Getting Started Tutorials - MechDesigner > Tutorial 2A: Four-bar Kinematic-Chains > Step 2.2: Add a Motion FB; Kinematic Vectors

Use Motions from MotionDesigner

In Step 1.6, the model is a Motion-Part that rotates with uniform angular velocity - it is a Crank.

However, Parts in packaging machines frequently have more complex motions.

We use a Motion FB to link a more complex motion in MotionDesigner to a Motion-Part in the model.

Objective of this Step

1.Move a Part with a motion that is more complex than constant angular velocity

2.Show the Kinematic-Vectors for a Point

Summary of this Step

1.Delete the Gearing FB between the Linear-Motion FB and the Motion-Dimension FB

2.Add a Motion FB to the graphic-area.

3.Connect a wire from the Linear-Motion FB to the Motion FB, and from the Motion-FB to the Motion-Dimension FB

4.Edit the Motion-Dimension FB.

5.Edit a Point to show its Kinematic Vectors.

You should also complete MotionDesigner Tutorials 2 and Tutorial 3 to change the motion design.

Video of this Step

Tutorial 2: STEP 2.1

•Add Motion FB

•Edit Motion-Dimension FB

Move the 'Motion-Part' with a Motion FB

GA-DeleteFB-Context

STEP 1: Delete the Gearing FB

To delete the Gearing FB

1.Mechanism-Editor: Click the Gearing FB (or wire) one time.

The Gearing FB element shows in the Selection-Window

2.Selection-Window: Right-click the Gearing FB in the Selection-Window.

3.Selection-Window: Click Delete element in the contextual-menu.

GA-AddMenuFB

STEP 2: Add a Motion FB to the graphic-area

To add the Motion FB

1.Mechanism-Editor: Click Kinematic FB toolbar> Add Motion FB

2.Mechanism-Editor: Click in the graphic-area.

The Motion FB is now in the graphic-area.

GA-AddMotionFB-wires

STEP 3: Connect wires between the Function-Blocks

1.Drag a wire from the output-connector of the Linear-Motion FB to the input-connector of the Motion FB.

2.Drag a wire from the Motion FB to the Motion-Dimension FB.

In the image, there is wire and wire between the FBs.

As the MMA increases from 0 to 360, the output from the Linear-Motion FB also increases from 0 to 360, which is now the input to the Motion FB.

The default-motion in MotionDesigner has a X-axis range from 0 to 360. The Y-axis of the Motion FB is now the Y-axis of the default-motion.

The output from MotionDesigner becomes the input to the Motion-Dimension FB.

Thus, the Motion-Part (Rocker) moves when you use Run menu (or toolbar) > Cycle with the default motion.

STEP 4: Cycle the kinematic-chain with the ALT+C key on your keyboard.

The Rocker moves, with the motion as specified in MotionDesigner. It completes one motion for each cycle (0 – 360) of the Master-Machine-Angle.

Instant Analysis: Kinematic Vectors

We are about to demonstrate that MechDesigner calculates the Position, Velocity and Acceleration of all Points at all times.

We will add a new Line to the Coupler, at a random place, and show its velocity and acceleration vectors.

GA-VelocityAccelerationVectors

STEP 1: Add a Line to the coupler

We use the same procedures to edit all Parts - we Edit the Part with the Part-Editor. There are many ways you can start the Part-Editor- See Step 1.3

Edit the Coupler Part:

1.Mechanism-Editor: Double-click its Part-Outline . The Part-Editor opens.

2.Part-Editor: Click Geometry toolbar > Add Line | Drag in the graphic-area to add the Line

3.Part-Editor: Geometry toolbar > Add dimensions and Add constraints to specify position of the Line.

4.Part-Editor: Double-click the new Line to close the Part-Editor.

Dialog-PointVectors-VelAccSelected

STEP 1: Show the Velocity and Acceleration Vectors:

1.Mechanism-Editor: Double-click any Point on a Part with a Green Part-Outline

The Point Properties dialog-box opens - see image.

2.Point Properties dialog-box: Click the Show or Hide Vectors separator

3.Point Properties dialog-box: Click the Show Velocity Vector and Show Acceleration Vector check-boxes

4.Point Properties dialog-box: Click the icon, to close the dialog-box.

Do 1-3 again to show the kinematic vectors of different Points, or to hide vectors for those Points that show vectors.

Note: Why Show Numerical Vectors?

There is no need to show them! And their values are slightly different from the normal Velocity and Acceleration Vectors.

We calculate the Numerical Vectors with a finite difference technique, and we evaluate Velocity and Acceleration Vectors with algebraic equations.

To reduce the differences, edit, by a small amount, the machine-angle. Use the Spin-Box tool of the Read-Write, Master-Machine Angle edit box.

Scale the Vectors

Scale buttons in the Feedback-Area.

V is for the Velocity-Scale and

A is for the Acceleration-Scale buttons in the Feedback-Area.

1.Click the up-button to increase the length of the vectors

- or -

1.Click the down-button to decrease the length of the vectors

About the Velocity and Acceleration Vectors in the graphic-area

•The show only when the Point moves relative to the Mechanism-Plane

•Their length is proportional to the Point's instantaneous Velocity and Acceleration

•The magnitude of the vectors shows at the arrowhead of each vector

•Edit the Vector colors in Application Settings > Colors tab > Graphic separator

•The Vectors update their values and length each machine-step - see Machine Settings dialog-box > Number-of-Steps

Notes:

If necessary, change the color of the graphic-area to see the vectors more clearly - see Edit menu >Application Settings > Colors tab > Graphic separator > Background