Grid method studies of the geometrical uncertainties in free form and micro processes

Minev, Ekaterin 2012. Grid method studies of the geometrical uncertainties in free form and micro processes. PhD Thesis, Cardiff University. Item availability restricted.

Preview	PDF - Accepted Post-Print Version Download (8MB) | Preview
	PDF - Supplemental Material Restricted to Repository staff only Download (81kB)

Abstract

This research is devoted to the engineering of a generic, reliable and cost-effective method for the investigation of accuracy in layer based fabrication technologies. It begins with a review of the causes of deviations and uncertainties in component parts, analyses of the existing approaches for accuracy investigation and their limitations and disadvantages. The main focus of the research is the development of an original and convenient methodology capable of defining the dimensional uncertainties and accuracy of the technologies and the distribution of dimensional errors within the entire build area. The Grid Methodology is based on the discretisation of the object to allow the measurement, calculation, visualisation and analysis of part distortion in terms of linear and shear deviations from nominal. A single test piece and routine measurement procedure are utilised to estimate the distribution of the above entities; calculated in a similar way to the geometrical characteristics of strains in solid mechanics. The methodology was applied to research the causes of inaccuracy in the vertical direction of SLS Polystyrene. The presence of a critical dimension in height from where the distortion changes from shrinkage to extension was revealed and explained. The methodology was also utilised to estimate the necessary scaling factors to improve part accuracy, based on the calculated distortions. Implementation of the Grid Method to Micro Projection Stereolithography resulted in the ability to describe and estimate curling distortion in terms of angular deviations from nominal and separate it from linear distortions. - ii - Furthermore the application of the GM to the emerging micro-nano manufacturing sector has been shown to support the assessment of process capability. This provides a means of calculating process tolerances using results obtained from the single test piece. Investigation of the accuracy capabilities of three micro-processes was performed and their compatibility for designing process chains presented.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Engineering
Subjects:	T Technology > TS Manufactures
Uncontrolled Keywords:	Process accuracy; Rapid prototyping (RP); Calibration test peice; Selective laser sintering (SLS); Process capability; Micro manufacutring
Date of First Compliant Deposit:	30 March 2016
Last Modified:	19 Mar 2016 22:56
URI:	https://orca.cardiff.ac.uk/id/eprint/32291

Actions (repository staff only)

Edit Item