Richard Leach

Richard Leach
University of Nottingham | Notts · Institute for Advanced Manufacturing

BSc MSc PhD DSc CEng CPhys FInstP FHEA
ERC Adavanced Grant holder - AI-SURF

About

662
Publications
393,187
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
10,381
Citations
Citations since 2017
356 Research Items
8208 Citations
201720182019202020212022202305001,0001,500
201720182019202020212022202305001,0001,500
201720182019202020212022202305001,0001,500
201720182019202020212022202305001,0001,500
Introduction
My current interests are the dimensional measurement of precision and additive manufactured structures. My research themes include the measurement and characterisation of surface topography, development of methods for measuring 3D geometry, X-ray computed tomography and uncertainty analysis. I have particular interests in developing optical techniques in combination with artificial intelligence.
Additional affiliations
June 2018 - January 2022
Taraz Metrology
Position
  • Managing Director
November 2014 - present
University of Nottingham
Position
  • Professor
August 2010 - present
Harbin Institute of Technology
Position
  • Professor
Description
  • Lecturing in metrology
Education
November 2014 - November 2014
The University of Warwick
Field of study
  • Surface Metrology
September 1997 - November 2000
The University of Warwick
Field of study
  • Surface Metrology
September 1991 - June 1994
Brunel University London
Field of study
  • Industrial Measurement Systems

Publications

Publications (662)
Article
Full-text available
In this review, the use of x-ray computed tomography (XCT) is examined, identifying the requirement for volumetric dimensional measurements in industrial verification of additively manufactured (AM) parts. The XCT technology and AM processes are summarised, and their historical use is documented. The use of XCT and AM as tools for medical reverse e...
Article
A comprehensive analysis of literature pertaining to surface texture metrology for metal additive manufacturing has been performed. This review paper structures the results of this analysis into sections that address specific areas of interest: industrial domain, additive manufacturing processes and materials; types of surface investigated; surface...
Article
The scope of this review is to investigate the main post-process optical form measurement technologies available in industry today and to determine whether they are applicable to industrial-grade metal additive manufactured parts. An in-depth review of the operation of optical three-dimensional form measurement technologies applicable to metal addi...
Article
Lack of assurance of quality with additively manufactured (AM) parts is a key technological barrier that prevents manufacturers from adopting AM technologies, especially for high-value applications where component failure cannot be tolerated. Developments in process control have allowed significant enhancement of AM techniques and marked improvemen...
Article
Full-text available
Camera-based methods for optical coordinate metrology, such as digital fringe projection, rely on accurate calibration of the cameras in the system. Camera calibration is the process of determining the intrinsic and distortion parameters which define the camera model and relies on the localisation of targets (in this case, circular dots) within a s...
Article
Full-text available
As the need for the manufacturing of complex surface topographies increases, traceable measurement with known uncertainties can allow a manufacturing process to remain stable. Material measures are the link in the chain that connects the surface topography measurement instrument’s output to the definition of the metre. In this review, the use of ma...
Article
Full-text available
Close-range photogrammetry can be used to reconstruct dense point clouds of an object with very high surface coverage, making it useful for manufacturing metrology tasks such as part inspection and validation. However, compared to competing techniques, data processing times can be slow. In this paper we present a method to autonomously remove the b...
Article
Full-text available
Data fusion enables characterisation of an object using multiple datasets collected by various sensors. To improve optical coordinate measurement using data fusion, researchers have proposed numerous algorithmic solutions and methods. The most popular examples are Gaussian process (GP) and weighted least-squares (WLS) algorithms, which depend on us...
Article
Full-text available
Optical coordinate measurement systems, such as fringe projection systems, offer fast, high-density measurements of arbitrary surface topographies. The versatility, speed and information density of fringe projection measurements make them attractive as in-situ measurement devices and autonomous inspection systems. However, the complex nature of the...
Article
Full-text available
Manufacturing has recently experienced increased adoption of optimised and fast solutions for checking product quality during fabrication, allowing for manufacturing times and costs to be significantly reduced. Due to the integration of machine learning algorithms, advanced sensors and faster processing systems, smart instruments can autonomously p...
Conference Paper
Full-text available
This work aims to investigate the performance of a trinocular sphere-based pose measurement system using components, algorithms and processes that prioritise metrological quality. Results from our approach are compared with binocular measurements using a reference laser interferometer. It is shown that introducing trinocular constraints to a multi-...
Conference Paper
Full-text available
The metrological characteristics framework introduced in ISO 25178-600 combines the different influence factors that contribute to the uncertainty of a measurement into a list of seven explicitly stated metrological characteristics which when propagated through an appropriate measurement model allow for an evaluation of measurement uncertainty [1]....
Conference Paper
Full-text available
Most existing fitting methods are designed for two-dimensional profiles or they are task-specific, e.g., they are often designed for one specific type of surface. In this paper, we present SURF-FIT, a universal fitting method for structured surfaces. SURF-FIT is a generic method that can be universally used for any type of structured surface (sinus...
Conference Paper
Full-text available
Approximate scattering models have gained popularity over the past years due to their simplicity and fast computational speed to predict scattered light [1, 2]. In contrast to rigorous scattering models which use numerical techniques to solve Maxwell's equations, approximate models mostly neglect the effect of the polarisation of the incident light...
Conference Paper
Full-text available
Quality assessment of a manufactured part is critical to ensure its functionality, especially for high-value parts in aerospace, automotive and health industries. Additive manufacturing (AM) is capable of fabricating parts with almost no geometry constraints due to the layer-by-layer processing nature. However, it is difficult to determine the qual...
Conference Paper
Full-text available
Approximate and rigorous methods are widely used to model light scattering from a surface. The boundary element method (BEM) is a rigorous model that accounts for polarisation and multiple scattering effects. BEM is suitable to model the scattered light from surfaces with complex geometries containing overhangs and re-entrant features. The Beckmann...
Conference Paper
Full-text available
For accurate coordinate measurment using a camera-based system, any cameras and projectors must be accurately characterised (referred to in the wider literature as calibration). The accuracy with which characterisation features can be localised within images will determine the accuracy of the characterisation. The OpenCV library has functions for d...
Conference Paper
Full-text available
In metal laser powder bed fusion (L-PBF), the manufacturing process entails complex thermomechanical interactions that yield deviations from the nominal geometry. While these deviations are typically unwanted, not all are necessarily detrimental to the functionality of the part. In this paper, we describe a multi-sensing approach, where layer-by-la...
Article
Full-text available
Additive manufacturing is now regularly used for customised fabrication of parts with complex shapes and geometries. However, the large range of relevant scales, high slopes, step-like transitions, undercuts, alternation between dark and overly bright regions and other complex features present on the surfaces, in particular of metal additive parts,...
Article
This paper takes the broad topic of geometrical surface imperfections on manufactured surfaces and provides an overview of how they affect component functionality and how they may be detected and classified as defects or not. The presented overview considers both human visual inspection and machine vision-based approaches along with their evolving...
Conference Paper
Full-text available
A metrological characteristic common to all methods for areal surface topography measurement is the topographic spatial resolution (TSR), defined as the ability to distinguish closely-spaced surface features. This ability is limited in mechanical stylus instruments by the stylus tip geometry, while for instruments that rely on optical imaging, infl...
Conference Paper
Full-text available
We have recently developed a new method for surface characterisation combining light scattering and machine learning (ML). The method has been successfully applied to the binary classification (acceptable vs. defective) of micro-structured [1-4] and additive manufacturing (AM) surfaces [5-8]. The general idea is to shine laser light onto a surface...
Conference Paper
Full-text available
Optical coordinate measurement techniques are growing in popularity due to their high surface coverage and fast data acquisition time, and photogrammetry in particular has the further advantage of inexpensive component requirements. Although data acquisition is fast, data processing speeds can be relatively slow, particularly when high point cloud...
Article
X-ray computed tomography (XCT) is increasingly being used for evaluating quality and conformance of complex products, including assemblies and additively manufactured parts. The metrological performance and traceability of XCT nevertheless remains an important research area that is reviewed in this paper. The error sources influencing XCT measurem...
Conference Paper
Full-text available
This paper presents a frequency scanning interferometry (FSI) shortwave infrared (IR) setup developed for position and orientation measurement of industrial robots. Within contemporary and future industrial frameworks, robots in particular collaborative robots (cobots) will play an important role in ensuring safe and coherent automation of manufact...
Article
Full-text available
Quality monitoring for laser powder bed fusion (L-PBF), particularly in-process and real-time monitoring, is of importance for part quality assurance and manufacturing cost reduction. Measurement of layer surface topography is critical for quality monitoring, as any anomaly on layer surfaces can result in defects in the final part. In this paper, w...
Article
Full-text available
An international comparison of surface topography flatness deviation was carried out. The comparison involved twelve optical surface topography instruments (focus variation instruments, confocal microscopes and coherence scanning interferometers) from six European research laboratories. The results demonstrated the following: (i) The flatness varie...
Article
Full-text available
With the increasing adoption of Industry 4.0, optical metrology has experienced a significant boom in its implementation, as an ever-increasing number of manufacturing processes are overhauled for in-process measurement and control. As such, optical metrology for digital manufacturing is currently a hot topic in manufacturing research. Whilst conta...
Conference Paper
Full-text available
Measurement of laser-based powder bed fusion (PBF-LB) surfaces provides a promising solution for closed-loop quality control of the final parts. This paper presents a light scattering method to measure PBF-LB surfaces combined with one-class support vector machines (SVMs) for anomaly (defect) detection during the manufacturing process. With the one...
Poster
Full-text available
We categorised existing algorithms for point cloud registration into three categories: Gaussian process (GP) algorithms, weighted least square (WLS) algorithms and machine learning algorithms. These categories could be further classified into user-dependent and user-independent algorithms, based on whether the algorithm requests pre-defined mathema...
Article
Full-text available
The simultaneous measurement of all six degrees of freedom of motion error for a linear stage is significantly faster than methods that measure each degree of freedom separately. However, in current simultaneous measurement methods, error crosstalk issues significantly affect measurement accuracy. In this paper, a direct and simple crosstalk decoup...
Technical Report
Full-text available
MMT have had a productive and enjoyable year, despite the obvious effects of the pandemic. A number of students finished their PhDs and we had some new post-docs start. Two of our academics were promoted. The Midlands Centre for Data-Driven Metrology has made a good start, without being able to hold planned face-to-face events, and we have started...
Article
Full-text available
As machine learning becomes more popular in the precision engineering sector, the need for large datasets of measurement data increases. Due to the often manual, user dependent and labour-intensive measurement processes, collecting a large amount of data is often infeasible. It would, therefore, be desirable to collect a small amount of data on whi...
Article
The shape of constituent metal particles has a significant influence on the bulk properties of raw powder and the mechanical properties of manufactured parts. In this paper, we provide a method for automatic shape-based classification of metal powder particles. Firstly, X-ray computed tomography was used to obtain three-dimensional volume data of m...
Article
Full-text available
The capability of optical surface topography measurement methods for measurement of steep and tilted surfaces is investigated through modelling of a coherence scanning interferometer. Of particular interest is the effect on the interference signal and measured topography when tilting the object at angles larger than the numerical aperture slope lim...
Article
Full-text available
We propose an model for coherence scanning interferometry using familiar Fourier optics methods and the spectrum of plane waves for the case where light source spectral bandwidth limits the fringe contrast as a function of optical path length. The model is straightforward to implement, is computationally efficient, and reveals many of the common er...
Article
Full-text available
On-machine areal surface topography measuring instruments are required for fast and accurate measurement of parts inside production machines without reducing production rates. This paper presents the design and development of a compact focus variation microscopy sensor that can be integrated into various types of machine tools. The paper focuses on...
Article
Full-text available
In this work, we investigate tessellating cellular (or lattice) structures for use in a low 10 thermal expansion machine frame. We propose a concept for a lattice structure with tailorable ef-11 fective coefficient of thermal expansion (CTE). The design is an assembly of two parts; a lattice outer 12 part and a cylindrical inner part, which are mad...
Presentation
Full-text available
A review and classification of in-process measurement methods used in powder bed fusion by their observable process signatures, and a global summary of the achieved results in the literature.
Article
Full-text available
Positioning errors are a primary performance indicator of precision stages. Calibration of stage positioning errors usually requires expensive, specialised instruments or artefacts. In this paper, we introduce a simple and cost-effective, machine vision-based method for stage error calibration. The novelty is that we used an arbitrarily textured pl...
Conference Paper
Full-text available
To address the future challenges in quality monitoring of metal laser powder bed fusion, a novel method is proposed to detect topographic anomalies on layer surfaces, which may appear during the manufacturing process. The method combines light scattering and principal component analysis. Scattering patterns, experimentally generated from real surfa...
Conference Paper
Full-text available
The lack of quality assurance in additive manufacturing, and specifically in metal laser powder bed fusion (MLPBF), is a major barrier to the adoption of these technologies in high-value industrial applications. Despite its potential for producing complex components, MLPBF is afflicted by the occurrence of in-process defects that affect the integri...
Article
Full-text available
Strut-based lattice structures produced by powder bed fusion are prone to characteristic manufacturing defects that alter both their form and surface texture. Most studies in the literature focus on a subset of commonly observed defects, typically radius variation and strut waviness; surface defects remain relatively unexplored. Furthermore, there...
Conference Paper
Full-text available
We propose an instrument model for coherence scanning interferometry using familiar Fourier optics methods, the spectrum of plane waves, and the assumption that the light source spectral bandwidth is the dominant factor in determining fringe contrast as a function of optical path length. The model is straightforward to implement, is computationally...
Article
Full-text available
Automatic design of the number of sample points and sample locations when measuring surfaces with different geometries is of critical importance to enable autonomous manufacturing. Uniform sampling has been widely used for simple geometry measurement, e.g. planes and spheres. However, there is a lack of appropriate sampling techniques that can be a...
Conference Paper
For more details on the virtual CSI, please see http://www.light-am.com/en/article/doi/10.37188/lam.2021.009
Article
Full-text available
Maximum permissible errors (MPEs) are an important measurement system specification and form the basis of periodic verification of a measurement system's performance. However, there is no standard methodology for determining MPEs, so when they are not provided, or not suitable for the measurement procedure performed, it is unclear how to generate a...
Conference Paper
Full-text available
In optical surface texture metrology it is often desirable to have access to large quantities of surface data for the purpose of training statistical models. However, these measurements can be time consuming and require user input at many stages of the data acquisition. Generative adversarial networks (GANs) have proven useful in the areas of style...
Presentation
Full-text available
Optical form measurement techniques, including close-range photogrammetry and fringe projection profilometry, are increasing in popularity due to high-speed data acquisition and the non-contact nature of the measurement. However, these techniques are often labour intensive, computationally expensive and user dependent. A system wherein an object ca...
Presentation
Full-text available
Introduction to workshop on machine learning for precision engineering: Fuelled by the advent of high-speed parallel computing, the field of machine learning has ceased to be a mere research curiosity and has begun to be deployed in real industrial applications. At euspen’s 21st International Conference & Exhibition, we are pleased to present an i...
Article
Full-text available
The authors report a modification to the amplitude–wavelength (AW) maps for industrial X-ray computed tomography (CT) regarding their maximum slope limit [Formula presented] It was originally stated that “the maximum slope limit, [Formula presented] of a sinusoidal surface that can be measured by X-ray CT is set to ~90° (i.e., [Formula presented]#x...