ANALYSIS OF MACHINING CONFIGURATIONS WITH BALL-END MILLS IN ORDER TO FINISH PARTS MADE BY EBM AND COMPARISON WITH NUMERICAL MODEL

During the last 25 years additive manufacturing technologies have continued to grow.
In the future, we can expect a continuation of this rapid expansion not only to make prototypes but also and mainly to produce finished parts in small series.
The EBM (Electron Beam Melting) method is one of those technologies. It allows the manufacturing of fully dense parts layer by layer from a non-magnetic metal powder. With rapid prototyping process, the part was built with material like polymers and it was just a visualization step in the production process. The EBM isn't only a visualization step in the production cycle. It allows the fabrication of parts with good mechanical properties directly by a CAD model.
In the future this process will be more used for the small series production. As an example, it's now possible to produce prostheses (jaw, hip, thumbs,...) adapted to the morphology of the patients. But a finishing operation is still missing.
Until the present day there is no quality standard for parts produced by EBM. This process has some limitations. It leads to a pore surface quality. So post processing operations are required in order to obtain good characteristics.
In this study, the finishing of parts made by EBM will be performed by multiaxis milling. This technology is typically used to produce free-form surfaces. The geometry of the tool that is traditionally used for this type of operation is ball nose.
The multiaxis milling offers the possibility of inclination of the tool according to two angles. That results in a variety of geometric configurations. But therefore it is necessary to compute the most appropriate settings.
Furthermore, a software that had been developed by the Machine Design and Production Engineering Department of the Faculty of Engineering of the University of Mons allows notably to determine cutting forces. There are 3 aspects coupled in this software: a dynamic model, a geometric model and an effort model.
This study will be conducted in first time on Ck45 steel with a ball-end mill. Different configurations will be tested by varying the angle of inclination perpendicular to the advance. A measurement of the cutting forces depending on the tilt angle will be carried out to determine the optimum angle of inclination for the multiaxis machining.
In second step, we will compare the cutting forces measured experimentally with those obtained by the Dystamill software.