Electric cylinders and linear actuatorsSizing and comparison with pneumatic and hydraulic cylinders

Electric cylinders and electric axes: when to choose them

A linear motion on a machine can be achieved with three technologies: pneumatic, electric and hydraulic. Interfluid distributes all three (Pneumax for pneumatics, Pneumax and AutomationWare for electric, Atos for hydraulics). This lets us advise you without a built-in preference: we assess axis by axis which technology fits best, based on force, accuracy, energy use and total cost.

Our technical department supports you in sizing, in choosing between an electric cylinder and an electric axis, and in assessing when a pneumatic or hydraulic cylinder can be replaced by an electric solution.

Electric cylinder or electric axis: the difference

• Electric cylinder (rod-type linear actuator): a rod pushes and pulls the load, like a pneumatic or hydraulic cylinder. The motor drives a ball screw. Pneumax 1800 series cylinders have ISO 15552 mounting interfaces, so they can replace a pneumatic cylinder with limited mechanical changes.
• Electric axis (linear system): a carriage runs along a guided profile, driven by a belt or a screw. It is the solution for long strokes, high speeds and multi-axis Cartesian systems (XYZ), such as pick & place gantries.

Pneumatic, electric or hydraulic: the comparison

Rule of thumb: pneumatics for simple moves between two positions, electric when you need intermediate positions, control and data, hydraulics when you need very high forces in little space or shock resistance. On many machines the best solution is hybrid.

How to choose: the questions to ask for each machine axis

When an electric cylinder replaces a hydraulic cylinder

Until a few years ago electric actuators were limited to low and medium forces. Today AutomationWare Mech electric cylinders exceed 200 kN of thrust, and the Mech Extreme version, with reinforced steel structure and ISO 5 ground screw, reaches 700 kN dynamic load. In this range the electric cylinder becomes a real alternative to hydraulics:

• it removes the power unit, piping and oil filtration;
• it eliminates the risk of leaks, which matters in clean environments;
• it uses energy only while working;
• it provides accurate positioning and force control without proportional valves.

Hydraulics remains the right choice for very high forces in compact spaces, shock loads and heavy-duty applications. In these cases we offer Atos hydraulic cylinders and servo cylinders, up to 320 bar, also with position transducer for closed-loop control.

How to size an electric axis

To propose the right solution we need the following data:

1. Load and force: mass to move or thrust required, and how it varies along the stroke.
2. Stroke: usable length of the motion.
3. Speed and acceleration, and the cycle time to meet.
4. Accuracy: required positioning repeatability.
5. Duty cycle: number of cycles, shifts, dwell times under load.
6. Orientation: horizontal, vertical (with motor brake if needed) or inclined.
7. Environment: dust, wash-down, temperature, protection rating.
8. Control: PLC and communication protocol, motor already specified or to be supplied.

With these data we choose the transmission: belt for long strokes and high speeds (up to 3 m/s, typical repeatability ±0.05 mm), ball screw for higher thrust and accuracy (typical repeatability ±0.01 mm). We then define size, gearbox and motor.

The range: Pneumax and AutomationWare electric cylinders and axes

The full features of each series are described above on this page and in the downloadable catalogues.

Further reading

• Electric axes vs pneumatics: when to switch
• Electric axes vs pneumatic cylinders: selection guide for machine builders
• Pneumatic cylinders and hydraulic cylinders

Application examples

Two typical situations in which we propose that machine builders switch to electric, and what changes in practice.

From pneumatic to electric: pick & place on a pharmaceutical blister machine

The situation. The pick & place module of a blister machine uses pneumatic cylinders to pick and place the product. At every format change the operator moves the end stops and adjusts the flow controls: the machine stands still for tens of minutes and the first cycles produce scrap. Air exhausts are also an issue in a controlled-contamination area.

The solution. AutomationWare electric axes in a Cartesian layout, with AW Drives connected to the PLC. The positions for each format are stored as recipes. Simple ejection movements stay pneumatic: a hybrid solution.

What changes.

• format change drops from tens of minutes to a few minutes, by recalling the recipe from the operator panel;
• no air exhausts in the product area, and less noise;
• much lower compressed air consumption: in documented packaging cases, replacing the most air-hungry actuators cut air consumption by more than 30%;
• position and force of every axis available for predictive maintenance.

From hydraulic to electric: punching and forming of sheet metal parts

The situation. A punching and forming station for sheet metal parts (for example brake components) runs on a hydraulic cylinder with a dedicated power unit. The power unit runs for the whole shift, oil leaks onto the line and the force varies with oil temperature: some parts must be re-checked or scrapped.

The solution. An AutomationWare Mech series electric cylinder, sized on the force actually needed along the stroke, with force and position control and the force-stroke curve recorded at every cycle. The power unit, piping and oil management are removed.

What changes.

• repeatable force, independent of temperature, with fewer parts to re-check;
• traceability of every part through the stored force-stroke curve;
• lower energy use: an electric servo drive works at efficiencies around 80%, against the 40-50% typical of a hydraulic circuit, and draws power only during the stroke;
• zero leaks, no oil or filter changes, floor space freed at the line.

The critical point is sizing: the required force is not simply the old cylinder's pressure times area, but the real force profile along the stroke. This is where our technical department comes in.

Electric cylinders and axes: frequently asked questions

What is the difference between an electric cylinder and an electric axis?

An electric cylinder has a rod that pushes and pulls like a pneumatic cylinder and can use the same ISO 15552 mounting interfaces. An electric axis moves a carriage along a profile, driven by a belt or a screw, and suits long strokes and multi-axis Cartesian systems.

When should a pneumatic cylinder be replaced by an electric axis?

When you need intermediate positions, software format changes, speed and acceleration control, process data for Industry 4.0 or lower compressed air consumption. For simple moves between two fixed positions the pneumatic cylinder often remains the most economical choice.

Can an electric cylinder replace a hydraulic cylinder?

Yes, when force and duty cycle are within its range: AutomationWare Mech electric cylinders exceed 200 kN and the Extreme version reaches 700 kN dynamic load. The power unit, piping and the risk of oil leaks are eliminated. For very high forces in compact spaces or shock loads, hydraulics generally remains the better solution.

What do you need to size an electric axis?

Load or required force, stroke, speed and acceleration, positioning accuracy, duty cycle, orientation (horizontal or vertical), working environment and control system. With these data our engineers select transmission, size and motor.

Belt or ball screw electric axis?

Belt drives suit long strokes and high speeds (up to 3 m/s on Pneumax 18T axes, typical repeatability ±0.05 mm). Ball screw drives offer higher thrust and accuracy (typical repeatability ±0.01 mm) over shorter strokes.

Are the electric axes compatible with my PLC?

AutomationWare AW Drives support ModBus RTU, CANopen CiA 402, EtherCAT, PROFINET RT and IRT, and include the STO safety function.

Why Interfluid

• Three technologies, one partner: pneumatic, electric and hydraulic, for a neutral choice axis by axis.
• Official Pneumax distributors, with the AutomationWare mechatronic range.
• Sizing support from our technical department, from the first analysis to motor and drive selection.
• Experience on machine builders' equipment: we also design and build pneumatic control panels, useful in hybrid solutions.

Need to size an electric axis?

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