Dialog: Function-Block: Continuous-Crank

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Dialog: Function-Block: Continuous-Crank


See also Add Continuous-Crank

It is often the case, in a multi-part mechanism, that the motion is designed for the Tool-Part (the Part with the tooling).

The Tool-Part is often driven by a different Part in the mechanism, which is the Driving-Part. We derive for you the motion of the Driving-Part from the Tool-Part by inverse-kinematics.

Usually, with a Cam mechanism, the Driving-Part is an oscillating Cam-Follower that is moved by a Cam.

However, there is also the case in which the Driving-Part rotates fully, but with a non-uniform speed. This is a special-case. To make sure this can happen, the Driving-Part must be exactly the correct length, and its motion, also 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


Edit the Continuous-Crank FB:

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


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 Behaviour is Continuous, then:

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

Clockwise - the Part rotates in a Clockwise direction

If Crank Behaviour 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 graphic-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.




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