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. The linear motion of the Rack is directly related to the angular motion of the Pinion.

A Ball-Screw is a device that converts rotary motion of a screw to linear motion of a nut.

You can use the Rack-Pinion dialog-box to convert a Rack-Pinion to a Ball-Screw.

To add the Ball-Screw, you must first add the Rack-Pinion. Then use the Rack-Pinion dialog-box to change the Rack-Pinion to a Ball-Screw.


Preparation:

You must prepare two elements before you can do Add Rack-Pinion. The two elements are Lines (or CAD-Lines) that are in two different Parts. The two Lines must be joined to a different Part with a Pin-Joint or a Slide-Joint.

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

The Driving-Part becomes 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 becomes 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

Rack-Pinion1

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.

Note:

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 axial with the Part that becomes the Rack.

Add Rack-Pinion

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

- or -

1.Click Machine element 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.


Note:

The Pinion may be 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.
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.

CM-AddRackPinion-1

Rack-Pinion2

Driving Rack - Driven-Pinion

Rack-Pinion3

PREPARATION: Driving Rack + Driven-Pinion.

LineRed-14-1 in a Green Part. In this case, a the CAD-Line in the Slider, which becomes the Driving-Rack.
LineRed-14-2 in a Blue Part, a rotating-Part, which becomes the Driven-Pinion.

Note:

The two Parts are joined to the same third Part. The third Part, in this example, is the Base-Part.
In this case, the Slide-Joint is axial with the Part that becomes the Rack.

Add Rack-Pinion: command

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

- or -

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

The Command-Manager now has two selection-boxes. You must select the two Line elements:

2.Click the CAD-LineRed-14-1 in the Part with the Green Part-Outline.
3.Click the CAD-LineRed-14-2 in the Part with the Blue Part-Outline.
4.Click OK-tiny-11-15 in the Command-Manager.

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

Note:

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 number of Gear-Teeth of the Pinion, the module of the Gears, and to move the Rack along the Pitch Line, if needed.

CM-AddRackPinion-1

Rack-Pinion4

 

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