George KovatchevSitius Automation

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Why Use the UG Model for Dimensional Control

UG Users Group ConferenceFall 2000

About us

• Sitius Automation develops process oriented solutions that are fully integrated in commercial CAD systems

• We are Unigraphics Alliance Partner• We specialize in dimensional metrology

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Who needs CMM inspection

• Die designer – verify the tool against the part• NC programmer / CNC operator – improve the cutting process• Tooling engineer – make corrections to compensate for casting

deformations• QC manager – conform to company standards• Production technologist – maintain stable process• Assembly group – save time fitting• CMM operator – overtime, teach the engineers GD&T• The boss – keep the customer happy• INSURANCE

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Preventive and Corrective Use

Identify cutter deflection

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Best-fit EDM electrodes

Correct casting locators

How it’s done

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Geometry

3D Cad Model2D Drawings

CMM ProgramManual CMM ProgramPart Verification

How 2D compares to 3D

• (+) No need to buy new CMM software

• (-) Very difficult to inspect free-form surfaces

• (-) Need to maintain 2D drawings

• (-) Low reproducibility

• (-) Increased chance of errors

• (-) Hard to keep up with engineering changes

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How manual inspection compares to off-line programming

• (+) Highly adaptive– changes in setup– missing features– on-the-floor inspection– changes in requirements

• (+) Faster turnaround on low volume – tooling, inserts– EDM electrodes– prototyping– first article inspection

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How manual inspection compares to off-line programming

• (+) Works with manual machines– CMM’s– Laser trackers– Articulating arms

• (+) Easier to perform• (-) Increased chance of errors*• (-) Reduced repeatability and reproducibility*• (-) Requires operator• (-) Higher demand for CAD based solutions

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2D vs. 3D

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From 2D drawings - 3 daysTo CAD model - 4 hours

To CAD model - 30 minutesFrom 2D drawings - never

2D Drawings vs. 3D CAD Models

• Faster - sometimes by order of magnitude• Inspect any part• Increased repeatability and reproducibility• Reduced data duplication• Better way to inspect mechanical parts regardless of the

method (manual or off-line programming)

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Are all CAD based inspections equal?

NO

• Access to the math data• Integration between CAD/CAM/Inspection• Accuracy, performance and usability• Other factors

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Comparison by interface to CAD

• IGES, VDA-FS, STEP, DXF– Most of the commercial systems use IGES

• Parasolid– Maybe one

• Direct links– Some promise, none really work

• Integrated– Two for Unigraphics

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Time to start work

• IGES - from 5 min to 5 days

• Parasolid - from 5 to 20 min

• Direct link - should be fast

• Integrated - from 1 to 2 min

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Accuracy and reliability

• IGES - low

• Parasolid - high

• Direct link - depends if there is a translation

• Integrated - 100%

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Example of IGES translation

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Nominal points generated by the “industry leader” in CAD based inspection are compared with the actual Unigraphics CAD model. The CMM software uses IGES to translate the part. The profile tolerance is 0.100 mm (actual part needs to be between the red and the blue line). In effect the nominal hits are off from -0.053mm up to -0.111mm, well below the lower tolerance limit of -0.050 mm resulting in significant errors and repeated rework on the part.

Back to Unigraphics

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The same part checked in Unigraphics before and after best fit.

• Waste of time• Source of errors• Engineering changes• Concurrent engineering

Avoiding data duplication - is it important?

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• 2D Drawings - Yes

• IGES - Yes

• Parasolid - Yes

• Direct link - Usually

• Integrated - No if using User Defined Objects (UDO)

Data duplication

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• Access to solid information - very important for part verification and probe radius compensation

• Support for assemblies

• Graphical reporting and simulation

• Support for embedded GD&T

• Smart updates

• Macros, Parameters, Undo

Other benefits of using an integrated solution for CAD based inspection

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CAD based simulation

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Reporting

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Actual color-coded results

GD&T reporting

Updates

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Summary

• Ability to work in 3D• Accuracy and reliability• Notification of changes• Eliminate data duplication• Concurrent engineering

Do yourself a favor

If you design your part in Unigraphics inspect it there as well. This is your last step before you ship the part out. Do it right!

Thank you!

• on the web at http://www.sitius.com• e-mail georgek@sitius.com

Contact Us...

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Please join us for a demonstration.

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