Open source 3D printed instrumentation

Abstract

Open source hardware has the potential to revolutionise the production of scientific instruments, benefiting researchers across the globe by reducing cost and enabling more collaborative design. This thesis presents three pieces of 3D printed instrumentation I worked on during my PhD, the OpenFlexure block stage, the ACute3D autocollimator, and the 3DRO distance sensor. All of them have been developed as open source hardware and software with the aim to make high quality instrumentation accessible to everyone. The OpenFlexure block stage is a monolithic XYZ translation stage that uses a novel flexure hinge mechanism to achieve sub-100 nm resolution. It was originally designed by Dr Richard Bowman, and I contributed to its development by characterising its performance through a series of performance characterisation experiments. When motorised with readily available stepper motors, the block stage can be used to automate or remote-control experiments in the laboratory. I played a leading role in the development and testing of a gradient ascent algorithm that allows the block stage to perform fully automated fibre coupling. In a separate project, three novel flexure geometries that can potentially improve the robustness and loading capacity of the block stage were studied through simulations using the method of finite element analysis. These novel flexure geometries are suitable for 3D printing using standard filament deposition printers and standard slicing packages with the thin dimension orthogonal to the print bed. By studying the maximum stress under first order bending and the stiffness against second order bending of a range of flexure hinges of each geometry, performance comparisons were made against the flexure hinge currently used in the block stage design.

The ACute3D is a digital laser autocollimator, capable of optical noncontact angle measurement in two orthogonal directions over a maximum measurement range of 7220 arcsec by 5290 arcsec. Its novel design exploits the geometric freedom of 3D printing to realise a monolithic optomechanical assembly that is compact, stiff, and resistant to drift. The unit is extremely linear, especially over the middle third of the maximum measurement range. Experiments were performed to assess its measurement uncertainty at different working distances and mechanical stability under different thermal conditions. At working distances below 267 mm, the measurement uncertainty is less than 3 arcsec over the middle third of the measurement range. Under temperature stabilisation to less than half a degree Celsius variation, the mechanical drift is sub-arcsec in both measurement directions.

The 3DRO is a trigonometric sensing distance sensor that is intended to be used as a digital read-out on machine tools. Requiring only a collimated laser diode and a Raspberry Pi camera in the assembly, it can be locally produced in any country across the globe. Another key advantage of the distance sensor is customisability, the measurement range and the outer casing geometry can both be tailored to suit the need of a specific machine tool. To demonstrate the distance sensor is ready for practical use, it was used as a digital readout on a lathe in Tanzania to machine a test piece. The machined piece had a maximum dimensional error of 0.2 mm over a total length of 61 mm, showing the distance sensor can be used to upgrade old manual lathes to produce workpieces that are adequate for most engineering purposes.

Date of Award	4 Dec 2023
Original language	English
Awarding Institution	University of Bath
Supervisor	William Wadsworth (Supervisor), Richard W. Bowman (Supervisor) & Julian Stirling (Supervisor)