Spring FB

See Add Spring FB


Use a Spring FB to apply a force between two Points. The name we use for the two Points is Anchor-Points.


See also:

Machine Settings > Engineering Units

Configure Power Source


Edit the Spring FB

GA-Spring-Edit

In Mechanism-Editor:

1.Double-click the Spring-FB in the graphic-area

- or -


Spring dialog-box

Spring-Foce FB dialog-box

Spring Parameters 

Dialog-FB-SpringForce-SprPara

 

Check-box to enable the Spring FB.

Spring-Rate:

Spring-Force / linear unit difference (SI: N/mm) that the Anchor-Points deviate from the Free-Length. (see Force Units and Linear Units).


Free-Length:

Is the natural-length of the Spring, as it would be if it were not joined to the Anchor-Points.

If the distance between Anchor-Points > Free-Length, then the Force-Vector (due to the Spring-Rate only) will Pull Anchor-Points together (o>>>|<<<o)

If the distance between Anchor-Points < Free-Length, then the Force-Vector (due to the Spring-Rate only) will Push Anchor-Points apart (o<<<|>>>o)

If the distance between Anchor-Points = Free-Length, then the Force-Vector (due to the Spring-Rate only) = 0


Constant-Force:

A positive force will PULL Anchor-Points together (o>>> + <<<o)

A negative force will PUSH Anchor-Points apart (o<<< — >>>o)

Velocity Parameters 

Dialog-FB-SpringForce-VelPara

 

Coulomb Friction Force: (Ff = μ.Fn )
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 exactly Friction Force, because this force is not a function of the 'Normal Force'.

Note: Friction Force is not a Kinetostatic Force.


Viscous Coefficient: (Fv α V ( N/(mm/s) )

A Force that is proportional to the relative velocity between the Points.
The Force is opposite to the direction of motion.

E.g.: If the Damping Coefficient = 4 and the Velocity is +100mm/s, (anchor points moving away from each other’), then force pulling the points together is a force of 400N.


Drag Factor: (Fd α V2) ( N/((mm/s)2 ) )

A Force that is proportional to square of the relative velocity between the Points. For example, air resistance.

The Force is opposite to the direction of motion.

E.g. If the Drag Factor = 4, and the Velocity = +100mm/s (anchor-points moving away from each other’), then force pulling the points together is a force of 40000N.


Input-Connector and Output-Connectors


Note: It is not necessary to connect a wire to its input-connector or from its output-connectors. The connectors provide extra functionality.


Input-Connector

Connect a wire to the input-connector to add a force-function between the Spring's Anchor-Points.

The units of the data at the input-connector must be Newtons. Use a Maths FB to convert the data-type of a function to the Force data-type.

For example, the function might be designed as a motion. In which case, you would need to connect the output of a Motion FB , which has units of mm or degrees to a Math FB to convert the units to Newtons.


Note 1:

Units inside the Maths FB become SI units. To convert 100mm at the input to a Maths FB to 100N, you must:

1.Change the Output Data Type to Force (N)

AND

2.Multiply the input-value by 1000 to convert 0.1m to 100N

Note 2

To be consistent with the 'Constant-Force' Parameter:

A positive force at the input will tend to PULL Anchor-Points together (o>>> + <<<o)
A negative force at the input will tend to PUSH Anchor-Points apart (o<<< — >>>o)

TOP output-connector

Dimension, Velocity and Acceleration relating to the distance between the Spring's anchor-points.


Bottom output-connector

Total Applied-Force between the Spring's anchor-points.

oTotal Applied-Force = Force at the Input-connector + Force that results from the parameters as set in the Spring FB dialog-box

or

oDriving-Force = Linear Motive Force, if you configure the Spring FB as a Linear Motor - see Configure Power Source

Tutorials and Reference Help Files for MechDesigner and MotionDesigner 14.2 + © Machine, Cam, Mechanism, and Motion Design Software by PSMotion Ltd