Use of Skeleton Modeling


April 5, 2006 Facebook Twitter LinkedIn Google+ DMU


Use of Skeleton method greatly reduces design iteration time. This article explains how to build skeleton model and use the DMU capability to optimize the designs faster. This article is primarily aimed for CATIA V5 users having basic knowledge of CATIA V5 DMUKinematics.
Advantages
  • CATIA DMU (Digital Mock-up) V5 helps you create realistic 3D mock-ups to facilitate reviews, evaluate alternatives, and resolve design issues real time – without making costly physical prototypes of mechanism.
  • CATIA DMU V5’s robust visualization and review capabilities helps taking decision  in early phase of Product development.
  • CATIA V5 DMU delivers flexible simulation, analysis and validation capabilities to improve product quality.

 

 

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How to Start CATIA V5 DMU KINEMATICS  ?
Start CATIA V5 .
Go to Start – Digital Mockup – DMU Kinematics

 

Introduction of Basic kinematics Joints- CATIA V5 DMU
Introduction of Basic kinematics Joints- CATIA V5 DMU

 

Geneva Mechanism

 

CAM & Follower

 

 

How to Create Skeleton Model ?

When do we need Skeleton Model ?

  • When we want to create simulation for  big assembly structures (  like Automotive Seat assembly , Sunroof Assembly , Latch Assembly etc) , then we should go for  Skeleton Modeling Method.
  • When user want to do number of iteration while designing the kinematics , then user can go for skeleton modeling method.

 

BASIC STEPS to Create Skeleton Model

  • Create CATIA Skeleton assembly of parts which contains Lines & curves (  Lines & curves are representation of 3D CAD models ). The part containing lines & curves called as Skeleton parts
  • Apply Kinematics Joints between different skeleton parts. Run the Mechanism in the Skeleton Assembly
  • Import the sub mechanism in the Main CATIA Assembly.
  • Use Mechanism Dress-up Tool to link 3D CAD models & Skeleton parts with each other
  • Run the Mechanism in Main CATIA Assembly

All the above steps are explained below

TEST ASSEMBLY:  
WE WILL DISCUSS A VERY SIMPLE SLIDER CRANK MECHANISM TO STUDY SKELETON MODELING METHOD

 

Task :

  • Design Slider Crank mechanism (120mm Piston Stroke)
  • Simulate the mechanism – Check Clash / Clearance between Connecting Rod & Base )
  • Design Modification: -Reduce the Piston stroke by 10 mm

Step 1 :
Create Skeleton assembly structure in CATIA V5 which contains empty Skeleton Parts. Initially the skeleton parts will not contain any Geometry.

Step 2 :
Create Axis, Curves, Lines & Planes in skeleton parts (Crank, Connecting rod ,piston, Base) as per the mechanism Design requirement. These lines, curves & planes will be used to create Kinematic joints.
Example:- Crank skeleton part contains two axes which represents the two Hole axes. These axes will be used to create Revolute joints.( 1. Revolute Joint with Base 2. Revolute Joint with Connecting Rod)

Step 3 :
Complete the SKELETON ASSEMBLY for Slider Crank mechanism.

Step 4 :
Create Kinematics joints between Skeleton parts & complete the Slider crank Mechanism. Ensure the degree of freedom should be “Zero”.


Step 5 :
Run the Simulation in Skeleton Assembly. This completes your Mechanism Design using Skeleton parts.
Note: Use Simulation command  (DMU Generic Animation Toolbar-CATIA V5)  to run the simulation

 

Step 6 :
Import the Sub Mechanism into Main CATIA Assembly.

Main CATIA Assembly contains Skeleton Assembly & 3D CAD models of slider crank mechanism.
The 3D CAD parts are linked to the respective skeleton parts.

Step 7 :
Use Mechanism Dress-up Tool to link 3D CAD models & Skeleton parts with each other

Step 8:

Run the simulation in Main CATIA Assembly & do the clash / Clearance analysis at different mechanism positions.

Step 9 :
Clash found between Connection Rod & Base part. Modify the connecting rod to remove interference.

Modify the connecting rod to remove interference.
Run simulation again & check the clash.

Task :Design Modification: -Reduce the Piston stroke by 10 mm
Solution: Modify the distance between two hole axis of Crank Skeleton by 5mm to reduce piston stroke by 10mm

Step 10 :
Update the Skeleton Assembly & run the simulation.
The respective 3D CAD model of Crank will also get modified as it is linked with the Crank skeleton part.
This completes your task.
Now using this Skeleton model , you can do the number of Design changes (iterations) in very short time.

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