Concept design of a 5-axis portable milling machine for the in-situ processing of large pieces

For conventional machine tools the work piece is placed inside the structure and therefore its overall dimensions determine the size of the workspace and with it also the general size of the complete system, which leads to extreme disproportions between theoretically appropriate and actually needed system size. In large pieces this results in even larger machines presenting technical and practical issues well known and described in the state-of-the-art. An alternative to solve this issue is to get rid of the dogma "work piece inside the machine" and replace it by the principle "small machines on large work pieces" [1][2]. This paper presents and discusses a new paradigm of portability and proposes the basic design of an advanced portable machine for in-situ and on-the-part milling of large components. More specifically, the machine shall be able to machine features larger than itself without continuity issues and automatically by means of an array of sensors and built-i n CAM reprocessing capabilities, in close contact with the CAD file of the piece. For enhanced functionality, the machine targets usual engineering materials (steel, aluminium and composites) and processes (drilling and milling) with mid-to-high removal rates with a fully-flexible 5-axis configuration. Said machine will become the backbone of a set of R&D efforts in the field of miniature and portable machines with a view to developing sound solutions for the limitations of portable machines in terms of part and feature precision, machine clamping on the part and process capabilities with limited machine sizes.