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# Mechanism | Add Magnetic-Joint

## 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 be in continuous contact with an irregular Profile, that is in a different Part.

The shape of the irregular Profile is calculated from a or it is the shape of a Profile.

### Why use a Magnetic-Joint?

A frequent application of the Magnetic-Joint is to reverse-engineer a cam, and to find the motion of a cam-follower from the shape of the cam.

### Prepare the Magnetic-Joint

 See also RULES There are two kinematic-chains - one with an Irregular Profile, and the other with a circular profile KINEMATIC-CHAIN 1: Irregular-Profile : a Curve calculated from a or a Profile. Irregular-Profile : is a child to any Part that is in a kinematically-defined chain, or it may be child to the Base-Part. In this model, the irregular-shape is a child to Part, which is a Rocker/Crank. KINEMATIC-CHAIN 2: Circular-Profile : a Profile. Motion-Dimension FB specifies the position of a kinematically-defined chain, in which the Circular-Profile is a child to Part In this model, Motion-Dimension FB specifies the position of Part in which the Circular-Profile is a child. Notes: •Part and Part will usually move relative to each other. •Part and Part will usually be in different kinematic-chains. •Part and Part might be in one kinematic-chain, but with at least two Motion-Dimension FBs.After you do Add Magnetic-Joint, Motion-Dimension FB, becomes driven by the Magnetic-Joint RULES Shape of the Irregular-Profile 1.Preferably, you apply a Tangent Constraint between the sketch-elements that define the shape of the Irregular-Profile. 2.|Radiusmin| of Irregular-Profile > Radius of Circular-Profile (taking the Circular-Profile to have a positive radius).Immediately before you do Add Magnetic-Joint 1.Home the model with the ALT+H key combination.With respect to which surface of the Irregular-Profile you want the Circular-Profile to be in contact : its Outside-Surface or its Inside-Surface: 2.Edit Motion-Dimension FB | Base-Value to move the Circular-Profile so that the: a)- Normal distance from Circular-Profile to the Irregular-Profile < 0.5 × Radius of the Circular-Profileor, equivalently, the: b)- Normal distance from the center of the Circular-Profile to the Irregular-Profile  < 1.0 × radius of the Circular-Profile

### Add Magnetic-Joint

 Toolbar : Machine Elements Toolbar Machine Elements Toolbar : Add Magnetic-Joint icon Menu : Add menu > Mechanism sub-menu > Add Magnetic-Joint Dialog : Magnetic-Joint dialog-box ELEMENTS: The Part on which the Irregular-Profile is a child. The Irregular-Profile - a Profile or a Curve calculated from a Point-Cloud The Motion-Dimension FB that will become driven by the Magnetic-Joint and the contact between the Circular-Profile and Irregular-Profile. The Circular Profile The Part to which the Circular-Profile is a child. ADD MAGNETIC-JOINT: 1.Click Run menu > Home  ( or the ALT+H key combination).2.Edit the Motion-Dimension FB | Base-Value to move the Circular-Profile to be near to Irregular-Profile3.Click Machine elements toolbar > Add Magnetic-Joint 4.Click the Irregular Profile5.Click the Motion-Dimension FB6.Click Profile7.Click in the Command-Manager RESULT: •The Magnetic-Joint pulls the Circular-Profile to be in contact with the Irregular-Profile. •A Point Symbol is at the contact. •The Magnetic-Joint FB shows near to the Point-Symbol•A Magnetic-Joint icon is near to the Motion-Dimension FB that becomes driven by the Magnetic-Joint. Notes: The Magnetic-Joint does not use closed-form mathematical equations. The position of the Magnetic Driven-Part is solved with iterative, root-finding techniques. The Magnetic-Joint may fail if the Circular-Profile and Irregular-Profile cannot stay in continuous contact for a complete machine-cycle. Wait, if you have many Magnetic-Joints in one model. See also:

### Video:

 How to... Add Magnetic-Joint