More forward thinking manufacturers clearly realize the new role of increased safety on the factory floor as recent adopted international safety standards have shifted the way systems are evaluated.

Top management has already viewed Safety is a corporate responsibility, not an obstruction to daily production and it is essential to increased productivity and profitability.

As view, manufacturer has many demands of automation safeguarding and without proper safety design; the use of typical safeguarding devices often create undesirable production stop and reset delays when applied to contemporary manufacturing automation.  Motion robotics, pneumatics, hydraulics, and electromechanical systems often require safe and redundant machine stop to comply with regulations and consensus standards. 

Application strategies including creative use of muting allow for improved process restart and resumption of normal operation with minimized lost in production and excessive restart delays. 

Conflict between production requirements and safety often leave very little choice for designers to bypass or improperly apply safeguards in a manner not suitable to the level of risk posed by the automation.  Improper use of PLCs or switches to bypass safeguards is often applied even though this is prohibited by consensus standards universally.

Employing Fixed or Interlock barrier guard has been seen as a common approach to protect worker from machinery hazard. Although it is simple to construct to suit many different applications with minimal maintenance, it is sometimes not practical for changing production runs involving different size stock or feeding methods. Machine adjustment and repair often required guard removal that exposes danger to the maintenance personnel.

Therefore, presence sensing safety devices (PSSD) has been employed for high frequency entry and exit with ease of access, to improve cycle time compared to an interlocked door and ergonomic value.

Such PSSD products are available as Safety light Curtain, Presence sensing mat, or Safety Laser Scanner.

Safety Laser Scanner

Safety laser Scanner as a presence sensing safety devices are used for safeguarding dangerous areas and access points. Because they are so versatile, they can be used as a safeguard on both stationary and moving equipment.

One of the main benefits of the laser scanner is its versatility and non-intrusive presence. Unlike hard guards such as fences, the laser scanner works without physical barriers. Due to its sensing technology, it is perfect for equipment that regular maintenance and cleaning. Fewer hard guards are needed, allowing sweepers, forklifts, and loaders to transit through its protection area.

Safety Laser Scanner as a static application

In the above illustration, Safety laser scanner is used to protect operator from infringing the working area by creating 2 safety zones. A safety zone is programmed near to the working motion of the robot and scanner will send a stop signal to robot for any detection of human being and a warning zone is programmed for forklift loading area.

Presence Sensing Mat

These devices are used to guard floor area around a machine. A matrix of inter-connected mats is laid around the hazard area and the proper amount of pressure such as operator footstep will cause the mat control unit to send a stop a signal to the guarded machine.

Presence sensing mat are often used within an enclosed area containing several machines e.g. flexible manufacturing or robotics cells. When accessed is required into the cell they prevent dangerous motion if the operator strays from the safe area.

Safety Light Curtain

Safety light Curtains are extremely versatile and can guard areas many meters wide. When frequent access is required and physical guarding at the hazard is sometimes too restrictive, such PSSD is good to employ which prevents dangerous motion while allowing unrestricted access by sensing the presence of the operator and sending a stop signal. Resuming machine operation through Safety light curtain is also quick and efficient.

Safety light curtain is a safety system that complies with latest international standards and regulations. In fact, new Safety light curtain is able to comply with IEC61508, the international standard for functional safety.

As a safety system, it is equipped with safety diagnostic functions to determine its own safety health status and also the connected safety rated components.

Safety light curtain has many features to suit into different manufacturing conditions; and newly designed safety light curtain has combine safety and productivity with a no controller muting function.

Application Strategy - Muting

In safety application, employing presence sensing safety devices yield in few advantages and muting is one of the feature safety function when employ such devices.

Muting is to temporarily disables the light curtain when an object must pass through the detection zone, such as when supplying a workpiece to your equipment or when the machine cycle is in “non-hazardous” portion.

However, employing muting in any safety application required proper matching of hardware controller in the safety system that are standards compliance and effective muting is not reliable by adopting programmable controllers or bypassing interlock switches.

In the past, muting function required a dedicated “muting controller” but now it is built into the safety light curtain. The muting function is enabled simply by key cap insertion and muting sensor that determines the muting timing, as well as a muting lamp that communicates the muting status to other operator should be connected to the system as part of consensus standard.

Safety light curtain in muting mode employed in automatic packaging industries.

Correct usage of muting provides the following benefits;

1. No system shutdown between normal cycles.
2. Eliminates unnecessary components cycles – increased meantime between failure.
3. Provide safe integration per standards
4. Able to fail safe to a safe predictable state.

To boost safety applications without lower productivity, safety light curtain has been added with 2 new muting functions. “partial muting” which further heightens the level of safety, and “position detection muting” , which allows muting when the safety status can be determined by the position of a machine (such as a robot or in a press machine).

In the above illustration, partial muting raises safety by muting only the beams of the safety light curtain in the area where the workpiece passes through while prevents muting in all other areas. These give extra confidence to management that operators working on the production are safe and no truant can be play.

Complex Muting

Contemporary manufacturing process is complex and safety design can be expand to provide protection in a complex system with possibility of multiple muting on different process. Error status and maintenance log are also necessary for technician and engineers to troubleshoot the fault quickly and resume the production in the shortest possible time.

These can be achieved with the integration of Safety Network Controller to perform complicated safety functions.

Safety network controller has programmable safety circuits incorporated to facilitate efficient designing and modifications. Moreover, Safety I/O terminal can be added to increase safety I/O capacity for distributed allocation through the network. DeviceNet wiring on the existing network can be used as it, facilitating efficient design by expanding on the existingnetwork.

In the above illustration, Safety network controller is programmed with safety light curtain and muting position sensors are integrated as inputs are able to detect multiple positions or range of positions on a complex motion system as a result multiple safe position logic can be achieved.

Muting non-hazardous portion during machine cycle provide an economical means in prolonging life cycle of hardware as there are lesser stop cycles especially to hazard load switches in pneumatic, hydraulic and electro-mechanical. Adopting Muting as a safety functions has an added value functions in preventing accident and optimized safety that meet standards in the manufacturing process.

Safety is an integral part in manufacturing process, safety design is no longer a retrofit process that can be integrate at the end of whole machine design cycle, however, it is needed to seamlessly integrate right at the beginning of machine design. Such mindset will actually helps in cost saving.

When safety is integrated more tightly into the application, advance safety functions can be utilized optimally that helps to enhanced productivity rather than act as a guard function.