Inside a Linear Module: Components and Their Functions Explained

1. Overview: what lives inside a linear module?

A modern linear module can be divided into a few main groups:

Base and cover structure – the “frame” that supports everything

Guiding system – keeps motion straight and carries the load

Drive system – turns rotary motion into linear motion

Carriage (slider) – the moving platform that connects to your tooling

Motor and coupling interface – connects the actuator to a motor

Sensors and cable routing – for homing, limits and wiring

Seals, strips and lubrication – for protection and long life

Let’s open the module and look at each group in more detail.

2. Base and cover: the structural backbone

2.1 Base profile

The base is usually an aluminum or steel extrusion or machined profile. Its tasks:

Provide a straight reference for the guides and screw

Carry loads from the carriage into the machine frame

Offer a pattern of mounting holes and slots

Key design points:

Stiffness: a deeper or thicker profile resists bending and torsion better, which improves accuracy and vibration behavior.

Flatness: the mounting surface must be machined or extruded accurately; otherwise, the guides can bind.

Mounting features: T-slots, drilled holes or dowel holes help you align the axis in your machine.

In heavy-duty ball screw modules the base may be made of steel for higher rigidity; in light, high-speed modules, aluminum is common to reduce mass.

2.2 Top cover or strip

On many modules, the base is closed by a top cover or a stainless-steel strip:

Protects the screw and guides from dust, chips and coolant

Gives the module a flat top surface for mounting brackets

Can be fixed or moving (in the case of a sliding cover or strip)

In fully enclosed modules, the cover design is one of the most important elements, because it directly affects how well the module survives harsh environments.

3. Guiding system: rails, blocks and support

Even the best drive system will not perform well without a proper guide. In most linear stage parts, guidance is provided by linear guides.

3.1 Linear guide rails

Inside the base you will typically find one or two linear guide rails, fixed with bolts along their length.

They:

Define the straight line along which the carriage moves

Take radial and moment loads caused by the payload

Keep the carriage from rotating or tilting

The rail material and heat treatment give it hardness and wear resistance. Straightness of the rail and accuracy of its mounting surface directly influence the linear module’s running accuracy.

3.2 Guide blocks (carriages)

Each rail has one or more guide blocks (also called carriages or sliders). The moving platform of the linear module is bolted to these blocks. Their role:

Recirculating balls carry the load with low friction

Distribute forces into the rail

Provide smooth, repeatable motion along the axis

In compact modules you often see two blocks on a single rail; in heavy-load modules there may be two rails and four blocks to increase moment capacity.

4. Drive system: the heart of the ball screw module structure

For a ball screw linear module, the drive system converts motor rotation into linear travel.

4.1 Ball screw

The ball screw is a precision-machined screw shaft running the length of the axis. It:

Transfers torque from the motor to the linear motion

Defines the mechanical resolution through its lead (mm per revolution)

Works with the nut to generate thrust

Important parameters:

Lead – a small lead gives higher thrust and finer resolution, but lower maximum speed; a large lead gives higher speed but less mechanical advantage.

Diameter – larger diameter increases stiffness and critical speed, allowing longer stroke or higher RPM.

Precision grade – determines pitch error and, together with preload, the positioning accuracy of the module.

4.2 Ball nut

The ball nut is mounted on the module carriage. Inside it:

Balls circulate in tracks between screw and nut

Rolling contact minimises friction compared to a plain screw

Preload can be applied to remove backlash

When the screw rotates, the nut translates along the screw, carrying the carriage, guide blocks and your payload.

4.3 Screw supports and bearings

At one or both ends of the module, you find support housings with bearings:

The fixed end usually has a pair of angular-contact bearings or a bearing set capable of taking axial and radial loads.

The support end can have a single radial bearing to support the screw but allow expansion from thermal growth.

Their functions:

Keep the screw aligned with the guides

Control axial play

Define the screw’s natural frequency and allowable speed

Good alignment between screw and guides is essential; otherwise, the nut and bearings can wear prematurely.

5. Carriage: the moving platform

The carriage (also called the slider or table) is the visible moving part of the module.

5.1 Mechanical role

It:

Connects directly to the guide blocks

Holds the ball nut

Provides mounting holes and reference surfaces for your tooling, gripper or fixture

Because it must transfer all forces from the payload into the guides and screw, its design needs sufficient stiffness. Larger carriages spread loads over a wider footprint and improve moment capacity.

5.2 Features on the carriage

You will often see:

Threaded holes and dowel pin holes for attaching brackets or plates

Grooves or locating edges that serve as references during assembly

In enclosed modules, connection points for cover strips or bellows

6. Motor and coupling interface

The module does not move unless you connect a motor.

6.1 Motor bracket or flange

At one end of the base, there is a motor mounting flange or bracket:

Matches standard servo or stepper motor dimensions (for example, 60 mm, 80 mm)

Aligns the motor shaft with the screw shaft

Provides precise geometry for easy bolting and dowelling

Many suppliers offer different motor adapter plates so you can mount motors from various brands without redesigning the module.

6.2 Coupling

Between the motor shaft and screw shaft, a coupling is installed:

Transmits torque

Compensates small misalignments between shafts

Reduces shock and vibration

Common types include flexible jaw couplings and bellows couplings. The correct choice depends on speed, torque and how sensitive your application is to torsional wind-up.

6.3 Optional gearbox

In some applications, a gearbox is added between motor and coupling:

Increases available torque

Improves resolution at the cost of speed

Helps size a smaller motor for a heavy axis

The motor interface on the module must be strong and accurately machined to support the gearbox weight and preserve alignment.

7. Sensors, switches and cable routing

To integrate a linear module into a control system, you need position references and safe stops.

7.1 Home and limit sensors

Most modules include slots or tapped holes for:

Home sensor – gives a repeatable reference position when the axis powers up

End-of-stroke limit sensors – stop the motion safely at each end before hitting mechanical stops

Sensors can be inductive, optical or magnetic. Cables usually run in small channels along the base or inside external drag chains.

7.2 Hard stops

Mechanical end stops are often built into the base or bolted on:

Act as a last line of defence if the controller fails to stop the axis

Help protect the screw, nut and guides from crashing beyond their design range

They are not meant for everyday use, but they can prevent catastrophic damage.

7.3 Cable management

To avoid cable fatigue and interference:

Many modules include cable anchors at the carriage and base

External axes often use a cable carrier or drag chain, guided by brackets attached to the module

Clean routing of motor, sensor and tool cables is an important part of building a reliable system.

8. Seals, lubrication and protection

Even the best mechanical design will not last without proper lubrication and protection.

8.1 Seals and wipers

Guide blocks and ball nuts typically have end seals and side seals:

Keep grease in the rolling elements

Reduce entry of dust, chips and coolant

In harsher environments, the module may use:

Stainless-steel cover strips

Bellows or telescopic covers

Additional scrapers on the carriage

8.2 Lubrication system

Lubrication points are provided for:

Linear guides – via nipples or integrated ports on the blocks

Ball screw – via a greasing port on the nut or a central lubrication manifold

In some modules, a single lubrication port feeds both screw and guides. For high-duty cycles or hard-to-access installations, connection to an automatic lubricator is recommended.

8.3 Why this matters

Good sealing and lubrication:

Extend service life and maintain accuracy

Reduce noise and stick-slip

Lower the risk of unexpected stoppages during production

When comparing modules, pay attention not only to load charts and stroke options but also to how easy it is to lubricate and protect the internal parts.

9. Putting it all together

When you assemble all these linear module components, you get a compact axis that:

Keeps motion straight via the guides

Provides thrust and resolution via the ball screw and nut

Supports everything on a stiff base and carriage

Connects directly to your motor and control system

Uses sensors, seals and lubrication to stay reliable over millions of cycles

Understanding this internal architecture helps you:

Read cross-section drawings of ball screw module structure

Ask precise questions when working with suppliers

Identify whether a problem is likely due to guides, screw, support bearings, motor interface or protection