07-geomagic non-contact whole-part inspection · non-contact whole-part inspection cmsc 2011...

Non-Contact Whole-Part Inspection

CMSC 2011 (Phoenix Arizona)

John Lockhart: Product Manager, Geomagic, Inc.Gabor Lukas: Senior Software Engineer, Geomagic, Inc. Mike Facello: Director Research and Development, Geomagic, Inc.

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Summary

• Historical background

• The paradigm shift in whole part inspection

• Solution: the correspondence data model

• The role of correspondence in:– Outlier removal

– Feature creation

– Alignment – GD&T Analysis

– Automation

• What’s Next

• Questions?



A Brief History

While CMM solutions have been employed since the 1960’s, non-contact technologies have been viable for inspection for less than two decades

In addition to laser and white light systems, recent advancements have increased the accuracy of computed tomography, CT, and dramatically reduced the cost.



At a First Glance the Benefits are Compelling

• Speed and Ad Hoc Inspection• Vastly superior coverage• Ease of use• Low cost• Wider variety of materials and environments• Increased coverage yields new analytical

results



However, There are Paradigmatic Differences

The CMM methodology defines many a priori assumptions about the data collected which do not exist in non-contact contexts.



A Need for New Techniques

Thus non-contact techniques require special solutions for new problems.

• Data Quality– Noise

– Outliers

• Data Semantics– Classification of data to features and surfaces

– Freeform geometry



The Correspondence Model

The approach to solving these problems we call Correspondence

Correspondence can be roughly defined as the application of reverse engineering and other mathematical techniques to define a common vocabulary for communication between test and reference objects.



Correspondence Answers the Question:

Which points belong to which features?

But does so in a way which is independent of any specific alignment or selection.

Correspondence mapping between a CAD and measured data



Why is this Important?

• Correspondence is automatable • Correspondence functions independently of

any specific alignment or set of test data

Accordingly, correspondence allows for the speed and comprehensive coverage of whole-part inspection while maintaining the automation and repeatability of CMM inspection.



Other Considerations

• Correspondence is an iterative process which is alignment independent and can be refined as more accurate mappings are created

• Correspondence is a general approach to which a wide variety of reverse engineering techniques can be applied.



The Correspondence Workflow

• Use of CAD reference to establish vocabulary for communicating with the test object – faces or features

• Initial Alignment• Topological mapping (reverse engineering and

mathematical techniques)• Correspondence creation• Application to outlier removal, automatic feature

creation, GD&T, feature comparison, and correspondence editing



Algorithmic Considerations• The correspondence algorithm starts from some hypothetical alignment in order

to match features of the reference model to the test object.

• This alignment is for finding initial areas of the segmentation, later these regions will grown and refined according to the inner geometry of the object.

• The proximity itself will not determine to which class a given area should be classified as the following picture illustrates:

Correspondence methods account for gross variation in data quality and measured data.



EditingOnce created, correspondence can be edited to better reflect design intent. Editing options should also be automatable throughout the process. The automatic calculation of shrinkage from boundaries is an important tool.

The mapping of nominal and measured data before and after correspondence editing.



Feature Creation

We use the term “auto-creation” to describe the automatic creation of features on the test object. When combined with PMI data design intent from the CAD model enables 100% automation of an inspection plan.

A cylindrical feature defined on the CAD and auto-created on the measured data via correspondence mapping



Alignment and Analysis

Correspondence is applied iteratively.

Feature based alignments are enabled via auto-created features which, in turn, enable refinements of an initial correspondence.



GD&TThe communication of design intent to the test object via correspondence enables automated GD&T results in a way similar to feature creation.

Correspondence mapping applied to the definition of a surface profile callout.



Automation

One of the main advantages of correspondence is that the techniques are independent of any particular alignment or manual selection.

This enables a high degree of automation and leverages the speed advantages of non-contact methods.



What’s Next

• More feature based semantics for use with non-CAD reference objects

• Application of other reverse engineering algorithms for better classification

• Continued enhancement of correspondence editing tools, e.g., segmentation.

• Leveraging of PMI Data



Questions?



07-geomagic non-contact whole-part inspection · non-contact whole-part inspection cmsc 2011...

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