Spatial Kinematic-Chains and Ball-Joints.
When you cannot model a kinematic-chain on one Plane, it is usually a Spatial Kinematic-Chain.
A spatial kinematic-chain may have Cylindrical, Spherical and Helical-Joints. You can add spherical-joints. In Packaging, Textile, and Automation machines, the spherical-joint a common joint for spatial kinematic-chains.
See Ball-Joint Configurations.
IMPORTANT:
Ball-Joints and Mechanism Misalignment
In machines, engineers frequently use rod-end bearings in a mechanism to allow a small amount of misalignment between parts.
Do NOT use a Ball-Joint to model a mechanism when the primary function of the rod-end bearing is to compensate for misalignment, and to make sure the mechanism does not bind,
Use Pin-Joints to model the kinematic-chain on one Plane. But, of course, in your machine, use rod-end bearings.
Terminology (Glossary)
Term : |
Description |
|---|---|
Spherical Joint : |
A joint that joins a Point in two Parts. One of the Parts is a Connecting-Part. We use Ball-Joint as the element-name. |
Connecting Part : |
When we join a Part to other Parts with Ball-Joints, it has the derived-name of Connecting-Part. |
Rod-End Bearing: |
An engineer's name for a bearing that has 2 degrees-of-freedom |
Heim Joint : |
American term for Rod-End bearing |
Rose-Joint : |
British term for Rod-End bearing. |
Objective of this Tutorial
•To review different Planar and Spatial mechanisms. •To design a spatial mechanism that is frequently used in a packaging, textile, and assembly machines. |
