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Teaser, summary, work performed and final results

Periodic Reporting for period 1 - ECSASDPE (European and Chinese Platform for Stacked Aero-Structure Drilling Process and Equipment)

Teaser

Weight reduction and cost savings have driven composites research towards a number of recent high profile achievements. The increased use of anisotropic AL/CFRP/Ti stacks in aircraft structures has in turn created enormous challenges for the industry due to the difficulties...

Summary

Weight reduction and cost savings have driven composites research towards a number of recent high profile achievements. The increased use of anisotropic AL/CFRP/Ti stacks in aircraft structures has in turn created enormous challenges for the industry due to the difficulties that arise from drilling these heterogeneous stack materials. The project “European and Chinese Platform for Stacked Aero-Structure Drilling Process and Equipment (ECSASDPE)” focuses on the staff exchange between the partners of EU and China, and the development of key enabling techniques and equipment for the orbital drilling process of stacked AL/CFRP/Ti. It meets the objectives and requirements of the Marie Skłodowska-Curie Actions: Research and Innovation Staff Exchange (RISE), by establishing multiple bridges between European and Chinese institutions.
The objectives of the project are given as follows:
• Establish a long-term research cooperation platform through the ECSASDPE joint programme by exchange of researchers for short periods during the project. At least three new research proposals for both the EU and Chinese funding programmes will be prepared, and visits between partners will be arranged during and after the project period. As the research work is fully supported by partners’ existing projects and their own resources, in such a case, a long-term research cooperation platform ECSASDPE will be firmly established, and will be in function even after the project period.
• Exchange ideas and technology concepts for further development of novel machining processes and innovative productive equipment for effectively and automatically producing satisfactory holes on AL/CFRP/Ti stacks. All the consortium partners have been actively working on international, national and regional research projects in robotics and automation, composite material machining, surface integrity for many years. The advanced knowledge and expertise will contribute to the development of new technologies on ECSASDPE.
• Strengthen research partnerships through staff exchanges and networking activities between European research organisations and Chinese institutions. Partners can learn from each other the new science and technology developments of orbital drilling technique and equipment technologies and benchmark them against their own developments. Each partner will have at least one publication on average each year, giving more than 32 joint publications in total. The consortium targets at least 3 patent applications during the project period.
• Take a synergistic approach to the research areas and explore novel methodologies and applications for potential major scientific and technological breakthroughs by optimal combination of the different backgrounds and disciplines from the partners.
The ultimate goal of ECSASDPE is to set up a long-term international and inter-sector collaboration consortium through research and innovation staff exchanges between 8 world-recognised institutions in the cutting-edge research area of high value manufacturing with promising applications in scientific and engineering sectors. The synergistic methodologies achieved by ECSASDPE will serve as the building blocks of the stacked composite material machining mechanism, equipment design, process monitor and control, and machining quality metrology and characterisation and scale up application, and thus enhance the leading position of the consortium for the scientific and technological progresses in high value manufacturing. This project is divided into six inter-related work packages: (1) Setup of knowledge base and road mapping; (2) Fundamentals of drilling process; (3) Key techniques for Equipment development; (4) System integration and performance verification; (5) Dissemination and exploitation, and (6) Project management. The work packages integrate all activities that will lead to the accomplishment of all the project objectives within 48 months.

Work performed

A number of machining process for stacked AL/CFRP/Ti composite have been investigated, and the applications and user requirements for the proposed ECSASDPE technologies have been defined. Different robot-assisted stacked composite machining techniques have been reviewed. The fundamentals for helical drilling including damage mechanism and suppression methods, machining quality characterisation and evaluation methods, and machining parameter optimisation have been developed. The analytical model of cutting forces under steady state conditions has been developed for a special milling tool, which integrates the differential cutting forces along the cutter axis and considers the peripheral and bottom edges that participated in the cutting simultaneously. A number of cutting experiments are conducted for Ti–6Al–4V. The validity of the analytical model has been demonstrated by a series of cutting-verified tests. The influence of cutting variables on the cutting force during helical milling of CFRP has been analyzed based on the cutting experiments. The influence of tool wear on the cutting force is also analyzed. An investigation has been done to study the time varying temperature of the CFRP workpiece in helical milling process under various cutting conditions. The proposed temperature prediction model is capable of simulating the temperature distribution of CFRP workpiece with the movement of end mill. The effect of cutting conditions on machined CFRP surface integrity has been investigated using Taguchi DoE methods. The machining process has induced changes in the CFRP surface roughness, surface void fraction and depth of subsurface affected zone.
A simple, easily visualized yet effective approach for the type synthesis of a family of overconstrained 1T2R parallel mechanisms. It then establishes criteria to select structures best suited to building 5-DOF hybrid PKMs for machining applications. A simple and effective algorithm is developed to automatically select a set of independent/irreducible source errors being identified. A hierarchical strategy for source error estimation and pose error compensation. The proposed MSVD algorithm suitably modifies a part of the small singular values.

Final results

Overconstrained 1T2R parallel mechanisms can be visualized as being composed of a spatial limb plus a member of a class of planar symmetrical linkages. Drawing directly on the structures and evaluation criteria proposed here, a novel 5-DOF hybrid PKM module named TriMule is presented. A significant potential advantage of the new design over the established Tricept design arises because its geometry enables the integration of all the joints connecting to the base link of its planar linkage into a single compact part, thereby allowing the module weight to be dramatically reduced. Having determined with confidence that the TriMule design is competitive with the established Tricept design, its kinematic, static, and dynamic analyses have been fully investigated and reported.
A screw theory based approach for error modeling of the hybrid robot has been established by considering all possible source errors including the encoder offsets, the structural errors in joint and links, and the rigid body misalignments of the machine frame with respect to the workpiece frame. The experimental results show that the maximum volumetric position/orientation errors of 60um/0.04° within a task workspace of can be ensured after the fine calibration.

Website & more info

More info: https://warwick.ac.uk/fac/sci/eng/research/grouplist/measurement/ecsasdpe/.