Machining of curved geometries with constant engagement tool paths

Abstract

End milling of the curved surfaces is characterized by significant amount of engagement variation along the tool path which results in deflection-induced surface error on the machined components. Feed rate regulation cannot be used in this case to minimize the surface errors as it necessitates continuous change in feed rate along the tool path which deteriorates surface finish and lowers productivity. Another approach in the form of tool path modification scheme was also proposed in the literature to minimize engagement variation at corners of a pocket. This approach has been effective in reducing fluctuations of engagement at corners and cannot be applied directly in machining of curved geometries where engagement variation is continuous along the entire tool path. Keeping these limitations in focus, a new methodology is proposed in this article to minimize surface error variation that modifies machining strategy for the curved components. The strategy proposes machining of the curved components into two different stages: first, generating the modified semi-finishing geometry using algorithm proposed in this article and then producing the desired geometry using conventional contour parallel tool path. The methodology generates the modified semi-finishing geometry such that the engagement offered is constant when a finishing pass is made. The effectiveness of the proposed methodology has been verified by performing computational studies and machining experiments on typical curved geometries. It is observed that the proposed methodology is quite effective in minimizing the variation in the surface error on the machined components.

Determination of force coefficient based on instantaneous forces and linear mechanistic model in ball end milling

“…Shear, and edge force coefficients were determined using the experimental instantaneous cutting forces in tangential, radial, and axial directions as shown in Table 2. A MATLAB code was written considering the local geometries of the cutter to obtain the force coefficients using the equation (27). Calculated values of K ts , K rs , and K as have been plotted against feeds for a p in the range of 0.2-1.8 mm as shown in Figure 5(a) to (c).…”

“…Based on the true tooth trajectory, Sai et al 24 had analytically determined uncut chip thickness and CWE and further used it in the mechanistic model to calculate the cutting forces. CWE region, cutting-edge trajectory, and cutter path [25][26][27] are critical factors that influence the determination of force coefficients in BMP. The BMP is heavily influenced by various parameters such as cutting forces, heat generation, power, etc.…”

The fast constant engagement offsetting method for generating milling tool paths

“…Phrased briefly, controlling the feed rate alone is not adequate in this process. Thus, in order to reach an efficient solution, modifications in the shape of the tool path are necessary [27].…”

A hybrid fabrication approach and profile error compensation for silicon aspheric optics

“…To overcome this, systematic approach with optimised lapping parameters and gradually increasing lapping and grinding speed can be helpful to achieve the accuracies with less surface and subsurface damage. [15][16][17] Rapid tool wear is another critical issue related to machining of brittle materials. Tool wear not only affects the profile accuracies but also increases the cost and processing time.…”