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.

To learn about Dyads.


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 - see Step 1.7: Edit the Length of the Crank.


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.

GST-Icon-AddMechanismEdit Kinematic-Chains

Step 2.1: A Crank-Rocker

Step 2.1A- The Concept of Dyads

Step 2.2: Add a Motion FB

Step 2.3: A Crank-Slider

Step 2.4: Change the Closure of the R-R-P Dyad

Step 2.5: A Slider-Crank

Step 2.6: A Scotch-Yoke

Step 2.7: Assemble your own Whitworth Quick Return Mechanism

Step 2.8: How to Model Pin-in-Slot Mechanisms

Step 2.9: How to Model a Pin in a Curved Slot