About Specifying a Mechanism's Nominal Position

When you create an assembly, you are defining the original—or nominal—configuration of the model. For mechanisms, the nominal configuration is based on the engineering connections of the model: the values assigned to controlled constraints in an engineering connection determine the relative distance or angle between two components of the model. The nominal distance or angle between two components appears in the Value column of the Engineering Connection box.

When you simulate a mechanism, you modify the values of the controlled constraints. To decide whether the changes must be permanent, select one of the following Apply to Nominal options in the Assembly App Options panel:

• Transient Mode: The changes to the controlled constraints are not permanent. The mechanism returns to its original configuration when you finish reviewing the simulation.
• Nominal Mode: The changes to the controlled constraints are permanent. The configuration of the mechanism at the end of the simulation becomes the new nominal configuration of the model, under certain conditions.

Select the mode in the Mechanism Player box. If you select the Nominal Mode, perform an Update to associate the new controlled constraint values to the corresponding engineering connections.

Important: The PLM Update process updates the entire product and takes into account: The changes made to the controlled constraints The synchronization of other contextual links affecting the configuration (position and shape) of the product's components involved in the mechanism. For more information on the PLM Update, see Update.

After the update, you can modify the configuration of the model's components according to certain conditions. The nominal mode behavior of the submechanism depends on the following factors, illustrated in the table below:

• The number of instances of the submechanism.
• The product flexibility, also known as the Positional Mechanical Reference (PMR) Product.
• The valuation of the controlled parameter of the engineering connection.
  Note: In the Engineering Connection box, do not fill in the Value column. This value determines the initial configuration of the mechanism.

  For more information, see Mechanical Systems Design User's Guide: Creating Engineering Connections for Mechanisms.

Root Product	Before Simulation	Last Simulated Position in the Mechanism Player	After Closing the Mechanism Player	After the PLM Update
Case 1: an instance of a submechanism
			After both commands, the simulated position of the parts is saved. The Nominal Mode is applied: the new configuration of the mechanism is saved as the permanent configuration of the model.
Case 2: n instances of a submechanism a flexible product commands with no values
			After both commands, the parts' simulated position is different and maintained. When several instances of the same mechanism can be animated, their position is kept only if the current mechanism contains a flexible product without controlled constraints. The instances keep a different position, with respect to the father.
Case 3: n instances of a submechanism product not flexible		The instances move in different directions.
			After both commands, the parts move back to their initial position. If a product is not flexible, the nominal position is not applied. Note: if the parts have the same simulated position with respect to the father product, then the simulated position is kept, like in Case 5.
Case 4: n instances of a submechanism a flexible product commands with values			The parts' simulated position is maintained.	The parts move to have all the instances at the same positions.
			If you did not specify values for the constraints, the position of a single instance is kept, while the others align to the same position.
Case 5: n instances of a submechanism product not flexible		The instances of the submechanism are in the same direction.
			After both commands, the parts' simulated position is maintained if it is the same, with respect to the father.

Important: If you have one instance of a submechanismmechanism, the nominal mode is applied. To keep the same configuration when you have several instances of a sub- (see Case 2): Add flexibility to your product. Do not specify values for the engineering connections associated with the command.