Robotic Processing of surfaces from additive manufacturing

Project Introduction

This project focuses on a very topical development - additive-manufacture (3D-printing) of complex metal components. However, the sheer versatility of the technology, in terms of the complex geometries and intricate structures that can be produced in a single component, also comes at a cost. That is, the resulting surface-qualities fall very far short of the nanometre tolerances needed for challenging applications - ranging from imaging-mirrors for satellite cameras, to precision bearings and human joint-implants. Post-processing is required, but this is hindered by various issues, including detailed materials properties and significant porosity. This project will grapple with these issues, with the aim of delivering optimised, fast, automated processes. A variety of advanced technologies will be brought to bear, including numerical modelling, diagnostic instrumentation, and computer-numerically-controlled (‘CNC’) and robotic surface-processing.

Project Details
The starting point of the project will be to develop a good grounding in the breadth of existing (and potentially new) demands for additively-manufactured components with ultra-precision functional surfaces. This will lead into familiarisation with what a “surface” means quantitatively, in terms of its shape (square, round…), form (spherical, flat…), mid-spatial frequencies (ripples) and texture (roughness). Dimensional tolerances are the key to ultimate performance in any application, and the student will be introduced to the physics and engineering considerations behind how they are defined. Clearly, it is necessary to measure surfaces, both to close the process-loop in manufacturing, and ultimately to assert conformance to specification. The student will have ample opportunity to learn the ‘tricks of the trade’, and use a suite of metrology instrumentation and supporting software during the project.
The student will be given expert guidance in identifying relevant Case-Studies, around which the experimental programme and data-analysis – the bulk of the project – will be organised. These Case Studies will include a range of different artefacts, such human joint replacements, industrial mould and die sets, and prototype light-weighted mirrors for space.

There will then be three main project-objectives. The first will be to undertake research into how and why defects from additive-manufacturing ‘print-through’ into ultra-precise post-polished surfaces, and the role of materials-aspects in this. The second will investigate the performance of various bound and loose abrasive processing-strategies on small ‘witness’ samples, aiming to manage print-through and achieve nanometre-quality surfaces. The third objective will be to apply the results to complex (“freeform”) components in their entirety, which introduces further complexities of both process and metrology. The end-point will be to demonstrate an effective end-to-end process-chain, starting with a CAD-model, manufactured by3D-printing, post-processed through an optimised series of process-steps, and supported by metrology.

The practical work will involve the use of computer numerically controlled (CNC) polishing machines, robot polishing, metrology instrumentation, and commercial and bespoke software. Structured trials using Taguchi Design of Experiment will be used to reduce the range of runs to manageable proportions in a statistically-valid way. Experimental results will be subject to estimates of uncertainty-of-measurement, including random and systematic effects.
The suite of equipment that will be used is located in Huddersfield’s new Laboratory for Ultra-precision Surfaces, at the STFC Daresbury National Science and Innovation Campus (near Warrington), where the student will be based. This will give the student ample opportunity for exposure to other work, facilities, activities and expertise within the wider Daresbury Campus community. Beyond that, the student will be expected to make visits as required to the Huddersfield campus (the Centre for Precision Technologies in particular), in order to use other specialist equipment, and to consult other experts in the field.