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Posted April 24, 2008
Speed up joint creation process using
Automatic Conversion of Assembly Constraints
The Joint Axes
Standard Joints
Some possible Assembly Constraint Configurations
(between 2 components)
Equivalent Standard Joints Created by Automatic Conversion
Resulting degrees of freedom
Insert
Revolution
-No Translation
-Rotation around Z-Axis
1
Face & Face
+
Edge & Edge
Prismatic
-Translation along Z-Axis
-No Rotation
1
Face & Face
+
Face & Face
Prismatic
-Translation along Z-Axis
-No Rotation
1
Face & Face
+
Axis & Axis
Prismatic
-Translation along Z-Axis
-No Rotation
1
Edge & Edge
or
Axis & Axis
Cylindrical
-Translation along Z-Axis
- Rotation around Z-Axis
2
Point & Point
Spherical
- No Translation
- Rotation around all 3 Axes
3
Face & Face
or
Flush & Flush
Planar
- Translation along X & Z-Axis
- Rotation about Y-Axis
3
Point & Edge
or
Point & Axis
Point-Line
- Translation along Z-Axis
- Rotation around all Axes
4
Face & Edge
or
Face & Axis
Line-Plane
- Translation along X & Z-Axis
- Rotation about X & Y-Axis
4
Face & Point
Point-Plane
- Translation along X & Z-Axis
- Rotation about all Axes
5
No Constraints
Spatial
- Translation along all Axes
- Rotation about all Axes
6
No Constraints
No Joints Translated
-Remain Grounded
0
Tangent constraint
No Joints Translated
5
Fully constrained
Such as no degrees of freedom between components
No Joints Translated
-Components are welded together
-No relative motion
0
Fully constrained
Such as no degrees of freedom between components
Grounded
- if one of the components is grounded
0
Grounded
With or without constraints
No Joints Translated
-Remain Grounded
0
Notes:
1 In some cases a spatial joint will also be added in addition to some of the above joints if none of the components are grounded.
2 Number of joints created will not necessarily be same as the number of assembly constraints created
TOP 5 DYNAMIC SIMULATION TIPS
With Automatically Convert Translated Joints checked you can create more standard joints using standard assembly constraints within the simulation environment by pressing C (or Alt+C)
Create subassembly of components that have no relative motion between them
Use Weld parts for components that function as a unit or have similar motion
2D Contact is easier to control than 3D Contact
Redundant constraints occur only if an assembly is over-constrained. *
*
For example a door and frame has 12 degrees of freedom (D.O.F) between them. If we ground the frame then we only have 6 D.O.F for the door. We can constraint the movement of the door by either using any of the following examples:
Revolution Joint Remaining I D.O.F
Spherical Joint + Point-Line Joint Remaining 1 D.O.F
2 Revolute Joint Over-constrained by 5 D.O.F
By Wasim Younis, VDS Solutions Ltd
For further tips tutorials support visit: www.vdssolutions.co.uk
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