Linear Module vs. Electric Cylinder: Which One Do You Need?
Linear modules and electric cylinders (electric linear actuators with a push rod) often use the same ball screw and the same servo motor – yet they solve different tasks. The difference lies in how the load is guided. This guide explains when each design is the better choice.
Short answer
- Linear module: the load sits on a carriage running on integrated linear guides. Choose it when the axis must carry and guide a load – including side loads and moments – for example as an axis of a pick-and-place unit or Cartesian robot.
- Electric cylinder: a rod extends from a slim housing and pushes or pulls. Choose it for axial tasks where the load is guided elsewhere – pressing, lifting, clamping, positioning flaps or stops – and as an electric replacement for pneumatic or hydraulic cylinders.
Same drive, different construction
The two products below use a ball screw of the same diameter (Ø16 mm) and the same 400 W servo motor class. What differs is the mechanical design around it.
| Linear module – BSS140 | Electric cylinder – AC065 | |
|---|---|---|
| Output | Carriage on two linear guides | Push rod (with or without anti-rotation) |
| Ball screw | Ø16 mm, leads 5 / 10 / 20 / 32 mm | Ø16 mm, leads 5 / 10 / 20 mm |
| Stroke | 100–1050 mm | up to 1200 mm |
| Max. speed | up to 1600 mm/s | up to 1000 mm/s |
| Cross-section | 140 mm wide | 65 × 65 mm |
| Carries side loads and moments | Yes, via the guides (payload up to 110 kg horizontal) | No – the load must be guided externally |
| Axial force at 5 mm lead (400 W motor) | 1388 N rated thrust | about 1.4 kN (calculated); thrust bearing rated 5 kN |
The axial force is set by the motor and the lead (F = 2π · T · η / P), so with the same motor and screw both reach a similar value. The 5 kN figure of the AC065 refers to the capacity of its thrust bearing, which matters for pressing tasks with a larger motor or a gearbox.
When a linear module is the better choice
- The axis carries the load. Grippers, tools or parts sit directly on the carriage; the guides take up weight, side forces and moments.
- Load offset or overhang. A tool mounted off-centre creates moments that a push rod cannot accept.
- Multi-axis systems. Linear modules are the building blocks of gantry, cantilever and moving-arm systems.
- Very long or fast strokes with belt or rack-and-pinion drives.
When an electric cylinder is the better choice
- Pure push/pull tasks: pressing, joining, lifting, clamping, ejecting, adjusting stops or flaps.
- The load is already guided – by a slide, a hinge, a lever or the machine’s own guides.
- Little space across the axis: the slim square body fits where a 140 mm wide module does not.
- Replacing pneumatic or hydraulic cylinders: free positioning, programmable speed and force, no compressed-air leaks; front-flange or base mounting and rod ends with external or internal thread, rod-eye (spherical bearing) or trunnion make retrofits easier.
- Dirty environments: only the rod leaves the housing, while the screw stays inside.
Common mistakes
- Side loads on the rod. An electric cylinder is not a guide. Side forces or moments on the rod wear the bearings and the screw; add an external guide or use a linear module.
- Using a module only to push. If the load is guided anyway, a cylinder is usually more compact and economical.
- Forgetting anti-rotation. If the attached part must not rotate and is not otherwise held, choose the anti-rotation version of the cylinder.
- Vertical loads without a brake. Both designs need a brake motor when they hold a load vertically.
Selection checklist
- Is the load guided elsewhere? Yes → electric cylinder is possible. No → linear module.
- Are there side forces or an offset load? Yes → linear module (or cylinder plus external guide).
- Required axial force, speed and stroke → choose lead and motor (see How to size a linear module).
- Available space across the axis, mounting style (front flange or base) and rod end.
- Environment, anti-rotation and brake requirements.
Frequently asked questions
Is an electric cylinder the same as an electric linear actuator?
In industrial automation the terms are often used for the same product: a motor-driven ball screw that moves a push rod in and out of a housing. “Linear actuator” is sometimes also used more broadly for any motor-driven linear axis.
Can an electric cylinder replace a pneumatic cylinder?
Yes, in many cases. It offers free positioning and controlled speed and force. Check the required force and duty cycle, and plan the mounting and rod end so that no side loads act on the rod.
Can I add a guide to an electric cylinder?
Yes. With an external guide unit or a guided slide, a cylinder can handle moderate side loads; if the axis must carry larger loads or moments, a linear module is usually the simpler solution.
Not sure which one fits?
Send us the load, force, stroke, speed and a sketch of how the load is guided. We will recommend a linear module or an electric cylinder and send a drawing for review. Contact us or see all electric linear actuators and linear modules.
