Add Magnetic-Joint

See also : Magnetic-Joint dialog


What is a Magnetic-Joint?

A Magnetic-Joint pulls a circular Profile, that is in one Part, to become in continuous contact with an 'irregular' Profile, that is in a different Part.

The shape of the 'irregular' Profile can be derived from a Point-Cloud or a Profile added to a sketch-loop.

Why use a Magnetic-Joint?

A frequent application of the Magnetic-Joint is to reverse-engineer a cam. And then to find the motion of a Cam-Follower from the shape of the cam.

Prepare Magnetic-Joint

PREPARATION

Two kinematically-defined chains,  There must be a Profile in each kinematic-chain.

GA-AddMagneticJoint-0

KINEMATIC-CHAIN 1:

An irregular Profile2s as a child to a Part1s-red.
This might be a Curve derived from a Point-Cloud or a Profile from a sketch-loop.
Profile2s does not need to be a child to Part1s-red, it must only be a child to Kinematic-Chain 1.

In this model, a Part continually rotates in this model (it is a Crank). It might also be a Slider.


KINEMATIC-CHAIN - PART 2:

Motion-Dimension FB3s specifies the position of a Part5s
Motion-values at the input to Motion-Dimension FB are ignored after Magnetic-Joint is applied.
A circular Profile4s is a child to the Part5s
Part5s is pulled by the Magnetic-Joint so that the circular Profile4s becomes in continuous contact with the irregular Profile2s.
Profile4s does not need to be a child to Part5s whose position is defined by Motion-Dimension FB3s, it must only belong to a Part in Kinematic-Chain 2.

Add Magnetic-Joint

Add Magnetic-Joint icon

Machine Elements Toolbar : Add Magnetic-Joint icon

Menu:

Add menu > Mechanism sub-menu > Add Magnetic-Joint

Dialog :

Magnetic-Joint dialog-box

CM-AddMagneticJoint-1

ADD MAGNETIC-JOINT:

1.Click Machine elements toolbar > Add Magnetic-Joint
2.Click the Profile [or Point-Cloud]2s that is the irregular shape
3.Click the Motion-Dimension FB3s to 'drive' by the new magnetic-joint contact between the circular and irregular Profile.
4.Click the Profile4s with the circular shape.
5.Click OK-tiny-13-17 in the Command-Manager

 

GA-AddMagneticJoint-1

RESULT:

The Magnetic-Joint 'pulls' the two Profiles2s4s together.
The Magnetic-Joint FB5s shows in the graphic-area
When you cycle the machine, the two Profiles stay in continuous contact.
The Motion-Dimension FB3s becomes 'driven' by the Magnetic-Joint.

Magnetic-JointwithHorseShoe

Note:

The irregular Profile should:

NOT be to one side of the centre of rotation or its Origin
NOT form a 'horse-shoe' shape around the centre of rotation, or its Origin.
NOT have a radius-of-curvature that is less than the circular Profile.

If the irregular Profile is not acceptable, the circular Profile will jump to different contact solutions as you cycle the model.

Notes:

The Magnetic-Joint does not use 'closed mathematical equations'. The motion of the Magnetic Driven Part is 'solved' using optimization techniques. Thus:

The modeling is slower.
A Magnetic-Joint may fail if the Profiles cannot stay in continuous contact for a complete Machine Cycle.

See Also: Magnetic-Joint dialog-box, Add Profile, Sketch-Loop, Add Motion-Dimension FB; YouTube Video : http://youtu.be/IME9Eb4mpQE

Video:

 

How to...

Add Magnetic-Joint

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd