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Safeguarding a machine at the point where material is positioned and a process is performed, is known as point-of-operation safeguarding. The goal of point-of-operation safeguarding is to prevent the operator from being exposed to a hazardous motion when the machine is in operation. Point-of-operation safeguarding is an important concern wherever processes such as shearing, punching, welding, forming or assembly are being performed and there must be interaction between workers and machine.
SICK safety light curtains not only keep workers safe from the hazardous motion(s) of machinery, but they can also improve productivity. Opto-electronic safeguarding devices can reduce access time by potentially eliminating the need for mechanical safeguarding devices.
Considerations for using a safety light curtain, or any other safeguarding device, for point-of-operation safeguarding, are outlined in ANSI B11.19. “A presence sensing device shall prevent the operator or others from reasonably reaching over, around, under or through the sensing field into the hazardous area.” Auxiliary safeguarding may be required in conjunction with the safeguarding device to accomplish this requirement.
“A safety light curtain shall be installed so that access to a hazardous motion or zone cannot occur without being detected and a stop signal is generated. In addition, personnel must always be detected if they are present within a hazardous zone.”
Point-of-operation safety light curtains typically fall into two “Type” classifications: Type 2 and Type 4. These designations correspond to the Category requirements outlined in EN954 and UL 61496. |
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Advanced Light Curtain Applications for Machine Tool
Muting: Muting can be defined as the temporary suspension of the safety circuit by a self-checking control reliable, redundant control system during the normal operation of a machine. The muting circuit can only be active when the machine is a non-hazardous portion of its machine cycle. Muting must be control reliable.
Blanking: Blanking is the ability to open a “window” in the light curtain to allow objects such as an automatic feeder or table top to penetrate through the light curtain. It is useful for objects that will always remain present and in the same position. Floating blanking is for objects that are not stationary, such as materials in a press brake.
Presence Sensing Device Initiation (PSDI): With PSDI, an operator can easily remove a workpiece from the machine: breaking the light beam stops the machine and the operator does not need to wait for a mechanical gate to rise. The operator can position a new piece, and once the operator clears the light curtain, the machine switches on and runs through its next cycle (refer to applicable machine standards for guidance on use). PSDI replaces mechanical controls, reducing repetitive motion injuries and access time for operators.
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Safety Categories A Type 4 application is one in which a potential injury could be severe (normally irreversible and usually permanent), workers are exposed frequently, or for prolonged periods, to a hazard and there is low possibility of avoiding the hazard. Most applications in Machine Tool are Type 4 applications, including:
- Hydraulic and Mechanical
- Presses
- Press Brakes
- Punches
- Filter Presses
- Welding and Assembly
- Shears
SICK has a complete family of Type 4 Point-of-Operation safeguarding products: the C4000 family of Safety Light Curtains. The C4000 safeguards workers in automated production areas and optimizes work processes. It can be used vertically, horizontally or diagonally for safeguarding areas with potential hazards to personnel or equipment. With its flexible design to fit all applications, the C4000 is simple to commission, maintain and easy to use. The C4000 offers the ability to implement all advanced functions for safeguarding complex machinery. Some of the highlights of the C4000 include:
- Flexibility. There is a C4000 system for every application, from simple to advanced.
- Simplified machine integration and lower wiring cost. There is no need for additional safety relay modules.
- Advanced functions, self-diagnostics and E-stop and reset controls all integrated into the light curtain.
- Universal interface. Every C4000 Safety Light Curtain works with all interface and control architectures: from relay and safe PLC control to safety fieldbus.
- Nearly maintenance-free operation.
- IP 65 robust, high integrity housing.
- Flexible mounting.
- Recessed window with ridges for protection from damage by tools or material
- High weld-flash and strobe light immunity
- Fastest Response Time in the industry
- 14, 20, 30 and 40 mm resolution
The C4000 can be mounted in a variety of configurations to provide ease of access, material placement, material removal and maintenance without compromising the safety of workers. The C4000’s small dimensions and high resolution allows it to be installed closer to the hazardous zone and operate with a smaller safety distance. The C4000 can also be configured to accommodate various advanced functions of safeguarding through the use of the LCU-P interface controller. These functions include muting, reset, external device monitoring, cascadability, blanking and PSDI. |
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Type 2 applications are those in which the potential injury would be slight (normally reversible), exposure to the hazard is short or infrequent, and the hazard is possible to avoid under specific conditions. An example of a Type 2 application would be on a pick and place machine where the injury sustained might only be a bruise or a pinched finger.
SICK offers the C2000 for Type 2 applications.
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