Linear Rack and Pinion Drive

Rack

Usually a rectangular rigid component with uniformly distributed teeth on the side (matching the gear tooth profile), it can be fixedly installed or used as a moving part.

The materials are mostly high-strength steel (such as 45 grade steel and alloy steel), and the surface is quenched to improve wear resistance. In some scenarios, stainless steel or engineering plastics are used (for light load and corrosion resistance requirements).

Pinion gear

A small gear that meshes with the tooth profile of a rack is usually connected to the output shaft of a drive motor (such as a servo motor or stepper motor), and drives the rack to move (or move along the rack itself) through rotation.

The tooth profile design needs to match the rack (such as straight teeth and helical teeth), and helical teeth can reduce transmission impact and improve smoothness.

Auxiliary components

Guiding mechanism (such as linear guide rail, slider): ensures the straightness of motion and reduces the radial load on the rack/gear.

Drive unit: motor and reduction device (if speed or torque needs to be adjusted).

Lubrication system: grease or lubricating oil to reduce wear on the mating surface

Working principle

When the motor drives the pinion to rotate, the teeth of the pinion mesh with the teeth of the rack, converting the rotational motion into linear motion of the rack (when the rack is fixed, the pinion moves in a straight line along the rack).

The direction of motion is determined by the direction of gear rotation, and the speed is related to the gear speed and the number of teeth/tooth pitch of the gear (linear velocity=gear speed x tooth pitch).

Characteristics

Rack and Pinion Drive

Ball Screw

Synchronous Belt

Linear Motor

Maximum travel

Unlimited

≤ 6 meters

≤ 20 meters

≤ 10 meters

Maximum speed

10 m/s

2 m/s

5 m/s

20 m/s

Positioning accuracy

± 0.02~0.5 mm

± 0.005~0.05 mm

± 0.1~1 mm

± 0.001~0.01 mm

Load capacity

Ultra high (ton level)

high (≤ 5 tons),

medium (≤ 200kg),

low (≤ 100kg)

Maintenance costs

Low

medium

Low

high

Long stroke capability

The rack can be extended through splicing, easily achieving linear motion of several meters to tens of meters, without length limitations of transmission methods such as ball screws.

High load and rigidity

The contact area of the meshing surface is large, capable of withstanding high radial/axial loads, with good transmission rigidity, suitable for heavy-duty scenarios.

Speed advantage

It can achieve high linear speeds (usually 0.1-5m/s, some models can reach 10m/s or more) and respond quickly.

Simple structure

few components, low maintenance costs, strong tolerance to environmental factors such as dust and temperature.

Industrial automation

Machine tool worktable movement, truss robot handling.

Logistics warehousing

horizontal/vertical movement of stacker cranes, sorting line transportation.

Construction machinery

building elevators, gate opening and closing devices.

Automotive field

transplanting mechanism and steering system for automotive production lines (some models).

Model No

TMG170CM

TMG170CR

Motor Power (W)

750

Repeatability (mm)

±0.01/±0.02

Gear Teeth

32

Gear Pitch

5

Reduction Ratio

1:5

1:10

Lead (mm)

32

16

Max Speed(mm/s)

1600

800

Motor Speed 3000(rpm/min)

Max

Load

Acceleration Deceleration

Horizontal

0.3G

30

90

Vertical

0.3G

5

15

Rated Thrust

98

490

Linear guide (mm)

15*12.5-2

Origin Sensor

Out plug

EE-SX672(NPN-SX672P(PNP)

Inside

EE-SX674(NPN-SX674P(PNP)

Closed type

Open

Fully-closed

Accuracy is limited and there is a return error

The meshing clearance between gears and racks is difficult to completely eliminate (even with pre tensioning devices, there may be slight clearances), resulting in return errors during reverse motion. The positioning accuracy is usually between 0.1-0.5mm (high-precision models can reach 0.05mm, but the cost significantly increases), making it difficult to meet ultra precision scenarios (such as semiconductor wafer processing).

The operating noise is relatively high

The mechanical impact when gears and racks mesh will produce noise, especially at high speeds or under heavy loads; The helical tooth design can reduce noise, but it is still higher than transmission methods such as ball screws or linear motors, and is not suitable for environments with high noise requirements (such as medical equipment and laboratories).

High requirements for installation accuracy

The parallelism of the rack and the deviation of the center distance between gears will directly affect the meshing effect. If installed improperly, it can easily lead to increased wear on the tooth surface, unstable transmission, and even jamming, increasing maintenance costs in the later stage; Professional tools are required for calibration and installation (such as laser interferometer positioning).

Easy to be affected by pollution

The tooth surface is exposed to the outside (some models have protective covers, but this increases costs), which can easily absorb dust, debris, and other impurities, leading to poor meshing or scratches on the tooth surface. Additional dust-proof devices (such as retractable covers and blowing systems) need to be installed in dusty environments.

High dependence on lubrication

Tooth surface friction is sliding friction (rather than rolling friction). If lubrication is insufficient, it will accelerate tooth surface wear and heat generation, shorten service life, and require regular addition of specialized gear oil or grease. The maintenance cycle is more frequent than that of ball screws.