Why Use the UG Model for Dimensional Control

Why Use the UG Model for Dimensional Control George Kovatchev Sitius Automation UG Users Group Conference Fall 2000 SITIUS

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 SITIUS

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 SITIUS

Preventive and Corrective Use Best-fit EDM electrodes Correct casting locators Identify cutter deflection SITIUS

How it’s done Geometry 2 D Drawings Manual CMM Program 3 D Cad Model Part Verification CMM Program SITIUS

How 2 D compares to 3 D • (+) No need to buy new CMM software • (-) Very difficult to inspect free-form surfaces • (-) Need to maintain 2 D drawings • (-) Low reproducibility • (-) Increased chance of errors • (-) Hard to keep up with engineering changes SITIUS

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 SITIUS

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 SITIUS

2 D vs. 3 D To CAD model - 30 minutes From 2 D drawings - never From 2 D drawings - 3 days To CAD model - 4 hours SITIUS

2 D Drawings vs. 3 D 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) SITIUS

Are all CAD based inspections equal? NO • • Access to the math data Integration between CAD/CAM/Inspection Accuracy, performance and usability Other factors SITIUS

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 SITIUS

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 SITIUS

Accuracy and reliability • IGES - low • Parasolid - high • Direct link - depends if there is a translation • Integrated - 100% SITIUS

Example of IGES translation 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. 053 mm up to -0. 111 mm, well below the lower tolerance limit of -0. 050 mm resulting in significant errors and repeated rework on the part. SITIUS

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

Avoiding data duplication is it important? • • Waste of time Source of errors Engineering changes Concurrent engineering SITIUS

Data duplication • 2 D Drawings - Yes • IGES - Yes • Parasolid - Yes • Direct link - Usually • Integrated - No if using User Defined Objects (UDO) SITIUS

Other benefits of using an integrated solution for CAD based inspection • 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 SITIUS

CAD based simulation SITIUS

Reporting Actual color-coded results GD&T reporting SITIUS

Updates SITIUS

Summary • • • Ability to work in 3 D 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! Please join us for a demonstration. SITIUS Contact Us. . . • on the web at http: //www. sitius. com • e-mail georgek@sitius. com SITIUS