The CAM as the centre of gravity of the five-axis high speed milling of complex parts

The use of multi-axis high-speed milling has increased in different industrial sectors such as automotive, aeronautical, and the manufacturing of complex moulds. This trend can be observed at the latest technical fairs and the catalogues of the main machine tool manufacturers. Furthermore, for machining impossible shapes, multi-axis machining introduces two main advantages. First it gives the option of performing all operations in only one set-up of the raw block, which can be a prismatic block or a near-to-net shape form. Second it offers the capability of setting the cutting speed, depth of cut and feed to optimize tool life and part quality.

However, multi-axis milling is a very complex process that requires special care in the CNC program preparation in the CAM stage, which is critical for a successful process. Thus, the use of a virtual machining simulation utility is highly recommended. Collisions, over-cuts, interferences and dangerous machine movements can be predicted and avoided. On the other hand, continuous variation of the tool can be used to optimize cutting parameters such as cutting forces. Final result is the minimization of tool deflection due to the cutting forces and, in this way, the precision and roughness of finished parts are improved.

In this paper a reliable method for multi-axis HSM is presented. This methodology is based on two aspects. First a cutting force estimation in order to get minimum cutting force tool-paths. Second a complete virtual simulation to ensure a collision-free tool-path. A final objective is to generate reliable CNC programs. In this manner, the CAM becomes the centre of gravity of the machining planning procedure.

The methodology has been applied to the machining of two plastic moulds in hardened steel (32 HRC), a 7075-T6 aluminium honeycomb part for aeronautical purposes and a 65 HRC AISI 1.2379 part. Times, tolerances and surface roughness have been measured to check the success of the purposed methodology.