Dialog: Function-Block: Continuous-Crank

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Dialog: Function-Block: Continuous-Crank

Continuous-Crank

See also Add Continuous-Crank

Usually, in a multi-part mechanism, you design the motion for a Tool-Part (the Part with the tooling), and MechDesigner uses Inverse-Kinematics to calculate the motion of a Follower-Part or a Servomotor.

With a Cam mechanism, the Driving-Part is a Follower, and the Follower oscillates.

However, with a Servomotor, there is also the case in which the Driving-Part rotates completely, but with a non-uniform rotating speed. This is a special-case. To enable this special-case, the Driving-Part must be the correct length, and its motion, derived by inverse-kinematics from the motion of the Tooling, is more complex.

This is one application of the Continuous-Crank FB.

How to open the Continuous-Crank FB dialog

MD-GA-FB-ContinuousCrank

Edit the Continuous-Crank FB:

1.Double-click the Continuous-Crank FB in the graphics-area

OR

1.See How to Open a dialog

The Continuous-Crank dialog is now open.

Continuous-Crank dialog

Continuous-Crank dialog - not enabled

Continuous-Crank dialog - not enabled

STEP 1: Select Crank Behavior and Direction

Crank Behavior

CONTINUOUS - the Part rotates continuously.

reversing - the Part rotates to ~180º, and then return back to ~0º.

Crank Direction

If Crank Behavior is Continuous, then:

Counter-Clockwise - the Part rotates in the Counter-Clockwise direction

Clockwise - the Part rotates in a Clockwise direction

If Crank Behavior is Reversing, to change Crank closure, see Change-Dyad Closure.
Continuous-Crank dialog- enabled

Continuous-Crank dialog- enabled

STEP 2: Activate the Not Selected box

1.Click in the box labeled Not Selected

The Box is now Orange. You can now select a Part.

STEP 3: Click a Part that you want to be the Continuous-Crank

1.Click a Part in the graphics-area or Assembly-Tree.

The Continuous-Crank Part must have a Pin-Joint that joins it to the Base-Part.

The Part immediately changes its length so that it can rotate continuously or oscillate by 180º. If there is a problem, see Messages at the bottom of the dialog.

STEP 4: Confirm the behavior is as expected

1.Do Run toolbar > Cycle Continuously (ALT+C)

STEP 5: Click OK-tiny-11-15 to close the dialog.

Messages at the bottom of the dialog:

When you select a Part as the Continuous Crank, there is be a message at the bottom of the dialog.

Message

Meaning

Valid

The Part can be a Continuous Crank

Failed assign pivot-Point

We could not find for you the rotating-axis.

Impossible crank length:

Geometry is inconsistent

For example, the Motion-Part does not move, and thus the length of the Crank must zero(0).
Continous-Crank dialog

Continous-Crank dialog