Safety is Pilz's core competitive advantage. Centered on the core concept of "safe motion," Pilz has launched a complete set of safe and efficient servo drive solutions, encompassing motion control systems, servo amplifiers, and servo motors.
Unveiling the mystery of safety intermittent operation
Jogging is a type of motor control method, often used for rapid movement of machine tool tool posts, beams, columns, etc., and for machine tool tool setting. The general steps of jogging control are: pressing the jogging button -- the contactor coil conducts -- the main contacts close -- the motor is energized and starts running; when the jogging button is released -- the contactor coil is de-energized -- the main contacts open -- the motor loses power and stops.
Because this control circuit lacks self-locking and is not connected to other automatic devices, the main circuit is only energized when the start button is pressed, and de-energized when the start button is released. The most typical example is the control of a traveling vehicle. The contactor itself does not have mechanical self-locking; so-called self-locking is achieved through the circuit. A typical jog operation involves energizing the contactor coil via a button, causing the contactor to engage; releasing the button de-energizes the coil, and the contactor disengages.
Pilz integrates the safety control card PMCprotegoS into the servo amplifier PMCprotegeD, which can be expanded with various safety functions, including all safety aspects (such as STO, SS1, SS2, SOS, SLS, SSR, etc.), helping users reduce installation time and maintenance workload, and improve productivity. Thanks to features such as Safety Speed Limiting (SLS) and Safety Stop Functions (STO/SS1/SS2), the equipment can be safely jogged even when the protective devices are open.
Traditional jogging vs. Safe jogging
Traditional jog operation
The operator switches the equipment to jog mode, presses the jog button, and a part or all of the equipment runs at a low speed. Releasing the jog button stops the equipment. This control method is commonly used for controlling the lifting motor of electric hoists and the motor control for the rapid traversal of lathe pallet boxes.
The inching forward control circuit consists of a changeover switch, a fuse, a start button, a contactor, and a motor. The changeover switch serves as a power isolation switch, the fuse provides short-circuit protection, the start button controls the energization and de-energization of the contactor coil, and the main contacts of the contactor control the start and stop of the motor.
Safe inching operation
The operator switches the equipment to safe jog mode and presses the jog button. A part or all of the equipment runs at a low speed, and the safety monitoring unit monitors the safe speed. Releasing the jog button activates the safety stop function, and the equipment comes to a safe stop.
In automatic operation mode, the safety speed monitor tracks the axis's stopping status. Only when the axis has stopped can the operator open the safety door and enter the machining area. In manual adjustment mode, the safety speed monitor tracks the axis's operating speed. Operators or adjustment personnel can open the safety door and operate the machine using the enable button and jog switch. If the speed exceeds the safety setpoint, the speed monitoring module responds immediately, and the main module outputs a safe stop signal according to the programmed sequence.
A typical safety jog application structure is shown in the figure below. This application uses a safety servo driver, servo motor, safety encoder, safety logic controller, and operation buttons.
The biggest difference between safe inching operation and traditional inching operation is that safe inching operation monitors the safety status of the equipment at all times, ensuring the safety of the equipment during inching operation from the fundamental electrical circuit.
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