Light Curtain or AI Camera? Comparing Press Machine Safety
A detailed comparison of light curtains and AI camera safety systems for press machines. Hand detection, muting challenges, and bypass risks analyzed.
Press Safety: Light Curtain vs. AI Camera — Which Is More Effective?
Press machines carry the highest limb loss risk in industrial production. Hand entrapment accidents in eccentric and hydraulic presses affect thousands of workers annually. The light curtain has been the standard solution for years, and AI camera safety systems now add a complementary layer on top of it.
What Is a Safety Light Curtain?
A safety light curtain is an optoelectronic protective device that stops a machine when any part of a person enters its protected field. A transmitter and a receiver are mounted on either side of the hazardous opening and form a grid of infrared beams; when an object interrupts a beam, the curtain's safety outputs switch off within milliseconds and the machine control stops the hazardous motion. It is one of several safeguarding devices covered in our guide to machine guarding types and methods.
Safety light curtains are rated under IEC 61496 (Type 2 or Type 4) and are integrated to a required performance level under ISO 13849 or IEC 62061. Their resolution — finger, hand or body detection — and their response time determine how far from the hazard they must be mounted.
Light Curtain: Proven But Limited
How It Works
A light curtain creates an infrared beam array between a transmitter and receiver positioned in front of the press die area. Any object breaking the beam immediately stops the press.
Advantages
- Decades of field experience and proven reliability
- Type 4 models achieve SIL3/PLe safety levels
- Fast response time
- Wide range of brands and models (SICK, Leuze, Keyence, Omron)
Disadvantages
Muting problem: Light curtains cannot differentiate objects — material passage triggers false stops. This necessitates muting (temporary bypass). Misconfigured muting creates serious safety gaps.
Bypass risk: Light curtain bypassing is a widespread and dangerous problem. Operators may disable light curtains to increase production speed. This is among the leading factors in the most severe accidents.
Single-line protection: Light curtains only protect along a vertical line. They provide no protection when the operator approaches from the sides or below.
Mounting distance: The mounting distance calculated per ISO 13855 may require placement far from the press, negatively affecting production ergonomics.
Light Curtain Safety Relay Basics
A light curtain does not stop the press on its own: its two safety outputs (OSSDs) feed a safety relay or a safety PLC, which removes power from the press control circuit. The safety relay monitors both channels, so a single wiring fault or a stuck contact is detected instead of silently disabling protection, and it requires a deliberate reset before the press can run again.
This safety chain — curtain, safety relay or safety PLC, press control — is what carries the curtain's certified safety rating. Any additional device, including an AI camera, is wired in alongside this chain as an extra input; it does not take its place.
AI Camera Press Safety System: The Next-Generation Approach
How It Works
The AI camera system uses deep learning models to detect the press operator's hand, arm, and body in real time through camera imagery. When approach to the danger zone is detected, the press is immediately stopped.
Advantages
Hand-material differentiation: AI solves the light curtain's biggest problem through shape-based detection. It doesn't produce false alarms during material passage, eliminating the need for muting.
Cannot be bypassed: Since there's no physical beam, it cannot be physically bypassed. The camera-based system records bypass attempts.
Wide area protection: A single camera can monitor the operator's front, sides, and approach angles. It provides multi-directional protection that light curtains cannot.
Multi-function: Press safety, PPE detection, zone monitoring can be achieved on the same camera platform. No separate devices needed for each function.
Easy retrofit: ISEE-CAM mounts on existing presses without structural machine modifications. It connects to safety relays or PLCs via dry contact outputs.
Real-World Scenario: The Muting Problem
At an automotive supplier factory with 20 eccentric press lines, light curtains require constant muting adjustments and operators widen muting windows under production pressure.
With an AI camera system, this problem disappears entirely: since the system visually distinguishes hands from material, the muting concept becomes unnecessary. Production speed is maintained while safety levels increase.
Decision Matrix
| Criterion | Light Curtain | AI Camera |
|---|---|---|
| Hand-material differentiation | No (muting needed) | Yes |
| Bypass risk | High | Very low |
| Protection area | Single line | Wide area |
| Multi-function | No | Yes |
| Retrofit ease | Medium | High |
| SIL/PL certification | Type 4 (SIL3/PLe) | Not safety-rated — adds a layer alongside certified devices |
Conclusion
The light curtain remains a valid solution with its proven reliability. However, muting issues, bypass risks, and single-line protection limitations can create serious safety gaps.
AI camera press safety systems like ISEE-CAM are a strong additional layer, especially for facilities experiencing muting problems, high bypass risk, and multi-function needs. Used together with a certified light curtain and its safety relay, they create a layered safety architecture.
ISEE Vision offers free site surveys for press safety, providing customized solution proposals for your facility.