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. |
