Denki Control Lab

Practical electrical control notes
Control Basics

What Is a Vacuum Ejector?

A vacuum ejector is a compact device that uses compressed air to create suction. In automation equipment, it is often used with a vacuum pad to pick up a workpiece.

  • It creates vacuum by using compressed air through an internal nozzle.
  • It works together with a vacuum pad, vacuum filter, and vacuum switch.
  • When suction is unstable, air pressure, leakage, pad condition, and filter clogging should be checked together.
See the basic flow Field check points

Good for

  • Beginners learning suction and pick-and-place equipment.
  • People who have seen a vacuum pad but are not sure where suction comes from.
  • Technicians checking why a workpiece is not being picked up reliably.

Not the focus here

  • Detailed model selection calculations.
  • Special vacuum systems for very large leaks or porous materials.
  • Deep product-specific parameter setting.

Quick answer

  • The ejector creates suction.
  • The pad touches the workpiece.
  • The vacuum switch confirms whether suction is strong enough.

In this guide

What it does Air and vacuum flow Senpai / kouhai note Vacuum switch role Field checks Official reference notes

What a vacuum ejector does

A vacuum ejector is the part that creates suction for vacuum handling.

In a simple pick-and-place system, the vacuum pad does not create vacuum by itself. The pad only touches the workpiece and seals against it. The vacuum ejector creates the negative pressure that makes the pad hold the workpiece.

In many factory machines, the ejector is used because it is compact, easy to mount near the pad, and can be controlled with a solenoid valve. When compressed air is supplied, the ejector creates suction. When the supply is turned off or release air is used, the workpiece can be released.

Overview of a vacuum ejector, vacuum pad, workpiece, and vacuum switch
Basic idea: the ejector creates vacuum, the pad holds the workpiece, and the vacuum switch confirms whether suction is strong enough.

Do not mix up the roles

The ejector creates vacuum. The pad contacts the workpiece. The vacuum switch checks the vacuum level. Thinking of these as separate roles makes troubleshooting much easier.

How compressed air becomes suction

The basic mechanism is simple: compressed air flows through the ejector, and vacuum is created at the suction port.

A common explanation is that an ejector uses the Venturi principle. Compressed air passes through a nozzle inside the ejector, the air speed changes, and a low-pressure area is created. This low-pressure area draws air from the vacuum side.

1. Supply air enters

Compressed air is supplied from the pneumatic line to the ejector.

2. Vacuum is created

The internal nozzle creates suction at the vacuum port.

3. Air is exhausted

Air from the vacuum side and supply air are discharged through the exhaust side.

Compressed air flow through a vacuum ejector and suction flow from the vacuum pad
In the field, it is useful to trace the system as supply air β†’ ejector β†’ vacuum line β†’ pad β†’ workpiece.

Practical note

If the supply air pressure is too low, the ejector may not reach the expected vacuum level. If there is a leak at the pad or tube, vacuum may drop even when the ejector itself is operating.

Senpai / kouhai conversation: where should I check first?

A short conversation can make the troubleshooting order easier to remember.

Senior technician character
Senpai

When suction is weak, do not start by replacing the ejector. First, check whether compressed air is actually reaching the ejector at the correct pressure.

Junior technician character
Kouhai

So the pad not picking up the part does not always mean the ejector is broken?

Senior technician pointing character
Senpai

Exactly. Check air pressure, tube connection, filter clogging, pad wear, workpiece leakage, and the vacuum switch setting as one chain.

How the vacuum switch fits into the system

The ejector creates suction, but the control system still needs a way to know whether suction succeeded.

That is where a vacuum switch is used. The vacuum switch monitors the vacuum level and sends a signal when the vacuum reaches the set level. In PLC control, this signal is often used as a suction confirmation input.

Vacuum ejector system with vacuum switch signal connected to a PLC input
The PLC does not directly know whether the part is attached. It usually checks a vacuum switch signal.

Control sequence example

Output ON to the ejector valve β†’ vacuum is generated β†’ pad holds the workpiece β†’ vacuum switch turns ON β†’ PLC allows the next movement.

If the vacuum switch setpoint is too strict, a normal pickup may be judged as failure. If the setpoint is too loose, the machine may think suction is OK even when the workpiece is not held safely.

Field check points when suction is unstable

Most suction problems should be checked as a system, not as a single part.

Air pressure

Check whether the supply pressure is within the expected range for the ejector and whether pressure drops during operation.

Tube and fitting leaks

Loose fittings, cracked tubes, or long narrow tubing can reduce the vacuum response.

Vacuum pad condition

Worn, hardened, dirty, or incorrectly sized pads can cause leakage at the workpiece surface.

Filter clogging

Dust or oil mist can clog the vacuum filter and reduce suction performance.

Workpiece shape

Porous, rough, curved, or uneven surfaces can leak air even if the ejector works correctly.

Vacuum switch setting

Confirm that the switch threshold and PLC input logic match the actual required pickup condition.

Field check points for a vacuum ejector suction problem
A practical check order: supply air β†’ valve operation β†’ ejector exhaust β†’ vacuum line β†’ filter β†’ pad β†’ workpiece β†’ vacuum switch signal.

Official reference notes used for this guide

This article keeps the explanation practical, but the technical points are based on official manufacturer information.

  • Schmalz explains vacuum ejectors as devices that work on the Venturi principle, where compressed air flows through a nozzle and vacuum is created at the vacuum connection.
  • SMC explains that vacuum generator selection involves suction flow, vacuum pressure, leakage, piping, and nozzle-related performance.
  • CKD product information shows ejectors that integrate vacuum generation and vacuum burst functions, which is useful for fast suction and release cycles.

Use the actual manual for real equipment

Set pressure, supply pressure, valve wiring, filter maintenance, and product limits depend on the actual model. Always check the official manual and the machine documentation before changing a setting.