Loughborough University
Leicestershire, UK
LE11 3TU
+44 (0)1509 222222
Loughborough University

Centre for Innovative and Collaborative Construction Engineering


Dr Leslie Sleath


The dimensional variation analysis of complex mechanical systems

Project Title

A systems engineering approach to the variation analysis of complex mechanical systems




Dr Paul Leaney
Dr John Petzing

Mr Dennis Sleath
Mrs V gaynor

Director of Research:
Professor Stephen Ison

Resarch Period

2006 - 2010

A systems engineering approach to the variation analysis of complex mechanical systems


Dimensional variation analysis (DVA) software first became available in America during the late 1970’s and early 1980’s. This DVA software was capable of simulating the accumulation of minor variations in component size, shape and location throughout the assembly process in order to predict the subsequent overall variation in the complete system. The then new DVA software was used by engineers at Ford and General Motors to analyse the probable variation behaviour of new vehicle systems under development. Simulation was found to offer substantial advantages over the tolerance stack methods used previously. Simulation produced more detailed and reliable information that enabled the engineering team to achieve a more robust system design and production process. Since then, the use of simulation to analyse the effects of component manufacturing and assembly variation has evolved into a new engineering practice known as Dimensional Management (DM). As an integral part of the product development process, the purpose of DM is to protect the dimensional integrity of a new product throughout its design, development and production. Today DM is increasingly practised in the UK automotive industry and now migrating into the aerospace and other manufacturing industries. The current DM methods are capable of providing a straightforward analysis of static systems. However, new methods are required to extend the DM capability to include the (a) the detailed analysis of more complex, dynamic systems, such as automotive suspension or power train applications, and (b) to establish the link between component variation and system performance. These areas of development are required to facilitate both broader and deeper application of DM methods and techniques.


The aim of this project is to advance the current DM capability by developing the application techniques required to:

• Adapt the current DM/DVA methods to model the behaviour and to provide a comprehensive analysis of dimensional variation in complex mechanical systems.
• Enhance the current DM/DVA methods to establish the interdependence between component variation and the operation/performance of the complete system.
• Progress towards an ‘open architecture’ style of analysis where DVA simulations can be used to generate data that can be exported/exchanged for analysis using other software.


The primary research method will be to conduct a series of type specific case studies. Each case study will investigate a different type of complex mechanical system, for example, automotive suspension systems, engine systems, gearboxes or latch mechanisms. The study of each system type will examine at least two different system designs, for example, automotive suspension systems can be sub divided into front and rear designs, McPherson struts, double wishbone or multilink designs.


The objectives for each case study and each system design are to:

• Define the operational and performance requirements for the complete system.
• Identify the geometric parameters that govern or influence the system operation and performance.
• Reverse engineer the system design to determine the sequence of operations used to manufacture and assemble the component parts.
• Determine the manufacturing constraints that control the spatial relationship between features on the same component.
• Determine the assembly constraints that control the spatial relationship between features on different components.
• Establish the known or likely variation characteristics of the individual component parts
• Analyse the variation behaviour of the system to determine the nature of the relationship between component variation and the operation and performance of the complete system.

The collective objective for all the case studies and the overall objective of this project is to: identify any common or similar elements or trends in the analysis of each system type/design that could serve as the basis to construct more generic application techniques that can be used across a range of different system types.



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The Centre Administrator
Loughborough University
LE11 3TU

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