Dialog: Function-Block: Continuous-Crank

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Dialog: Function-Block: Continuous-Crank

Continuous-Crank

See also Add Continuous-Crank

It is often the case that a motion is designed for a Tool, but the Tool is not driven directly. A different Part drives the mechanism. The motion and forces are transmitted through the mechanism from a Driving-Part to the Tool-Part.

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

There is also the case in which the Driving-Part completely rotates, but with a non-uniform rotating speed. This is a special-case. To make sure this can happen, the Driving-Part must be exactly the correct length.

The Driving-Part becomes a Crank that rotates continuously in one direction as the Tool-Part moves with your motion-design.

This is one application of the Continuous-Crank FB.

Open Continuous-Crank FB dialog-box

MD-GA-FB-ContinuousCrank

Edit the Continuous-Crank FB:

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

- or -

1.See How to Open a Dialog-Box  

The Continuous-Crank dialog-box is now open.

Continuous-Crank dialog-box

MD-DIALOG-FB-CONTINUOUS-CRANK

STEP 1: Select Crank Behavior and Direction

Crank Behavior

CONTINUOUS - the Part will rotate continuously.

reversing - the Part will rotate to ~180º, and return back to ~0º.

Crank Direction

If Crank Behaviour is Continuous, then:

Counter-Clockwise - the Part will rotate in the Counter-Clockwise direction

Clockwise - the Part will rotate in a Clockwise direction

If Crank Behaviour is Reversing, to change Crank closure, see Change-Dyad Closure.
MD-FB-CONTINUOUSE-CRANK-0

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 Message 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-box.

Messages at the bottom of the dialog:

When you select a Part as the Continuous Crank, there will be a Message.

Message

Meaning

Valid

The Part can be a continuous Crank

Failed assign pivot-Point

We could not find the rotating-axis.

Impossible crank length:

Geometry is inconsistent

This often the case that the Motion-Part does not move, and thus the length of the Crank must zero(0).
MD-FB-CONTINUOUSE-CRANK-1