Rack and Pinion / Ball-Screw

A Rack is a Linear-Gear. It engages with a Pinion, which is a Circular-Gear. The Rack-Pinion converts linear to angular motion, or rotary to linear motion. The Rack can drive, or be driven by, a Pinion. The linear motion of the Rack is proportional to the angular motion of the Pinion.

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


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

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.


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 with...

Use the Rack-Pinion dialog-box to edit the number-of-teeth on the pinion and along the rack, and to move the position of the rack along its axis.

You can edit the Gear Module plus other gearing parameters in the Rack-Pinion dialog-box.

You can also convert the Rack-Pinion to a Ball-Screw.

Preparation:

You must prepare two elements before you can use Add Rack-Pinion. The two elements are Lines [or CAD-Lines] in two different Parts. The two Lines must be joined with a Pin-Joint or a Slide-Joint.

Line 1: a child to a Part with a Green Part-Outline - the Driving-Part [also called Driving-Part].

Line 1: becomes the Pinion if it is a rotating-Part, or the Rack if it is a sliding-Part.

Line 2: a child to a Part with a Blue Part-Outline - the DriveN-Part

Line 2: becomes the Pinion if it is a rotating-Part, or the Rack if it is a sliding-Part.

Basic Rack and Pinion Models

Driving Pinion - DriveN Rack

Rack-Pinion1

Driving Pinion + Driven Rack.

Line1s-red in Part A, a Green Part-Outline, a rotating-Part, and will become the DriveR [Driving] Pinion.
Line2s in Part B, a Blue Part-Outline, a sliding-Part, and will become the DriveN Rack.

Note:

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

Add Rack-Pinion: command

Note the Line numbers: Lines1s-red2s. Each 'Line' is a Line or a CAD-Line.

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-Line1s-red in the Part with the Green Part-Outline, it is a kinematically-defined Part.
3.Click the CAD-Line2s in the Part with the Blue Part-Outline; it is NOT a kinematically-defined Part,
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 radius of the Pinion.
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

Driving Rack + DriveN Pinion.

Line1s-red in Part A, a Green Part-Outline. In this case, a the CAD-Line in the Slider, which becomes the DriveR [Driving] Rack.
Line2s in Part B, a Blue Part-Outline, 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

Note:

The Lines: 'Driving1s-red and Driven Part:2s. Each 'Line' is a Line OR a CAD-Line.

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-Line1s-red in the Part with the Green Part-Outline, it is a kinematically-defined Part.
3.Click the CAD-Line2s in the Part with the Blue Part-Outline; it is NOT a kinematically-defined Part,
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 radius of the Pinion, and to move the Rack along the Pitch Line, if needed.

CM-AddRackPinion-1

Rack-Pinion4

See also:

Kinematics-Tree, Pinion Driven Rack, Rack Driven Pinion, Dyads.

 

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