﻿ Getting Started Tutorials - MechDesigner > Tutorial 2A: Four-bar Kinematic-Chains

# Tutorial 2A: Four-Part kinematic-chains

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# Tutorial 2A: Four-Part kinematic-chains

## Four-bar Kinematic-Chains

Four-Part Kinematic-chains - which you may call a four-bar mechanism, four-bar linkage, or even four-bar -

They are the basis of the most frequently used mechanism in packaging machines.

This tutorial uses Pin-Joint and Slide-Joint elements. We combine the joints in different ways to configure the mechanism in different ways.

### Objective of this Tutorial

To build kinematic-chains that have a total of four Parts and four Joints.

Note:

Try to add Parts that are approximately equal in length to the Parts that are in the tutorial images. If necessary, edit the length of a Part -.

### Terminology: Reminder from Tutorial 1

 Plane : the flat surface to which we add a new Mechanism-Editor. The Front-View of each Mechanism-Editor is perpendicular to its XY-Plane - NOT relative to the Global XYZ axes Mechanism-Editor : the workspace that includes the Mechanism-Plane , the graphic-area, the contextual -toolbars, and the Mechanism-Editor name-tab. Part : an element that becomes the moving, or fixed, rigid-bodies in the machine. Part-Outline : the symbol for a Part. We click the Part-Outline to  select the Part. Joint : general term for an element that constrains the relative movement between two Parts. Pin-Joint : a joint that constrains two Points to move together, with one Point in two different Parts. Kinematic-Chain : two or more Parts joined together with one or more Joints. Kinematically-Defined : Part or Kinematic-Chain that moves in a manner as specified by at least one Motion-Part. Parts that are kinematically-defined have Green Part-Outlines. When a Part has a: •Green Part-Outline: the Part is a kinematically-defined Part. We also call it a Solved Part. •Blue Part-Outline: the Part is not a kinematically-defined Part. We also call it an Unsolved Part Our target is to make all Part-Outlines Green, ALWAYS. Motion-Part : a Part, that is kinematically-defined, whose motion is precisely specified with a Motion-Dimension FB Function-Block : a tool to plan motions for Motion-Parts. It provides motion-values at its output-connector. Motion-Dimension FB : a Function-Block(FB) that identifies a Motion-Part. Linear-Motion FB : a Function-Block(FB) whose output follows the Master-Machine-Angle. The default output increases from 0 to 360 as the MMA increases from 0 to 360. You can edit the starting value, to be different to the MMA. Gearing FB : a Function-Block(FB) with which you can apply parameters to the motion-values at its input, in the form of a linear equation, to give different motion-values at its output. Master-Machine-Angle : the clock that, when you cycle the machine, moves at a constant rate from 0 to 360, again and again. The position of each kinematically-defined Part is a function of Master-Machine-Angle. Rocker : a Motion-Part that rotates with a specific motion relative to a different Part. Crank : a Motion-Part that rotates continuously with a uniform rotary motion.

### Terminology: Tutorial 2

 Slide-Joint : a Kinematic-Joint that constrains Line is one Part to be collinear with a Line in a different Parts. Slider : a Motion-Part that slides with a specific motion relative to a different Part. It may index progressively, slide continuously (as a 'conveyor'), or reciprocate back-and-forth. Dyad : a Dyad is a kinematic construction of: •2 Parts, and •3 Joints Dyad Closure : a different way to assemble the same Dyad. Motion FB : a Function-Block(FB) that is a link to a Motion in MotionDesigner Crank-Rocker : a kinematic-chain with one Motion-Part (the Crank) and one Dyad that has three Pin-Joints, and the output oscillates (rocks) back-and-forth. Crank-Slider : a kinematic-chain with one Motion-Part (the Crank) and one Dyad that has two Pin-Joints and one Slide-Joint, and the output reciprocates (slides) back and forth.