Forming Constraints

The forming constraints forming condition is a constraint put on the displacement (movement) of a node or group of nodes.  This prescribed displacement can be used to stop rigid body notion, to define symmetry in half or quarter models or to control material movement in the model.

The most basic form of prescribed displacement is to control the degrees of freedom of a node, that is, its translation in the X, Y, & Z direction and its rotation about the X, Y, & Z axes.

The movement of a node can also be constrained in a direction that is not aligned with the X, Y, & Z axes, this is called Constrained Movement.

To apply forming constraints to your part, select the Forming Constraints option under the Forming Conditions icon. 

To apply forming constraints you first select the type of entity that you would like to constrain using the appropriate selection filter (line, hole, point, or edge) followed by defining the constraint to be applied, either Displacements or Constrained Movement.

Constrained Movement & Normal To Edge Forming Constraints

Select the appropriate checkbox to define the direction of prescribed displacement, in the x, y and/or z direction or about the x, y and/or z direction. A prescribed displacement of 0 will fix the movement of the selected nodes in the defined direction. A purple line will indicate the direction of constraint.

To constrain the movement in a direction not aligned with the major axes, turn on the Constrained Movement checkbox and specify the direction and distance of the prescribed displacement in the Direction and Distance fields. A displacement of 0 will fix the movement of a node in the specified direction, but allow movement in the normal direction. A purple line will indicate the direction of constraint.

There is a third form of Forming Constraints available in FASTFORM Advanced that applies to edge nodes only where the motion of the node is set to a prescribed displacement normal to the edge of the model. The Normal to Edge prescribed displacement is a special case of the other two types of Forming Constraints.

To set movement of nodes normal to the edge of the model, turn on the Normal to Edge checkbox and specify the normal displacement in the Distance field. The edge nodes will be fixed to the specified distance normal to the edge of the model, but will be allowed to move in the direction along the edge of the model. To completely fix a node to a position the specified distance normal to the edge of the model, turn on the Fully Constrained Movement checkbox.

NOTE:  For a FASTFORM Advanced analysis the nodes are only allowed to move in the x and y direction, all other degrees of freedoms are ignored. For a Springback analysis, all degrees of freedom are available.

Forming Constraints (FC) can be applied to edges, holes, lines (on surface or mesh), points (on surface or mesh). All these geometry entities are converted to nodes, and during solving all constraints are applied to nodes.

To create FC, click the "Forming Conditions" icon on the forming workbench toolbar , and select "Forming Constraints". The dialog will appear and:

• All previous selected entities will be unselected
• The Select Edge button checked and the selection filter automatically set to select edge.
• All controls should be set to 0, the type of constraints set to displacements, boxes for Xt and Yt are checked, and the OK button is disabled. You may change the type of constraints to "Constrained movement" or "Normal to edge"

During Selection:

• The FC is not displayed on the part with the selected entities.
• Selection will be the same as with regular selection (i.e. with ctrl key for multiple selection)
• As soon as one entity is selected, the OK button is enabled.

At this point, you can start to edit the FC parameters by entering values.

During Editing:

• The Select Edge/Line/Hole/Point buttons will automatically be unchecked, turning the selection off.
• All other interdependent controls will update automatically, along with the FC display.
• If you wish to continue selection of geometry entities, click on one of the filter buttons and continue selection.