Large Scale Metrology In Aerospace Assembly

The paper presents a review of the principles and state of the art in instrumentation used to make large scale measurements within aerospace assembly. The ability to measure large artefacts accurately is a key enabling technology to improve quality and facilitate automation. Particular emphasis is placed on issues of uncertainty with the importance of acceptance criteria explained and verification standards compared and discussed. The fundamental technologies deployed are explained including laser trackers, indoor GPS and photogrammetry. Commercially available systems are compared in terms of uncertainty, range and deployment related issues

Integrated Dimensional Variation Management in the Digital Factory

This paper describes how dimensional variation management could be integrated throughout design, manufacture and verification, to improve quality while reducing cycle times and manufacturing cost in the Digital Factory environment. Initially variation analysis is used to optimize tolerances during product and tooling design and also results in the creation of a simplified representation of product key characteristics. This simplified representation can then be used to carry out measurability analysis and process simulation. The link established between the variation analysis model and measurement processes can subsequently be used throughout the production process to automatically update the variation analysis model in real time with measurement data. This ‘live’ simulation of variation during manufacture will allow early detection of quality issues and facilitate autonomous measurement assisted processes such as predictive shimming. A study is described showing how these principles can be demonstrated using commercially available software combined with a number of prototype applications operating as discrete modules. The commercially available modules include Catia/Delmia for product and process design, 3DCS for variation analysis and Spatial Analyzer for measurement simulation. Prototype modules are used to carry out measurability analysis and instrument selection. Realizing the full potential of Metrology in the Digital Factory will require that these modules are integrated and software architecture to facilitate this is described. Crucially this integration must facilitate the use of realtime metrology data describing the emerging assembly to update the digital model.</p

Design for measurement assisted determinate assembly (MADA) of large composite structures

This paper describes how Measurement Assisted Determinate Assembly (MADA) can facilitate the lean production of aerospace structures, provided that the structure is designed for MADA. A novel wingbox design and production process is used to illustrate this. The aerospace industry has not benefited from the significant reductions in production cost and cycle time that can result from greater assembly efficiency, part-to-part interchangeability and the use of flexible automation. This is largely due to the very high accuracies required across large scale assemblies. The use of metrology can reduce process steps, reduce the reliance on costly hard tooling, reduce the requirement for manually intensive and time consuming re-working at late stages of assembly, and allow low cost flexible automation to place tools to the required accuracies. The generic MADA process is presented together with guidelines for the design of structures to enable MADA

Kinematic Analysis and Optimization of Bicycle Suspension

Bicycle suspension is increasingly used to improve performance and facilitate the use of smaller wheels for folding bicycles, unwanted activation due to pedalling and braking forces can however result in energy losses. This paper presents a kinematic analysis leading to a Suspension Activation Ratio (SAR) which is the ratio of the suspension activation force to the pedalling force and its experimental verification. The SAR may be used as a performance metric to compare suspension designs and an objective function for suspension design optimization where the SAR is minimized for all possible gear ratios. Suspension geometry thus optimized shows agreement with optimal pivot positions found by empirical studies. Previous work has involved dynamic simulation and experimentation to estimate energy losses; however it is difficult to apply this analysis to rapidly evaluate different suspension designs for performance evaluation or design optimization. The kinematic design approach presented here provides the first step in suspension design which should precede dynamic design to optimize spring and damping rates

Uncertainty evaluation method for axi-symmetric measurement machines

This paper describes a method of uncertainty evaluation for axi-symmetric measurement machines. Specialized measuring machines for the inspection of axisymmetric components enable the measurement of properties such as roundness (radial runout), axial runout and coning. These machines typically consist of a rotary table and a number of contact measurement probes located on slideways. Sources of uncertainty include the probe calibration process, probe repeatability, probe alignment, geometric errors in the rotary table, the dimensional stability of the structure holding the probes and form errors in the reference hemisphere which is used to calibrate the system. The generic method is described and an evaluation of an industrial machine is described as a worked example. Expanded uncertainties, at 95% confidence, were then calculated for the measurement of; radial runout (1.2 μm with a plunger probe or 1.7 μm with a lever probe); axial runout (1.2 μm with a plunger probe or 1.5 μm with a lever probe); and coning/swash (0.44 arcseconds with a plunger probe or 0.60 arcseconds with a lever probe)

Uncertainty of the Measurement of Radial Runout, Axial Runout and Coning using an Industrial Axi-Symmetric Measurement Machine

This paper describes a method of uncertainty evaluation for axi-symmetric measurement machines which is compliant with GUM and PUMA methodologies. Specialized measuring machines for the inspection of axisymmetric components enable the measurement of properties such as roundness (radial runout), axial runout and coning. These machines typically consist of a rotary table and a number of contact measurement probes located on slideways. Sources of uncertainty include the probe calibration process, probe repeatability, probe alignment, geometric errors in the rotary table, the dimensional stability of the structure holding the probes and form errors in the reference hemisphere which is used to calibrate the system. The generic method is described and an evaluation of an industrial machine is described as a worked example. Type A uncertainties were obtained from a repeatability study of the probe calibration process, a repeatability study of the actual measurement process, a system stability test and an elastic deformation test. Type B uncertainties were obtained from calibration certificates and estimates. Expanded uncertainties, at 95% confidence, were then calculated for the measurement of; radial runout (1.2 µm with a plunger probe or 1.7 µm with a lever probe); axial runout (1.2 µm with a plunger probe or 1.5 µm with a lever probe); and coning/swash (0.44 arc seconds with a plunger probe or 0.60 arc seconds with a lever probe)