Light Controlled Factory
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Research Theme 2

Model based and physical measurement methods for establishing the uncertainty of the spatial fidelity of large, complex tools and parts due to gravitational effects and thermal gradients (Year 0-3.3)

AIT tools and jigs for large complex products can typically be from 5 to 30 meters in length and up to 10 meters in height. In uncontrolled factories there can be thermal gradients of 3-5°C and the temperature variation can reach 15°C over a 24 hr cycle. The effect of gravitational deflection and temperature variation on large parts and tooling structures can be the dominant dimensional uncertainty source that is larger than the assembly tolerances (c. 200 μm). The WPs will be as follows:

WP2.1 Hybrid – model based and physical measurement – technique for structural fidelity (Mullineux, Maropoulos).

A digital assembly model will be constructed, representing; (i) major structural elements of the assembly environment and major parts in FEA in order to model and predict the shape distortion and the resulting 6 DOF position of assembly features

(ii) the tolerance stack-up of the assembly using advanced tolerance analysis techniques. A novel, hybrid -computational model based and physical measurement – methodology will be developed and evaluated to manage the uncertainty in the overall structural compliance of an AIT environment. The method will involve fusing the model based predictions with actual measurement data, at selected points and time intervals. By fusing model data with measurements and then remodelling, the research will generate a new class of computational tools for the real-time update of digital models using measurement data, allowing enhanced process control.

WP 2.2 Strategy for measurement data acquisition and fusion with model data. (Maropoulos, Mullineux, Robson, Boehm).

At critical stages of the assembly in terms of tolerance stack-up, dimensional measurements will be made to establish the 6 DOF position of key features and thermal measurement data will be retrieved from the AIT environment using structure based sensors supplemented by novel acoustic tomography techniques in co-operation with NPL and WP3. The measurements will then be incorporated into the model, replacing the uncertainty of the predicted compliance and tolerance stackup (from 1 to 5 mm) with the measurement uncertainty (50 to 200 μm) of the as-assembled structures.

This order of magnitude reduction in the uncertainty of the assembly will result in; (i) enhanced assembly process capability and adaptive assembly, even for one-off products, and (ii) being able to demonstrate assembly conformance to design specifications for the purpose of product certification.