Mechanism | Add Rack-Pinion - Ball-Screw

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Mechanism | Add Rack-Pinion - Ball-Screw

Rack and Pinion / Ball-Screw

See also Rack-Pinion dialog-box

A Rack is a Linear-Gear that engages with a Pinion, which is a Circular-Gear.

The Rack-Pinion pair converts linear to angular motion, or rotary to linear motion.

A Ball-Screw (& Nut) pair is also a device that converts rotary motion of a screw to linear motion of a nut, or converts linear motion of a nut to rotary motion of the screw.  

Use the Rack-Pinion dialog-box to convert a Rack-Pinion to a Ball-Screw.


Before you can do Add Rack-Pinion. you need a model that has a:

Part that is kinematically-defined  - it is a sliding-Part or a rotating-Part.

Part that is NOT kinematically-defined - it is a rotating-Part or a sliding-Part.

After you do Add Rack-Pinion, the two Parts are kinematically-defined (Green Parts).

To do Add Rack-Pinion, you select a Line in the two Parts.

Line 1: a child to a Green Part - the Driving-Part.

The Driving-Part becomes (will be) the Pinion if it is a rotating-Part, or the Rack if it is a sliding-Part

Line 2: a child to a Blue Part - the Driven-Part.

The Driven-Part is a Green Part after you do Add Rack-Pinion.

The Driven-Part will be the Rack if it is a sliding-Part, or the Pinion if it is a rotating-Part.

Add Rack-Pinion / Ball-Screw

Add Rack-Pinion Ball-Screw icon

Machine Elements toolbar : Add Rack-Pinion (Ball-Screw)

Menu :

Add menu > Mechanism sub-menu > Add Rack-Pinion (Ball-Screw)

Edit Rack-Pinion :

Rack-Pinion dialog-box

If required, use this dialog-box to convert the Rack-Pinion to a Ball-Screw.

Rack and Pinion

Driving-Pinion - Driven Rack


PREPARATION: Driving-Pinion + Driven Rack.

LineRed-14-1 in Part A, a Green Part, rotating-Part - it will become the Driving-Pinion.

LineRed-14-2 in Part B, a Blue Part-Outline, sliding-Part - it will become the Driven Rack.


The two Parts are joined to the same third Part. The third Part is the Base-Part.

It is not necessary that the Slide-Joint is radial from the Pin-Joint.

Add Rack-Pinion

1.Click Add menu > Mechanism sub-menu > Add Rack-Pinion / Ball-Screw

- or -

1.Click Machine elements toolbar > Add Rack-Pinion / Ball-Screw

The Command-Manager has two selection-boxes.

Select the two Line elements:

2.Click the CAD-LineRed-14-1b in the Green Part, that is kinematically-defined.

3.Click the CAD-LineRed-14-2 in the Blue Part; that is NOT kinematically-defined,

4.Click OK-tiny-11-15 in the Command-Manager

The Rack-Pinion is in the Assembly-Tree and Graphic-Area.


The Pinion may be very, very small!

The Rack is parallel to the CAD-Line in the Sliding-Part. It is offset by the Pitch-Circle Radius of the Pinion.

Use the Rack-Pinion dialog-box to edit the radius of the Pinion. e.g: edit the Module parameters, or number of teeth.

If you close the model and open it at a later time, you may need to use 'Rebuild' to regenerate the symbols for the Rack-Pinion.




Add Rack-Pinion


Driven Rack