Technical Papers & Journals

CMM Calibration

Rich Dittman, Brian Wallin

In an effort to standardize the calibration process for Coordinate Measuring Machines (CMM) across GE Aerospace facilities, Brian Wallin and I conducted a comprehensive review of existing calibration practices. Our investigation revealed a lack of uniformity in the calibration standards being applied, with variations in the use of ASME B89 and ISO 10360 standards across different facilities and suppliers.

Upon detailed analysis of these standards, we identified ISO 10360-2009 as the most suitable calibration standard for recommendation due to its comprehensive and consistent approach. The ISO 10360-2009 standard provides clear guidelines for the performance verification of CMMs, ensuring that measurements are accurate and reliable. This standard was chosen for its ability to address the diverse needs of GE Aerospace facilities and suppliers, providing a common framework for calibration.

To address the inconsistency in calibration requests to OEMs and third-party calibration sources, we developed a standardized Statement of Work (SOW) for CMM calibration. This SOW was formulated in collaboration with industry leaders such as Renishaw, Hexagon Manufacturing Intelligence, and East Coast Metrology. The SOW outlines specific requirements for calibration procedures, including the use of certified artifacts, environmental conditions, and detailed reporting of calibration results. By establishing these guidelines, we aim to ensure that calibration results are consistent and reliable regardless of the service provider.

The implementation of this standardized calibration process is crucial for maintaining the health of CMM equipment. Regular monitoring and adherence to these calibration standards help minimize downtime and ensure accurate measurement results. This proactive approach to equipment calibration supports the overall goals of GE Aerospace in terms of Safety, Quality, Delivery, and Cost (SQDC), with safety being the most critical factor.

By adopting the ISO 10360-2009 standard and the standardized SOW for CMM calibration, GE Aerospace facilities can achieve higher efficiency and reliability in their measurement processes. This initiative not only enhances the performance of CMM equipment but also contributes to the overall operational excellence of GE Aerospace.

Numerical Balancing | Revolutionizing Metrology with Numerical Certainty and Accurate Autonomous Data Evaluation

Thomas Gendera, Prof. Dr.-Ing. Georg Kampmann, Ingobert Schmadel, Prof. Dr.-Ing. Milan Horemuz, Nick Turicek

A scientific discovery has been made of a new natural constant derived from a novel mathematical process developed for 30+ years, Numerical Balancing. Balancing uses equation symmetry logic (not a model) to determine reality with absolute geometrical and numerical accuracy through an Inner Reference / True Value. This removes measurement/numerical uncertainty in all calculations. Balancing applies across disciplines and dimensions; this paper will focus on 3D metrology applications.  

Current/traditional data analysis methods require subjective, biased data manipulation (e.g. strategies for alignment, filtering, fitting, etc.). This means a given data set can produce various results. Fundamental flaws of these methods are not maintaining raw data fidelity, ability to handle any data type without bias (homogeneous, heterogeneous, mixed), and lack of a True Value. A True Value is needed to determine the accuracy of a calculation process (e.g. we know 2+2 = 3.7 is off by 0.3 because we know the true value is 4). The combination of aforementioned issued causes current measurement results to have numerical uncertainty.

Numerical Balancing is an autonomous process to evaluate raw data in a neutral numerical coordinate system before model application. The advantage being, all the previously necessary, subjective strategies are obsolete with only one possible result per data set. Numerical Balancing finds the Inner Reference for every data set, determining its accuracy with certainty. All data is utilized (absolute fidelity) – the consistent data (balance range) is automatically determined per data set and separated from numerical leverages (outside balance range).

These are selected metrology applications:

Evaluating standard geometries like spheres. After measuring spheres, Numerical Balancing determines the balance range accuracy versus numerical leverages in the measurement point cloud. This independently evaluates probe/sensor accuracy. Knowledge about the position and amplitude of numerical leverages can be used to diagnose the root cause such as noise, bad readings or physical defects in a probe.

Evaluating machine capability/accuracy using Numerical Balancing in combination with a traceable, climate invariant 3-dimensional reference body. First, spheres are evaluated individually to determine probing/sensor accuracy. Once the sensor passes the accuracy check, the sphere centers are used in a balanced 12-parameter transformation to give volumetric accuracy and main geometric parameters (scaling/positioning and squareness). This is the first and only true 3-dimensional and numerically certain tool for accurate 3D machine capability testing.

Evaluating discrete point clouds to make alignment-free comparisons of nominal vs measured using automated measurement systems. As a foundation, individual features are evaluated with numerical balancing, giving a balance range accuracy, numerical leverage information, location and feature parameters. Lastly, all features are used in a transformation based on Numerical Balancing that minimizes the maximum deviation in 3D. One overall achieved balance range value in combination within the autonomous identification of numerical leverages gives actionable results. This eliminates the need for secondary systems for correlations, precision fixturing for alignment and false positive / false negative results caused by measurement uncertainty.

There are many future developments (e.g. autonomous object recognition) for Numerical Balancing in metrology, which will also be mentioned in the full paper.               

Performance Evaluation of an Automated Laser Tracker System for the Vera C. Rubin Observatory

Guillem Homar

The Vera C. Rubin Observatory’s Simonyi Survey Telescope (Simonyi Telescope) is an 8.4m telescope now in the final testing phase, on Cerro Pachon in Chile. To fulfill the Rubin Observatory scientific objectives of conducting a decade-long time domain survey of the optical sky, the Legacy Survey of Space and Time (LSST), the telescope requires delivering a consistent exquisite image quality over its 3.5 degrees field of view (FoV). This is accomplished using a sophisticated active optics system (AOS) and perfect alignment. 

Building on the established use of laser tracker technology during telescope integration, we now report the first alignment results for the Symoni telescope optical system; the LSSTCam, the largest digital camera ever built, and the telescope's secondary mirror (M2) relative to its primary/tertiary mirror. Using the Leica AT930 laser tracker system, we characterize the alignment of LSST Cam and M2 with respect to the telescope’s optical axis and assess the system’s ability to maintain alignment within stringent tolerances.

This work also presents a detailed analysis of observed drifts in the alignment measurements over time. These findings confirm the metrology system’s capability to support precise alignment during final integration and highlight important considerations for maintaining optical performance during operations.

Solving the existential question: How to accelerate throughput without sacrificing quality?

Emily Elizabeth

An aerospace engine manufacturer under pressure to improve production line performance tasked its leaders with finding opportunities to expedite their current processes without impacting final quality. The Head of Quality immediately identified his IBR inspection lead times as a bottleneck in their overall process – it was wrought with manual effort and a wait time of 17 hours for a single IBR. He offered a proposal to the team: “If we moved away from touchpoint CMM, and instead, utilized a non-contact option, we might be able to reduce total IBR inspection times by 50%.”

In this session, we’ll review how the Head of Quality Control approached his hypothesis with executives and the proposed the testing methodology to prove his conclusion. In addition, we’ll review real results of the recommendation implemented on the production line – including the technical specifications, application design, and performance metrics for both inspection reports and business bottom line.

Key Takeaways:

• Methodologies for presenting metrology test scenarios within your organization’s leaders
• Alternative approaches to consolidate inspections of myriad IBR features
• Best practices for measuring complex geometry while avoiding quality sacrifices

Metric potential of surface normal measurements from a lowcost camera. Work in progress and future potential

Stuart Robson, Hannah Corcoran, Lindsay MacDonald, Vijay Pawar, Samanta Piano and Mojtaba A. Khanesar

Photogrammetric imaging principles are highly flexible, capable of delivering high accuracy marker-based metrology, 3D surface reconstruction from microscopically small objects up to planetary scales. In the metrology area, cameras are used with active techniques, for example, the projection of light onto surfaces as points, lines, fringes, and random patterns. This paper presents an opportunity to take an active lighting technique “RTI” which enables reconstruction of surface normals from sequential images made with a static low-cost camera and constellation of lights. The technique has been widely applied in cultural heritage imaging to generate high quality visual reconstructions but is less well known in the field of metrology where its outputs might be regarded as qualitative and visually compelling but not quantitative. This presentation will give an example of cultural heritage reconstruction made for a national UK museum exhibition illustrating the capability to record highly detailed metallic surfaces which would challenge many industrial metrology sensing systems. The basis of the technique will be explained, followed by illustrated examples that highlight the challenges that need to be met to deliver metric quality surface normals from the technique. Comparisons will be drawn from what can currently be achieved with a low-cost camera synchronised with a constellation of infrared LEDs against reference surfaces scanned with a metrology industry state of the art triangulation laser scanner.

ORCHESTRATING PRECISION: THE ROLE OF STRATEGY IN HIGH-PRECISION QUALITY CONTROL

Donnie Brown

Measurement strategies for Coordinate Measuring Machines (CMM) are critical in achieving precise, consistent, and efficient inspections of geometric features in manufactured parts. 

Educating the Next Generation of Metrologists

Dr. Ed Morse

Edward Morse is the Director of UNC Charlotte's Center for Precision Metrology and is the Norvin Kennedy Dickerson Jr. Distinguished Professor of Mechanical Engineering. His research interests include large scale metrology, geometric tolerancing,...

Digital Calibration Certificates and QIF, the Quality Information Framework

Jacob Brooks

Although the manufacturing sector has made great strides in the adoption and implementation of industry 4.0 principles, a great deal of manufacturing information is still transmitted manually or using proprietary file formats. The Quality Information Framework, or QIF, is an XML-based system for carrying model-based design, quality, and metrology information between disparate software packages. Despite the breadth of the QIF standard, existing versions of the QIF schema are insufficient to define a full digital calibration certificate (DCC). In this work, we describe additions and modifications to QIF necessary to represent digital calibration certificates.  These additions to QIF enable the digital representation of information such as the accreditation of inspecting organizations, document metadata, calibration results, and environmental conditions present at the time of calibration activities.

A discussion of this work includes the organizational structure of digital calibration certificates using existing QIF infrastructure and data types consistent with relevant standards and common best practices. The development of software tools suitable for generating and manipulating DCCs is also discussed in this work. This enables software vendors to incorporate DCC manipulation into their software packages.

Ultimately, adoption of digital calibration certificates ensures the fidelity of metrology information as it moves throughout or between organizations. Digital calibration certificates have been provisionally incorporated into the draft QIF 4.0 model as a result of this work. If fully utilized, this DCC structure could enable automated documentary traceability and improve both the fidelity of transmitted calibration information and the efficiency of quality procedures.

SPIFI: Spirit Feature Inspection

Mark Haynes

Spirit Feature Inspection system (Spifi) is a first-of-its-kind technology for aerospace manufacturing.  Spifi is an inter-connected network of devices enabled by precision 3D positional tracking in the aircraft coordinate reference frame.  Utilizing a distributed computing architecture, the system presents a means of 3D tracking for an unlimited quantity of devices as well as interactive HMIs utilized for control and review of inspection related to fastener head height, skin quality, foreign object debris (FOD), and more.   The technology achieves precision positional tracking across a dynamic industrial factory space.

Spifi enables a semi-automated inspection process that reduces the workload for inspectors not only in the inspection of features but in the reporting process as well.  The level of automation and flexibility makes Spifi ideal for replication across multiple programs for aerostructure inspection.  With Spifi, it’s now possible to digitally record 100% of the hand-installed fasteners’ head heights.  This enables an unprecedented ability to perform statistical process control and root cause corrective action for fastener installation quality, and 100% of escapements can be prevented.  Any potential disputes can be cross-verified with the detailed digitally documented historic record.   

Spifi is a gateway technology with the potential to revolutionize the precision aerospace assembly industry.  Future applications include skin quality discontinuity tracking, skin quality dents, fastener torqueing, manual riveting monitoring, general task monitoring, data projection, virtual reality assembly instructions and real-time augmented reality assembly, and autonomous mobile robot guidance and control.

Spifi is a system capable of cross-program functionality, high replication across assembly stations, and proliferation into new applications within a single assembly station.  The future of aerospace manufacture is evolving with the capability that Spifi offers to the manufacturing process.

Mirrored Surface Use and Measurement in Spacecraft Assembly and Test

Bob Elliot

Mirrored surfaces such as cubes and flat mirrors have been used to align spacecraft components for decades.  These mirrored surfaces were initially measured with optical instruments and as technology advanced laser trackers have become an option for measuring these features.  This white paper and presentation will describe how and why mirrored surfaces are used on spacecraft components, early measurement techniques and how mirrors are measured with a laser tracker.  The advantages and disadvantages of the measurement methods will be discussed along with case studies that show schedule savings resulting from transitioning to modern tools.