces