No abstract

Milling is today the most effective, productive and flexiblemanufacturing method for machining complicated or sculptured surfaces. Ball-end tools are used for machining 3D freeform surfaces for dies, moulds, and various parts, such as aerospace components, etc. Milling data, such as surface topomorphy, surface roughness, non-deformed chip dimensions, cutting force components and dynamic cutting behaviour, are very helpful, especially if they can be accurately produced by means of a simulation program. This paper presents a novel simulation model, the so-called MSN-Milling Software Needle program, which is able to determine the surface produced and the resulting surface roughness, for ball-end milling. The model simulates precisely the tool kinematics and considers the effect of the cutting geometry on the resulting roughness. The accuracy of the simulation model has been thoroughly verified, with the aid of a wide variety of cutting experiments. Many roughness measurements were carried out on workpieces, which were cut using a 5-axis machining centre. The calculated roughness levels were found to be in agreement with the experimental ones. The proposed model has proved to be suitable for determining optimal cutting conditions, when finishing complex surfaces. The software can be easily integrated into various CAD-CAM systems.

No abstract

No abstract

Gear hobbing is an efficient method to manufacture high quality and performance toothed wheels, although it is associated with complicated process kinematics, chip formation and tool wear mechanisms. The variant cutting contribution of each hob tooth to the gear gaps formation might lead to an uneven wear distribution on the successive cutting teeth and to an overall poor tool utilization. To study quantitatively the tool wear progress in gear hobbing, experimental-analytical methods have been established. Gear hobbing experiments and sophisticated numerical models are used to simulate the cutting process and to correlate the undeformed chip geometry and other process parameters to the expected tool wear. Herewith the wear development on the individual hob teeth can be predicted and the cutting process optimized, among others, through appropriate tool tangential shifts, in order to obtain a uniform wear distribution on the hob teeth. To determine the constants of the equations used in the tool wear calculations, fly hobbing experiments were conducted. Hereby, it was necessary to modify the fly hobbing kinematics, applying instead of a continuous tangential feed, a continuous axial one. The experimental data with uncoated and coated high speed steel (HSS) tools were evaluated, and correlated to analytical ones, elaborated with the aid of the numerical simulation of gear hobbing. By means of the procedures described in this paper, tool wear prediction as well as the optimization of various magnitudes, as the hob tangential shift parameters can be carried out.