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Aluminum skin milling is a very challenging process due to the high quality requirements needed in the aeronautic and aerospace industries. Nowadays, on these markets, there are just two technological approaches able to face the manufacturing of this sort of wide thin blanks: chemical and mechanical milling by means of highly complex machines. Both solutions lead to a high investment requirement that affect directly on the application profitability on these industrial sectors. This paper presents a flexible machining system that allows milling skin shaped parts within required tolerances by means of an innovative universal holding fixture combined with an adaptive toolpath development. This flexible holding fixture can be adapted to the required shape and can hold uniformly the whole sheet surface. Besides, the solution includes an implementation that can adapt the machining toolpath by means of the skin thickness online measurement.

Gaps in composite structures are a risky factor in aeronautical assemblies. For mechanically joined composite components, the geometrical conformance of the part can be problematic due to undesired or unknown re-distribution of loads within a composite component, with these unknowns being potentially destructive. To prevent unnecessary preloading of a metallic structure, and the possibility of cracking and delamination in a composite structure, it is important to measure all gaps and then shim any gaps greater than 127 microns. A strategy to overcome the high relative tolerances for assemblies lies in the automated manufacturing of shims for the gaps previously predicted through the evaluation of their volumes via a simulation tool. This paper deals with the development of a special end-effector prototype to enable the shimming of gaps in composites structures using a pre-processed geometry.