Industrial optical sorting relies on a rapid sequence between the optical detection of a product (using sensors, cameras, or spectrometers) and its targeted ejection if it does not meet compliance criteria.
In this very high-speed process — sometimes involving several hundred ejections per second — performance does not depend solely on detection quality. It largely relies on the speed, repeatability, and power of the air jet generated by the solenoid valve. This is where MAC Valves technology makes the difference.
Thanks to their exceptional response times, extended service life, and ability to maintain consistent performance in harsh environments, MAC solenoid valves ensure more precise, faster, and more reliable sorting.
Ultra-short response times
For high-speed sorting operations
High-precision ejection
For reliable and efficient sorting
Millions of cycles
Outstanding reliability and durability
Intensive industrial applications
Designed for demanding environments
The Three Main Types of Optical Sorting
MAC Valves technology is used in several types of optical sorting systems, each adapted to a specific product type or production line configuration: air jet sorting, pusher/paddle sorting, and free-fall sorting.
Air-Jet Sorting
Products are conveyed flat on a belt, pass in front of an optical sensor, then are sorted using an air jet expelled through a nozzle controlled by a solenoid valve.
Typical applications:
Recycling (plastics, paper, bottles)
Food industry (flat, dry products)
Sorting of industrial parts.
Technical features:
Blow from below, above, or both sides
Valves synchronized by detection
In-line valve bars
Pusher or Paddle Sorting
A product detected as non-compliant is physically pushed off the line using a pneumatic cylinder (controlled by a solenoid valve) or a rotary system.
Typical applications:
Food industry (fruits and vegetables, potatoes, tomatoes, citrus, etc.).
Particularities :
Suitable for unstable or rolling products
Controlled ejection force
Reduced risk of product damage
Technical features:
Requires a fast, consistent solenoid valve (dedicated MAC Valves ranges).
Free-Fall Sorting
Products fall in free fall in front of a camera. When a product must be ejected, a vertical air jet is triggered via a nozzle controlled by a solenoid valve.
Typical applications:
Food industry (rice, grains, coffee, lentils, pellets, seeds, etc.).
Particularities :
No conveyor required
Very high precision in flow
Suited to high speeds for small, light, fast-moving products.
Technical features:
64 to 320 channels in parallel
Direct control from the optical controller
Compact, high-frequency solenoid valves.
Free-Fall Sorting
Products fall in free fall in front of a camera. When a product must be ejected, a vertical air jet is triggered via a nozzle controlled by a solenoid valve.
Typical applications:
Food industry (rice, grains, coffee, lentils, pellets, seeds, etc.).
Particularities :
No conveyor required
Very high precision in flow
Suited to high speeds for small, light, fast-moving products.
Technical features:
64 to 320 channels in parallel
Direct control from the optical controller
Compact, high-frequency solenoid valves.
How Do Solenoid Valves Work?
In an optical sorting system, air jet quality does not depend solely on valve mechanics. The electrical signal controlling the solenoid valve is equally critical. It affects valve opening speed, cycle repeatability, coil heat generation, and signal stability at high frequency.
Square-wave signal (24 VDC)
The solenoid valve receives a square electrical signal at 24 VDC. The maximum on-time (coil energization time) may be limited depending on coil power.
Easy to use.
No cable length limitation.
On-time + reduced holding voltage/current
The valve is driven by a square signal (e.g., 24 VDC) for a defined time to open. A lower holding voltage is then applied (e.g., 10 VDC) to keep it open, reducing energy while maintaining the active state.
No cable-length limitations
Faster de-energize time
Optimized power consumption
Less coil heating
Pilotage par temps d'activation et maintien par PWM* (Pulse Width Modulation)
The valve receives a square signal (e.g., 24 VDC) for a defined time to open. A PWM signal is then applied to hold the valve, modulating delivered power to keep the state with reduced energy.
Single power supply required
Reduced de-energize time
Lower energy use
Less coil heating
PWM control via three-wire circuit
The PWM signal can also be delivered via a three-wire connection between the PLC and the valve. In this setup, the circuit handles power/current directly, while the PLC provides only the command signal (not the load power).
PLC does not source the current
PLC outputs only the trigger
Faster de-energize time
Reduced de-energize time
Less coil heating
MAC Valves Solenoid Valves for Optical Sorting
The patented Bullet Valve®, featuring MAC’s latest technology, uses a specific design that guarantees extremely precise response times and flow rates. The Bullet Valve® flow is factory-set during assembly to your application by simply adjusting the poppet stroke.
Adjusting the stroke between the permanent magnet and the poppet in the coil also improves valve-to-valve repeatability of response times.
These two essential MAC characteristics are checked on every valve at end-of-line (not by sampling), enabling production of valves with identical response times and flow rates.
1- Bullet Valves® — Series BV210, BV214, BV221
- Ultra-fast response times
- Extremely high repeatability
- Low friction
- Long service life
- Virtually zero dead volume
Bullet Valves® Séries BV210DD, BV221DD
- Very short response times
- Silent operation
- High flow rate in a compact design
- Ideal for variable pressure
- Customizable
Solenoid Valves for Air Jet Sorting – Series 34, 52, 72
- High flow in a small footprint
- Designed for high-frequency operation
- Maximum reliability and repeatability
- Ultra-fast 3/2 valves
Solenoid Valve for Ejection Paddle Sorting - Series 400
- Powerful 5/2 control
- Controlled ejection force
- Extremely high reliability
- Long service life
Optional Use of PWM Technology
MAC Valves optionally uses this technology to save energy and/or protect the coil during long hold-signal phases.
PWM can be integrated into your control electronics, into the control lead, or directly on the valve coil.
Easy installation
No overheating
Exceptional repeatability
High-frequency compatible
Impact of the signal on performance:
- Energize time
- De-energize time
- Pressure rise time at the nozzle
- Consistency of the air jet
A poorly defined drive signal can cause:
- Less accurate sorting
- Excess energy consumption
- Premature valve wear
“Net Impact Force” (NIF): Measuring the Ejection Force of Your Sorting System
In high-throughput optical sorting, the air-jet power determines whether the targeted object is correctly ejected. But this power isn’t just a theoretical pressure or flow value: it is measured at the nozzle, at the exact moment the solenoid valve is activated. This is what MAC Valves calls Net Impact Force (NIF).
NIF is a standardized measurement of the air blast impact force produced at the nozzle outlet, expressed in grams or newtons.
NIF is measured using a piezometric dynamic force sensor, an oscilloscope, or a standardized nozzle.
Optimizing Optical Sorting via Pneumatic Circuit Design
The channel connecting the valve outlet to the nozzle should be:
-As short as possible
-Of constant diameter
-Free from turbulence
This ensures laminar flow, minimal pressure loss, and improved air jet consistency.
The nozzle design influences:
-Jet shape
-Jet concentration
-Jet range
Pressure response
Choosing the Valve Type: Axial or Radial
Axial Flow Solenoid Valves (MAC Valves Bullet Valve®)
Lower pressure loss
Faster response times
Ideal for compact circuits
Phases de l'impact du jet d'air
T0
Mechanical response time
Time between the start of the electrical signal and the start of mechanical opening of the solenoid valve.
T1
Pressure Build-Up
Filling of the circuit until the blow-off threshold is reached.
T2
Actual Impact
Onset of the mechanical ejection force acting on the target object.
T3
Deactivation
Time between cutting the electrical signal and the start of mechanical closing of the solenoid valve.
T4
End of ejection impact
End of the ejection force acting on the object.
T5
Purge
End of purging of the ejection circuit.
