Technical Information – TCG (Trochoid Cam Gear)

Comparison with Gears, Issues with Gears

What is a Rack and Pinion?

A rack and pinion is a type of gear that converts rotational force into linear motion. It is made of a small diameter circular gear called a pinion and a rack with teeth tracks cut into a flat bar. When rotational force is applied to the pinion, the rack moves horizontally to the end of the set gear tracks.

Conventional rack and pinion systems use involute teeth profiles. For this reason, the backlash is set from the design stage as a necessary condition for meshing. However, backlashes are avoided in equipment design for precision machinery because they cause stopping accuracy errors.

Backlashes also cause noise and vibration when the teeth mesh as well as slippage on the teeth surface of the meshing area, which can lead to premature wear.

  • Backlash (Deterioration of Stopping Accuracy)
  • Noise and vibration due to teeth rattling
  • Wear and dust generation in the meshing area
Backlash Illustration

What is a TCG (Trochoidal Cam Gear)?

A combination of a high-performance rack having a linear trochoidal tooth profile or a high-performance ring having a curved profile, and a pinion with a roller pin that rolls along the teeth, realizing rotational-to-linear motion by complete rolling.

It allows for Zero-Backlash, high-precision positioning, and light motion performance.

TCG - Trochoidal Cam Gear
TCG – Trochoidal Cam Gear

Structure of the TCG-Roller Pinion

The TCG Roller Pinion has a structure in which both rollers are supported by needle bearings to ensure smooth rolling.

The grease sealed in the bearing also removes the need for grease maintenance.

The shaft is frictionally fastened to the roller pinion via tightening the attached fastener, eliminating backlash at the fastened section.

Structural Diagram of Roller Pinion

Basic Principles of the TCG (Trochoidal Cam Gear)

Creation of Cycloid Curves

Creation of Cycloid Curves

A cycloid curve is a curve drawn by a point (P) when a circle rolls on a plane.

Creation of Theoretical Teeth Profile

Creation of Theoretical Teeth Profile

When multiple Ps are placed regularly on a circle, a regular cycloid curve and teeth pattern are formed on the plane.

Creation of Basic Teeth Profile

Formation of the Basic Teeth Profile

The basic teeth profile of TCG is the gear profile of the locus where the P is replaced by the roller pin.

Character and Merit of TCG – Trochoid Cam Gear


Trochoidal profiled tooth enables us to make a plurality of mutual teeth mesh at one time. The teeth always mesh via two or three portions and eliminate backlash when rotated in one or another direction.

Furthermore, since the roller of Roller pinion has a mechanism that rotates independently, it can be applied the preload (the pinion is pressed against the rack / ring), and it operates smoothly even when there is no backlash (clearance).

Meshing point
Meshing point

High Accuracy

Instead of gears, a combination of cam gear and roller pinion makes a positioning accuracy and feeding accuracy (rotation-linearity ratio) as nearly as that of the ball-screw structure.

The mechanism of TCG series that Non-backlash and precision operation are applied in various applications that require high accuracy, such as robots, loaders, and processing machines.

Items / TCG size 1010~4012
Premium grade Standard grade
Transmitting accuracy *1 (μm) ±30 ±50
Repetitive positioning accuracy *1 (μm) 10 20

*1: These values are for the measurement at the time of assembly under the temperature condition 20 ℃ and our specified mounting.It is affected by the mounting configuration, mounting accuracy and temperature etc.

Low noise

Rollers smoothly mesh with the optimized trochoidal tooth surface so as to avoid rattling noise, tooth striking noise and rotating noise from being induced together.

Low dust

Due to the smooth rotation, the structure dispenses with a least amount of heat and dust generated and cope with a clean room operation.

No need to maintenance for Lubricating grease

TCG series is Maintenance-free untill the rated life is achieved by applying grease only for the first time.
*Proven by our evaluation test.
(Please note that the grease life is affected by various conditions such as the usage environment.)

Clean room
Clean room

Extended length line and high speed driving – Cam Rack

Extendable with use of the connection jig “CJ”.

*We have the achievement of up to 74m.

Capable of high speed driving of 180 m/min or more.

Combination of Cam Rack and Ball Reducer with Roller Pinion
Combination of
Cam Rack and Ball Reducer with Roller Pinion

Circular arc ring and large-diameter ring – Cam Ring

The circular arc ring has been realized by the precision processing.Ring diameter up to tens of meters can be realized by combining the circular arc rings or can use only the necessary degrees.

Large Diameter Zero-Backlash Ring Gear
Cam Ring is realized
large-diameter and large-hollow by segmentation.

Please feel free to contact us for product information and technical consultation.

Kamo Seiko Corp.