INTERFERENCE CHECKING
BY
Paul Thurber
When is a ½” not a ½”

What do you do if it does not fit

Who is responsible for the parts and pieces
History of Drafting
Traditional Paper Drafting
 Artwork
 Hard to update
 Hard to Store

The CAD Revolution
Computerized drafting
 Faster Drafting
 Easier Updating
 Easy To Store
 Instant Drawings Available

Drafting Practices
Drafter responsible for making parts fit
 To insure proper fit tolerances were used
 The more accurate the parts the closer the
tolerances were required
 Locations of features were none standard

Interference Was Engineers
Responsibility
Drafters made drawings
 Only did some drawings
 Complete Assembly
 Overall Performance

Tolerance Stacking a Problem

An accumulation of many tolerances a
problem

With multiple drawings careful checking
needed
No Clear Standards
The World Economy but no World
Standards
 How TO Convert from Measuring Systems
 Quality was Hard to Maintain

Change to Geometric Tolerances
Drafting practices changed
 Geometric tolerances were developed
 Consistent Drawing Features increases
accuracy

Interference Checking
Drafter was now responsible
 New standards aided interference
 Shop tolerances became standardized

The New 3D CAD
Can now draw in three diminsion
 Growing ability to see how parts fit
 Multiple views for one part
 Solid modeling becomes reality

Animation and CAD
The next revolution was part animation
 Exploding parts could be put together
 Overall planning and part manufacturing is
part of the computer world

CAD/CAM
Computer Aid Design Becomes Computer
aid Machining
 Drawings become machining programs
 Drawings used to automate ordering

Larger Role For CAD

CAD becomes a Major engineering tool

Automation of stresses and design
Interference
From the Drawing Into Shop
Floor Management
Interference checking goes beyond parts
 Shop floor management begins at the design
stage
 The checking of tolerances is only a small
part of the total capabilities

Assembly and Design
Drafting parts with Design Becomes Art
Work
 Optimization of assembly through
animation
 Complete Assembly Drawings

Assembly Is Automated
The new CAD/CAM
 Becomes point of assembly
 Interference checking is automated

Boeing Aircraft
Drafting becomes modular
 Can check out designs without parts
manufacturing
 Computer drafting becomes shop floor
management

Tsinghua University
Developed AOPDO
 Can make parts to optimize profits
 Complete package for Manufacturing

Interference Checking in
Assembly
The new programs aid in assembly
 Assembly functions can be automated
 Each Step is part of whole

Interference Checking Is Quality
The better the fit the higher the quality
 Quality is designed into the part
 Quality becomes a driving force

Quality is Automated
Interference of Quality needs reduced
 Quality is Automated

Winning Customers
Faster modular designs
 Customer needs addressed
 What is next

Conclusions
Old fashioned is hard to understand
 The next step is hard to understand
 Can we truly automate manufatcuring

References
“An integrated Framework for the
Assembly Oriented Product Design and
Optimization” by Qiang Su Ph.D. School
of Economics & Management Tsinghus
University
 “Geo-Metrics II” by Lowell W. Foster
 Boeing Aircraft Design Web Page
