Spring-Force Function-Block dialog-box

Use the Spring-Force FB to apply a force between two Points.

Edit the Spring-Force FB to edit the Spring-Force FB parameters.

Notes: Spring FB Input-Connector and Output-Connectors

A Spring FB has one input-connector and two output-connectors.

You do not need to connect wires to the input or from its output-connectors.

Input-Connector: no connection needed. If connected, then the data must be Force Units. Use a Maths FB to convert any other unit to Force units [N]. Connect any Forcing Function to its input.
Top Output-Connector: always reports Position, Velocity and Acceleration relating to the distance between the Spring's anchor-points.
Bottom Output-Connector: always reports applied or driving Force between the Spring's anchor-points.

The Force that is reported is the Applied-Force or the Driving-Force between the Spring's anchor-points:

oApplied Force = Force at the Input-connector + Force that results the Spring and Velocity Parameters as set in its dialog-box - see parameters, below
oDriving Force =Linear Motive Force, if the Spring has been configured as a Linear Motor - see Configure Power Source

See: Machine Settings > Engineering Units

See: Add Spring-Force FB, Configure Power Source


Spring Parameters 


Enable Spring Force check-box.

The Force [in Force Units] exerted by the Spring for each Linear Unit [in Linear Units] difference between the Free-Length and the actual distance between the Spring's Anchor-Points.


At this length, the Spring will exert a force between the Points equal to the Constant Force, which may be zero.


A Positive value will pull Points together.

A Negative value will push Points apart.

Velocity Parameters 


Coulomb Friction Force: (Ff = μ.F)
A Constant Force that is opposite to the direction of the motion.

This parameter is intended to be similar to a Friction Force.

However, it is NOT Friction Force, because this Coulomb Friction-Force is not a function of the 'Normal Force'.
Note: MechDesigner cannot model Friction Force since that is not a Kinetostatic Force.

Viscous Coefficient: (Fv α V)
A Force that is proportional to the relative velocity between the Points.
The Force is opposite to the direction of motion.
Drag Factor: (Fd α V2)
A Force that is proportional to relative velocity, squared.
For example, air resistance.
The Force is opposite to the direction of motion.

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