3DCS FEA Compliant Modeler - Finite Element Analysis and Tolerance Analysis

Dimensional Control Systems | 2017 All Rights Reserved
3DCS FEA Compliant Modeler
Finite Element Analysis as part of
3DCS Tolerance Analysis software

Available in All 3DCS Platforms
3DCS FEA Compliant Modeler is
an Add-on module available for
all versions of 3DCS, including
all integrated versions and the
stand alone version (multi-CAD)

Value of Compliant Modeler
Increase the accuracy of your variation analysis by simulating the effects of clamping,
welding and bending, or from gravity and thermal influence.
● Add variation from process and environmental forces to your model for a more
comprehensive analysis.
● Design to account for process
● Optimize processes to reduce variation such as riveting sequences, clamps and
bending.

What is Compliant Modeler?
Compliant Modeler is an add-on module for 3DCS Variation Analyst Software.
Compliant Modeler uses mesh files from an FEA Preprocessor to simulate the
effects on parts and materials from processes, both environmental processes like
gravity and heat, as well as manufacturing processes like welding, clamping, bolting
and riveting.
Compliant Modeler solves the deformation as part of the variation analysis, adding
the variation from deformation and process to the stack up.
Using a Stiffness Matrix from a Solver, 3DCS simulates the deformation from the
process in conjunction with your Variation Analysis.

Reasons to Use Compliant Modeler
Deformation in parts causing less accurate variation analysis results
Over Constrained assemblies in the model
Parts deforming or has more than 3 primary datums
Clamping sequences and locations need optimizing
Welding, bolting, riveting in the model
Concentrated forces
Springback issues
Gravity, stresses or residual forces
Thermal deformation causing variation in use or production

Compliant Modeler Requirements
Increased Hardware Requirements
• 3DCS FEA Compliant Modeler adds advanced analysis in addition to the normal
analysis. In order to keep analysis time down, higher level hardware
specifications are recommended.
Finite Element Analysis - FEA Experience
• To generate the output files from the FEA Solver, experience with
FEA Analysis is highly recommended. This will improve the
accuracy of the files and analysis.

WHY USE COMPLIANT MODELER?
What kinds of scenarios does Compliant Modeler help analyze

One Software, Two Analyses
One Software for the entire analysis:
Apply your Finite Element Analysis (FEA) in the same tool as your variation analysis,
determining any interactions and reducing the need for training in other solutions.

Optimize Processes
• Find the optimal weld, bolt or riveting sequence
• Find the optimal amount of welds, bolts and rivets
needed
• Find the optimal placement of welds, bolts and
rivets
• Reduce variation as well as cost by removing
unneeded processes

Simulate Springback
Springback from clamping,
bending or flexing parts
Useful for aluminum
parts and sheet
metal assembly
processes

Clamping, Welding, Bolting and Riveting
One degree of freedom or all degrees of
freedom can be constrained using clamp move
● Simulating Joint between 2 parts:
> Spot Weld :
> Bolting :
> Fastener :

Gravity
1. Released from tooling
2. Weight of parts move
parts after manufacturing
and assembly
Example: Rear Fascia sags after released from tooling

Thermal (Environment)
Expansion from thermal effects in the environment or the function of parts (exhaust pipes) can
cause variation and issues down the line.
Simulate the expansion and variation caused by heat and how it affects your assembly.

Over Constrained Parts
● Simulating an over constrained assembly:
• A part deforms to another part
• A part which has more than 3 primary datums
• Can be simulated with Bend moves in 3DCS base software, using Compliant
Modeler is approximately 14% more accurate.

HOW DOES COMPLIANT MODELER
WORK
How does Compliant Modeler function in conjunction with 3DCS modeling

FEA Mesh Files
Compliant Modeler allows the user to apply an FEA Mesh file to a part or multiple parts.
• These need to be generated from an FEA Software.
• The FEA Software is not needed for any analysis
Once the Mesh file is applied to the part, Compliant Moves are added to simulate different
kinds of processes and forces.
The Deformation changes the nominal position, allowing further tolerance analysis stack
ups to determine overall variation results.

Process Flow – Model Creation
CAD
• CATIA
• NX
• Creo
• Other (Multi-CAD)
FEA • Abaqus Mesh File
• Hypermesh Mesh File
SIM • 3DCS Variation
Analyst

Are the Results Accurate?
Running the FEA Analysis in 3DCS versus running it in a separate FEA solver
Weld Study Comparison

MODELING PROCESS
How do you add 3DCS FEA Analysis to your existing models

Process Flow – Model Creation
CAD
• CATIA
• NX
• Creo
• Other (Multi-CAD)
FEA • Abaqus Mesh File
• Hypermesh Mesh File
SIM • 3DCS Variation
Analyst
Load CAD Model into 3DCS
Create and Export Mesh file
- Material Properties
Load Mesh and
Apply to parts
- Change nominal
position

Workflow Summary
• Moves to Simulate Force
• Utilize Finite Element Analysis
Solver (FEA)
1. Model in CATIA V5
2. Create Mesh in Abaqus
3. Run Analysis in 3DCS

Example Model
Example: Rear Fascia Gravity
Problem: Rear Fascia sags after being released from
tooling
CAD

CAD Model Opened in 3DCSCAD

Complete 3DCS Model
Complete All:
1. Moves
2. Tolerances
3. Measurements
3DCS

Material Properties
 Fascia composed of basic plastic material
FEA MESH

Export Mesh File from FEA
Solver
Map Nodes Across Geometry
1. Mass Matrix (Gravity)
2. Mesh overlay (Thermal)
FEA MESH

Mesh Applied to Part
• Measurements added to measure the effect
GAP Between Rear Fascia and Quarterpanel
3DCS

Output Results (Changes to Gap)
Measurement
Effect of
Gravity (mm)
Effect of
Thermal
(mm)
Total
Variation
(mm)
M1 2.71 5.80 8.51
M2 2.28 4.60 6.88
M3 1.83 3.58 5.41
M4 1.79 3.40 5.19
M5 2.64 4.26 6.90
M6 2.25 3.52 5.77
M7 1.52 2.21 3.73
3DCS

COMPLIANT MODELER BEST PRACTICES
Tips on using Compliant Modeler

Mesh File Creation
NOTE: Mesh file should
be created by an FEA
specialist.
•You need an individual mesh file for each
compliant part in the DCS model.
One Part, One
Mesh File
•If modelling an assembly as one part then the
mesh file needs to be created as an assembly
with connections between parts in the
assembly.
If Assembly is 1
Part, Then Mesh
Needs to be an
Assembly
•Number of nodes per part can be judged
based on part geometry. Increasing number of
nodes per part might increase the accuracy
but can result in slower simulation time.
More Nodes, More
Accuracy, More
Time Simulating
Optimum mesh file
size is 10mb or less.
The part mesh file from
an FEA pre processor
does not need to have
any boundary
conditions. DCS creates
boundary conditions.

Modeling Best Practices
First step is creating the whole model including
all MTMs! (Moves, Tolerances, Measures)
Build Rigid Body First  Then Add Compliant Moves

Modeling Best Practices
● While writing compliant moves, all compliant parts should be fully constrained before
doing any further operation such as Weld, Forces, Thermal, Gravity etc. A part can be fully
constrained using:
o One point in a Hard/Coincident Clamp Move (using 6dof FEA files)
o Three points in a Hard/Coincident Clamp Move (using 3dof FEA files)
o 6 points in a Soft Clamp Move.
o Position 3 points(1 point in 6dof) having x, y & z checked.
● It is recommended not to mix and match Hard and Soft clamp in one move.

Thermal Best Practices
If simulating thermal deformation, create your thermal move and pick all the points that
have a thermal deformation and input the change in temperature.
Check the thermal move section in help file to understand the difference of having a
thermal deformation on whole part and on some points on the part.

Clamping Best Practices
While unclamping/unpositioning, need to make sure the assembly/parts are still fully
constrained after unclamping/unpositioning.
When simulating a multi-stage assembly, unclamping must be a 2 move process.
In the first move you unclamp all but the points needed to fully constrain the assembly and
then use Skip Deformation option in an Unclamp Move for remaining clamps.
Skip Deformation option removes the clamps from the software memory but does not
deform the part.
Skip Deformation Unclamp Move should be the last move in the 1st fixture stage.

FEA Mesh Creation Best Practices
Make sure the FEA files are supported by stiffgen/Compliant Modeler!
Refer to help file for supported files.
Product Mesh File Extension Stiffness Matrix Extension
Abaqus .inp .mtx
Nastran .bdf, .blk, .dat, .nas .bdf
Optistruct .fem, .parm .dmig
MSC Nastran .dat .pch

● Make sure consistency of units is maintained while creating the mesh file. For
reference to consistency of units see the DCS help file.
● If using Stiffgen to create the FEA files then select the mesh file units in stiffgen.
● If you have multiple FEA solvers available on your machine, make sure to select the
same FEA solver that was used as a pre-processor for creating mesh file.
● It is recommended to create 6 Degree of Freedom (DoF) FEA files for a shell mesh.
● You can only create a 3 Degree of Freedom (DoF) FEA file for a solid mesh.

● Select Mass Matrix/Thermal load option in stiffgen if you have Gravity or Thermal
Expansion resp. in your model.
● It is recommended to always have a 6 Degree of Freedom (DoF) thermal load file for shell
mesh.
● Once you hit Generate FEA Files, make sure the batch process ran successfully and the files
were generated. If you see an error then check the .dat or .msg files in the dcsFEA_DATA
folder for any error messages.
For Thermal / Gravity

Nominal Build Best Practices
1. Create the Input FEA Data move and select all the compliant parts and corresponding
mesh/stiffness files in it. Move it above all the compliant moves in the tree.
2. Deactivate all the compliant moves and hit nominal build and check all the DCS points are
linked to FEA nodes using FEA Point Linking Wizard.
3. If everything looks good, activate all the compliant moves and hit nominal build again.
4. If you have any unrealistic deformation of points in the model, make sure to check the
consistency of units in FEA files.

ADDITIONAL EXAMPLES
What other results can be obtained from Compliant Modeler

Over Constrained Assembly
● Model 1: Two piece rail model
● Objective: Simulate an over constrained assembly taking into account
Manufacturing Process and Gravity to calculate:
o Spring back due to manufacturing process.
o Deformation
o Reaction Forces

Results
Nominal Build
Rigid Body Gravity Weld 1 Unposition Clamp Base Force Weld 2 Unclamp
Gap(mm) 5.00 3.75 3.83 3.75 0.00 0.00 0.00 4.80
Reaction
Force(N)
0.00 4.01 3.55 3.94 8.46 9.13 22.26 0.32
2000 Sample (Range)
Gap(mm) 4.75

Exhaust Pipe
● Model 2: Exhaust Pipe
● Objective: To simulate the effect of change in temperature to calculate
deformation.
Measurement Deformation(mm)
M1 5.58
M2 5.57
*All of these calculations include component
and assembly dimensional variation

Automobile Hood Bumper Placement

Fender
Hood
Hood is under-flush to Fender with high variation

Add a pair of bumpers to contour the Hood to the Fender and
reduce flush variation…
but where?

1. Front 2. Mid 3. Mid2 4. Upper
Determine the location of lowest flush variation between
Hood and Fender.
Simulate the placement of Bumpers at (4) locations:

Flush variation measured at these locations

1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
3.2
1 2 3 4 5 6 7 8
Est.RangeVariation(mm)
Rear - Mid - Front
No
Front
Mid
Mid2
Upper
Avg

2.7
2.8
2.9
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
1 2 3
Est.RangeVariation(mm)
Front - Mid - Rear
No
Front
Mid
Mid2
Upper

1. Front
2. Mid
3. Mid2
4. Upper 2.173 mm
2.172 mm
2.305 mm
2.328 mm
2.483 mm0. None
Mid2 bumper location is best for Hood to Fender flushness.

3DCS FEA Compliant Modeler - Finite Element Analysis and Tolerance Analysis

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