Module = P.C.D. ÷ Number-of-Teeth on Pinion

Rack/Pinion Ratio (degrees), per Rack Displacement (mm).

Read-Only

Rack/Pinion Ratio (deg/mm) - number of degrees the Pinion must rotate to move the Rack by 1mm.

Pitch Circle Diameter (mm) - the diameter of the Pitch Circle of the Pinion. We use the abbreviation P.C.D. most frequently.

P.C.D. (mm) =  Number-of-Teeth × Module

Pressure Angle: (Default = 20º).

The Pressure Angle of gears is usually 20º. Other standard Pressure-Angles are: 14º, 17.5º (weaker, quieter), 22.5º and 25º (stronger, noisier).

Addendum: (Usually = Module).

The height of the gear tooth from the Pitch-Circle to the tip of the tooth.

Dedendum: (Usually = Module * 1.25 (Module>1)).

The depth of the gear tooth below the Pitch-Circle to the root of the tooth.

The Dedendum is larger than the Addendum to give clearance for the tooth-tip of the two gears that engage with each other.

Root Radius: (Usually =  0.3 * Module)

The small fillet between the Flank and the Root of the Gear Tooth.

Points per Tooth Flank:

The number of points on each Involute of each gear tooth.  6 is OK. More points will make MechDesigner less responsive to each edit.

Note, these points are on the Involute. However, we draw lines between each Point on the Involute.

Shift the Rack by:

Move the rack along its pitch-line by # number-of-teeth.

Number-of-Teeth, Rack:

The number-of-teeth on the Rack.

Edit the Number-of-Teeth on the Rack so that it stays in mesh with the Pinion for a machine-cycle

# Number-of-Teeth, Pinion:

The number-of-teeth on the Pinion.

As you increase the number-of-teeth, the PCD increase, unless you also edit the Module.

Align Mesh:

When you add two(2) Racks to one(1) Pinion, you will usually see two(2) Pinions on the same axis. If you want to see one(1) Pinion, click one of these options:

◉Shift Rack

◉Shift Pinion

◉Do not Shift

Rack on the:

The positive-direction of Rack-Pinion and Ball-Screw model are specified when you select Right or Left.

◉Right (default)

When the Pinion (Ball-Screw Shaft) rotates Counter-Clockwise, the Rack (Ball-Screw Nut) move in the Positive-Direction of the Slide-Joint.

◉Left

When the Pinion (Ball-Screw Shaft) rotates Clockwise, the Rack (Ball-Screw Nut) move in the Negative-Direction of the Slide-Joint.

The symbol in the graphic-area of a Ball-Screw is a Helix/Screw.

There are two parameters:

•Ball-Screw Lead (mm) - distance the Sliding-Part moves after one(1) rotation of the Rotating-Part.

•Ball-Screw Diameter (mm) - diameter of the Ball-Screw symbol in the graphic-area.

The length of the Ball-Screw is equal to the length of the Line in the sliding-Part - see Add Rack-Pinion.

The Nut (Sliding-Part) of the Ball-Screw moves in the Positive-Direction of the Slide-Joint when the Rack-Side is set to Right - see General tab