Machine Design #11: Replacing a Pneumatic Cylinder with an Electric Cylinder – What to Check Before You Choose

In machine design, there is a question that comes up all the time:

Is a pneumatic cylinder fine for this mechanism, or should it be switched to an electric cylinder?

For simple motions such as pushing out, pulling back, stopping a workpiece, light lifting, light pressing, or opening and closing a cover, the pneumatic cylinder has long been the familiar choice.

Cheap. Easy to buy. Easy to mount. Maintenance staff are used to it. When something fails, you replace the valve, the sensor, or the cylinder, and it runs again.

But in recent years, in many automated machines — especially machines that need to change models, control position, speed or pressing force, or log production data — the electric cylinder is being used more.

One thing needs to be said clearly here.

"Going electric" is not automatically better. And using air is not automatically outdated.

There are places where an electric cylinder is well worth the money. There are places where a pneumatic cylinder is still the more sensible choice. And there are places where, if you choose wrong, cost rises quite a lot while the real-world benefit is barely any better.

This article records the points to keep in mind when comparing the pneumatic cylinder and the electric cylinder from a machine-design point of view.

Here I will refer collectively to types such as robot cylinders, electric cylinders, ele-cylinders and electric actuators as the electric cylinder, to keep things simple.

1. Can a pneumatic cylinder be replaced by an electric cylinder?

In principle, most motions that use a pneumatic cylinder can be replaced by an electric cylinder.

For example:

Pushing a workpiece out / pulling it in
Stopping a product
Lifting and lowering a small assembly
Positioning a mechanical unit
Light pressing
Gripping with an electric gripper
Rotating through an angle with an electric rotary actuator
Pushing a pin, pressing a bushing, light caulking

If the question is only "can it be replaced," then in most cases the answer is yes.

But in machine design, the more accurate question should be:

Is that replacement worth it?

Because when you go from air to electric, you do not just swap one cylinder. You change the whole way the mechanism is calculated and controlled.

With a pneumatic cylinder, in many cases you only need to pick the piston bore, the stroke and the air pressure, then adjust the speed on site with a speed controller. If the impact is strong, add a shock absorber. If it lacks force, increase the cylinder size or raise the pressure within the allowed range.

With an electric cylinder, you have to check more carefully:

How much load do you need to pull / push?
How much stroke is required?
What speed must be reached?
Is the acceleration / deceleration time appropriate?
Does the mechanism run horizontally or vertically?
Is a brake needed on power loss?
Do you need to stop at multiple positions?
Do you need to press with force?
Do you need to log position / force / result data?
Is there enough space for the motor, cabling and driver?
Have you counted the cost of the driver, controller, cables, IO or fieldbus?

In short:

A pneumatic cylinder is easy to use in a field-tuning style. An electric cylinder has to be calculated more carefully from the design stage.

2. Do not misread this as "you must drop all air"

There is a trend now that "the more electric, the better." It sounds right, but you have to be careful bringing it into machine design.

The pneumatic cylinder is still very strong for simple mechanisms.

For example:

Motion with only 2 points: out / in
No need to stop mid-stroke
No need to change position by model
No need for precise force control
No need to log data
Small space, a compact mechanism is needed
The factory already has an air system in place
Low equipment cost is required
Maintenance should stay simple and easy to replace

A simple workpiece stopper on a conveyor, an NG-product ejector, a cover that opens and closes, a temporary clamp — if there is no special requirement, air is still very reasonable.

The strength of air is that it is simple, cheap, easy to understand, easy to replace.

But in return, it is not strong on precise control.

Pneumatic cylinder speed is affected by pressure, flow, tube bore, tube length, valve condition, mechanism friction, changing load, and the on-site speed-controller adjustment.

A new machine runs smoothly. After some time, the cushion wears, the valve weakens, air leaks, workpieces vary in weight — and the speed starts to drift. Failures like this are not always easy to trace.

3. Where is the electric cylinder strong?

An electric cylinder is worth using when that motion affects:

Takt time
Assembly quality
Stability
The ability to change models
Inspection data
Long-term maintenance
Reduced manual on-site tuning

A few cases where an electric cylinder should be considered:

You need to stop at multiple positions
You need to change position by recipe
You need stable speed control
You need to reduce impact at the stop
You need to press with a relatively stable force
You need to know whether the end position was reached
You need to detect jamming, missing parts, or wrong pressing
You need to log force / position / OK-NG data
You need to reduce reliance on manual speed-controller tuning

Take, for example, a mechanism that pushes a product to several different positions depending on the model.

With air, you usually have to add stoppers, sensors, a manual adjustment mechanism, or combine several cylinders. The more models, the messier the mechanical side becomes.

With an electric cylinder, positions can be called by parameter or recipe. When the model changes, the machine moves to the new position on its own.

This is a very large advantage in assembly machines or inspection machines that handle many product types.

4. A key difference: air stops at a physical stop, electric stops at a coordinate

With a pneumatic cylinder, the basic motion is usually:

Extend to the end of the stroke
Retract to the end of the stroke
Stop against an external stopper
Stop by mechanical impact or by cushion

The pneumatic cylinder itself does not really know where it is. It only knows which side air is being supplied to.

To confirm position, you have to use a sensor. To stop mid-stroke, you have to add a stopper. To reduce impact, you have to tune the speed controller or add a shock absorber.

The electric cylinder, on the other hand, runs by coordinate.

For example:

Position 1: 20 mm
Position 2: 45 mm
Position 3: 70 mm
Wait position: 5 mm
Press position: 62 mm

That is, it has a notion of position from an origin. The designer can set position, speed, acceleration and thrust according to the mechanism and the program.

So the electric cylinder has a clear advantage in machines that need:

To stop at many points
To repeat stably
To change position by program
To reduce mechanical adjustment
To reduce setup time
To control motion by recipe

These are things a pneumatic cylinder can do, but usually only by adding many extra parts.

5. On speed and takt time: the electric cylinder is easier to calculate, but do not just pick blindly

With a pneumatic cylinder, the speed is usually tuned on site.

Too fast — tighten the speed controller. Too slow — open it up. Strong impact — slow the end of the stroke or add a shock absorber. Lacking force — review the pressure, cylinder bore and mechanism friction.

This is fast and easy to do, but a little "field-driven." That is, at the initial design stage, takt time is often only estimated. It only gets tuned to fit once the real machine is assembled.

With an electric cylinder, speed and acceleration must be calculated more clearly.

For example, if you need to travel 100 mm in 0.5 seconds, you cannot just look at the 100 mm stroke and pick a unit. You have to look at:

The maximum speed of the actuator
The allowed acceleration
The carried load
Whether the load is horizontal or vertical
The ball-screw lead
The motor power
The duty cycle
The rest time between runs
Whether the mechanism vibrates during acceleration / deceleration

An electric cylinder should not be "forced beyond its capacity" the way air is sometimes pushed. Choose wrong and the driver throws an alarm, the motor overloads, the screw wears quickly, or the mechanism vibrates.

But if chosen correctly, takt time becomes far easier to control. The motion runs stably, impact is reduced, and it depends much less on manual tuning.

6. Mounting space: do not just compare the cylinder body

Many people looking at catalogs will see that an electric cylinder is bigger than a pneumatic one.

This is true if you only compare the main body.

An electric cylinder has a motor, an encoder, cabling, sometimes a brake. On top of that, it needs a driver or controller. So if you only look at a single actuator unit, it usually feels larger and more expensive.

But when it goes into the real machine, you must compare the whole assembly.

With a pneumatic cylinder, you usually have to add:

A solenoid valve
A speed controller
Air tubing
Fittings
Stroke sensors
A mechanical stopper
A shock absorber
A pressure regulator
Space for the operator to adjust the valve
The routing of the air tube as the unit moves

Especially if the mechanism needs a soft stop or high speed, the cushioning and stopper parts can take up a fair amount of space.

Meanwhile, the electric cylinder — although the body is larger — comes in many layout forms:

Motor in line with the axis
Motor folded in parallel
Motor turned to the left / right
Cable exit in various directions
Rod type
Slider type
Slide-table type
Belt type for long stroke
Mini type for small loads

So when comparing space, do not conclude from the catalog picture alone.

Place it in the real machine layout and look at the whole thing: the actuator body, the motor, the cables, the driver, the stopper, the sensor, the tubing, and the maintenance-access area.

7. On force: do not just take the air thrust and look for an "equivalent" electric type

A very common mistake when swapping air for electric is to take the thrust of the pneumatic cylinder and then look for an electric cylinder with roughly the same force.

That is not enough.

With a pneumatic cylinder, theoretical force is usually calculated as:

Force = pressure × piston area

But the real force is also affected by friction, pressure loss, seal condition, travel speed and safety factor.

With an electric cylinder, you have to look further at:

Maximum thrust
Continuous thrust
The speed at that force level
Mounting orientation
The carried load
Acceleration / deceleration
The ball-screw lead
The motor power
Whether there is a brake
The life of the screw and the guide
The duty cycle

An electric actuator can produce large force at low speed, but when it runs fast the available force can drop. Conversely, if you pick an oversized actuator just to be "safe," cost rises unnecessarily.

This point is very important.

When replacing, do not just ask: How much force did the old cylinder have?

Instead ask again: How much force does the mechanism really need, at what speed, under what conditions?

8. Ball screw, belt, servo, pulse motor: choose wrong and cost balloons

The electric cylinder comes in many configurations. Not every type is the same.

The most common are:

Motor + ball screw
Motor + timing belt
Servo motor
Pulse motor / stepper motor
Multi-position type
Simple 2-point type
Type with force control
Type with a load cell

For the ball-screw type, the lead of the screw directly affects force and speed.

A small lead is usually favorable for large thrust, slower and more precise motion. A large lead is favorable for speed, but thrust drops with the same motor.

The belt type usually suits long stroke and higher speed, but its stiffness and ability to take pressing force differ from the ball screw.

In addition, servo and pulse motors also differ a lot in cost.

A servo is usually strong on feedback, speed, stability and controllability. But it costs more.

A pulse motor, or the simpler ele-cylinder lines, can be enough for 2-point or a few basic positions, at lower cost and easier to use.

So if you only need to replace a simple air cylinder that goes out / in, picking a multi-axis, multi-position, fully-optioned servo right away can be overkill.

Conversely, if you need to control force, speed, many positions and data, choosing a type that is too simple will leave you short on function later.

Good design is choosing just enough — not choosing by feel.

9. Going electric is not only linear cylinders: grippers, rotary and slides can also be replaced

These days it is not only linear cylinders that can go electric.

The following mechanisms also have electric versions:

Air gripper → electric gripper
Rotary cylinder → electric rotary actuator
Pneumatic slide table → electric slide
Air cylinder rod type → electric rod actuator
Pneumatic pressing mechanism → electric press / servo press

The electric gripper

The air gripper has the advantage of being simple, high-force and easy to use.

But the electric gripper has the edge when you need to:

Adjust the gripping force
Adjust the stroke
Grip many product types
Check whether the product was actually gripped
Reduce impact when gripping
Store or read the gripping state

However, when choosing an electric gripper you still have to look at the gripping-force chart. For many gripper types, the gripping force changes with the distance from the grip center to the actual grip point. This is the same as the air gripper, and must not be skipped.

Many gripper-selection errors come from looking only at the nominal gripping force, while forgetting that the further you grip from the center, the larger the moment and the lower the actual force.

The electric rotary

With a pneumatic rotary cylinder, in many cases the mechanism rotates to the end point and stops against a cushion.

When switching to an electric rotary, you have to look much more carefully at the inertia of the load.

You need to check:

The mass of the rotating assembly
The distance from the center of rotation to the center of gravity
The moment of inertia
The rotation angle
The rotation time
Acceleration / deceleration
Vibration at the stop
Off-center load
Cables, tubes or anything dragged along during rotation

Put simply, with an electric rotary you cannot just ask "is the torque enough?" You have to look at how fast that load rotates, how it accelerates, and whether it vibrates at the stop.

10. Pressing, press-fit, caulking: the electric cylinder has a very clear advantage

For operations such as pressing a pin, pressing a bushing, caulking, or pushing a part into position, the pneumatic cylinder can still do the job.

But if you need to control the quality of the pressing process, the electric cylinder or servo press has a much bigger advantage.

With air, you usually only know:

Whether the cylinder reached the end of the stroke
Whether the end-of-stroke sensor is ON
Whether the pressure is sufficient

But it is hard to know precisely whether the pressing process happened correctly.

For example:

Did the pin go in correctly?
Did it jam halfway?
Was it pressed too deep?
Is a part missing?
Is the pressing force within limits?
Is the final position correct?

With an electric actuator that has a push mode or a load cell, you can control much better:

The pressing force
The pressing position
The pressing speed
The judgment threshold
The force–position curve
The OK / NG result

For example, when pressing a pin, you can set conditions such as:

If the force rises too early → the pin may be misaligned or jammed
If the force does not rise → the pin may be missing or the hole too large
If the final position is not reached → pressing is not deep enough
If the force exceeds the limit → there is a risk of damaging the product

This is a very strong point of going electric.

It is not just "push and be done," but using the pushing process itself to inspect quality.

Some actuators even allow several pressing-force levels within one stroke. For example, within a 50 mm stroke you can set several pressing zones or several different push conditions if the controller supports it.

This is something air can do, but it becomes much more complex if you want to manage the detail.

11. Vertical use requires more care

For a vertically mounted mechanism, the electric cylinder is usable, but should not be chosen the same way as a horizontal one.

You need to check:

Will the load fall on power loss?
Is a brake needed?
Does the motor have enough holding force?
Is the screw self-locking?
Will it sag when stopped for a long time?
Does the vertical load shorten the life?
Is the mounting orientation allowed by the manufacturer?
Does the lubricant behave well when mounted vertically over the long term?

One small but worthwhile point: with some actuator types, when mounted vertically for a long time, the motor orientation and the lubricant condition should be checked against the manufacturer's recommendation. In some cases it is better to place the motor at the top to avoid the risk of grease flowing toward the motor unit over the long term.

It is not that vertical mounting is forbidden. But vertical mounting must be checked more carefully.

Especially for lifting mechanisms that carry a load, if power is lost and the load falls, it is not just a machine fault but a safety problem.

12. Cost: the electric cylinder is more expensive, but the total cost is not necessarily higher

If you only compare purchase price, the electric cylinder is usually more expensive than the pneumatic one.

But when you count the whole assembly, you have to add many things.

For air:

The cylinder
The solenoid valve
The speed controller
Air tubing
Fittings
Sensors
Stoppers
Shock absorbers
The pressure regulator
Leak maintenance
Speed-tuning time
Shock-absorber replacement time
The compressor and its energy loss

For electric:

The actuator
The driver / controller
The motor cable
The encoder cable
The power supply
IO or fieldbus
Parameter-setup time
Replacement cost on failure
The requirement for electrical / control maintenance skills

If there is just one simple out / in motion, air is usually cheaper.

But if that mechanism has to change position by model, be tuned repeatedly, cause machine stops, or directly affect product defects, the electric cylinder can be cheaper over the machine's life.

Especially in machines with many product models, setup time and errors from manual tuning can sometimes cost far more than the initial price gap of the actuator.

13. A quick way to check before deciding to replace

When you want to replace a pneumatic cylinder with an electric one, I think you should check in this order.

1. What task does the current motion perform?

Pushing, pulling, lifting, pressing, gripping, rotating or positioning?

If it is just a simple out / in, going electric may not be needed.

2. Do you need multiple positions?

If you need multiple positions, the electric cylinder has the advantage.

If there are only the 2 end points, air is still very strong.

3. What is the real load?

Not just the workpiece mass. You have to include the jig, the plate, the guide, friction, dragged cables and off-center load if any.

4. How much speed and takt time do you need?

Do not just write "run fast." You need numbers.

For example: 100 mm stroke, run in 0.6 seconds, stop for 0.2 seconds, 20 cycles per minute.

5. Do you need force control?

If it is just a light touch, air may be enough. If you need force / position judgment, look at electric.

6. Is the mechanism horizontal or vertical?

Vertical mounting means you must look at brake, load holding, power loss, life and safety.

7. Is there enough space?

You have to look at the motor, cables, driver, cable bend radius, maintenance area and the removal / mounting direction.

8. Is the control system suitable?

Does the PLC have enough IO? Do you use EtherCAT, CC-Link, EtherNet/IP, Modbus, or just simple IO? Can the maintenance staff handle parameters and alarms?

9. Is the total cost reasonable?

Not just the cylinder price. Compare the whole: valves, cables, tubing, stoppers, shock absorbers, driver, installation time, tuning time and later maintenance.

14. A few cases where you should keep air

Switching to electric is not always the better move.

Keep air if:

The motion is very simple
No need to stop at many positions
No large impact on quality
No data needed
Space is very tight
Cost is strongly limited
The environment has a lot of dust, oil, heat and vibration, and electrical maintenance is hard
The factory has standardized on pneumatic spare parts
The operators and maintenance staff are used to the air system

The simpler a mechanism is, the more carefully going electric must be weighed.

There are positions where the pneumatic cylinder is good enough. Forcing it to electric only makes the machine more expensive and harder to maintain.

15. A few cases where you should seriously consider an electric cylinder

Consider an electric cylinder if:

You need to change position by model
You need multiple stop points
You need stable speed
You need to reduce impact
You need controlled pressing force
You need to detect faults during the pressing / pushing process
You need to log production data
You need to reduce manual tuning
You need to calculate takt time clearly from the design
You need to raise machine quality over the long term

Especially for mechanisms involving inspection, precise assembly, pin pressing, product positioning, or feeding many models, the electric cylinder is well worth considering.

Conclusion

The pneumatic cylinder and the electric cylinder are not absolutely one better than the other.

The pneumatic cylinder is strong in simplicity, low cost, easy mounting, easy replacement, and it fits ordinary two-point motions very well.

The electric cylinder is strong in controlling position, speed, acceleration, force and data, and in the ability to change models by program.

When you replace a pneumatic cylinder with an electric one, do not just take the old cylinder's thrust and stroke and look for an equivalent part number.

You need to look again at the whole set of working conditions:

What task is the mechanism performing?
How much force is needed?
How much speed is needed?
Is the load horizontal or vertical?
Do you need multiple positions?
Do you need force control?
Do you need OK / NG data?
Is there enough space for the motor and cables?
Are the PLC and the maintenance staff a good fit?
Is the total life-cycle cost worth it?

Going electric is not about making the machine look more modern.

Going electric is only worth it when it makes the machine more stable, easier to control, with less manual tuning, fewer faults, and better service in real operation.

But if the motion is simply out / in, does not affect quality much, needs no data and no multiple positions, then the pneumatic cylinder is still a very practical choice.

In machine design, choosing right is not choosing the more expensive item. Choosing right is choosing the mechanism that is just enough for its real task.

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