# Safety The SSG-48 gripper is a force-controlled gripper for collaborative and research robots, not a certified safety component. Whoever puts it on a machine is responsible for the risk assessment of the gripper, the robot and everything around them. Read this chapter before you power the gripper; the rules here are the ones that injure a hand or destroy the gripper when they are ignored. ## Mechanical !!! danger "The jaws" The jaws are a pinch point. At a high current limit they close with up to 80 N, enough to crush a finger, and at full speed they travel the whole stroke in a fraction of a second. Never put a finger between the jaws of a powered gripper. Keep hands away during calibration, which moves the jaws over the whole stroke without any command from you. !!! warning "Start low" Test every new setup with a low current and speed: current 300 mA, speed 30. Raise them step by step once the application behaves; [Force and speed](https://docs.source-robotics.com/SSG48-gripper-docs/2/03-technical-data/force-and-speed/) says what each value means. !!! warning "Objects" A gripped object that slips, or that the jaws crush, can fly or fall. The grip force is a current limit, not a measurement: a hard object takes the full force, a soft one deforms until the force is reached. !!! warning "Hair, clothing and jewellery" The jaws catch more than fingers: long hair, loose sleeves, gloves, lanyards, rings and bracelets. Tie back long hair and take off what can be caught before you work at a powered gripper, and keep it out of the jaws' reach while they move. Wear safety glasses where a part can slip out of the grip and fly. ## Electrical !!! danger "The cable" The gripper's M8 connector carries 24 V next to the CAN bus. A cable with the wrong pinout, including the cable of the other Source Robotics robot, puts 24 V on the CAN pins and destroys the driver. Use the cable made for your robot or check every pin of your own; see [The cable](https://docs.source-robotics.com/SSG48-gripper-docs/2/04-installation/cable/). !!! warning "Supply" 24 V DC. The driver inside tolerates 12 to 29 V, but the gripper's force and speed figures assume 24 V. !!! warning "Do not unplug a powered gripper" Connect and disconnect the cable with the supply off. Hot-plugging the connector can damage the driver. !!! warning "Static" Static electricity damages the Spectral Micro driver inside the body. Unplug the supply and touch earthed metal before you open the body, set the termination switch or handle the driver, and hold the board by its edges. ## Temperature The motor has a thermistor in its windings. At 75 °C the driver raises a temperature error and the gripper goes idle; it clears when the motor has cooled and the error is cleared. A gripper holding an object at a high current for long heats up: a hold at 300 mA ran for 24 hours at 62 °C, a hold at 1600 mA tripped the limit in four minutes ([Performance tests](https://docs.source-robotics.com/SSG48-gripper-docs/2/appendix/performance/)). For a long hold, use the lowest current that holds the object. A self-built gripper without a thermistor in the windings has no protection and can burn out its motor; see [Driver configuration](https://docs.source-robotics.com/SSG48-gripper-docs/2/build/first-run/). ## Stopping the gripper - The E-stop bit of the move command (`Send_gripper_data_pack`) stops the gripper and raises the gripper E-stop error. The error stays as long as the last command carries the bit: send a command with the bit at 0, then clear it ([Errors and recovery](https://docs.source-robotics.com/SSG48-gripper-docs/2/06-operation/errors/)). - `Send_ESTOP` to the driver, or `#Idle` over UART, stops it as well. - The CAN watchdog ([Send_Watchdog](https://docs.source-robotics.com/SSG48-gripper-docs/2/reference/can/system/)) stops the gripper by itself when the host stops talking, which is the right protection for a program that may crash mid-grip. - Cutting the supply releases the grip: a motor without current holds nothing beyond the mechanism's friction, so an object can drop. None of these is a certified safety function. A machine that can hurt someone needs an emergency stop that cuts the power, independent of the gripper and the robot software. ## Care The gripper is not waterproof or dustproof: the rail and the racks are open to dust, chips and liquids. Keep it out of wet or dusty places. What to check, and when to grease the mechanism, is in [Maintenance](https://docs.source-robotics.com/SSG48-gripper-docs/2/07-maintenance/). ## Liability The SSG-48 gripper is sold as a component for people who build their own machines, and its designs are published for people who build the gripper itself. The hardware designs, the firmware and this documentation are under development and may contain errors. Whoever builds or operates a machine with the gripper is responsible for its safe design, assembly and operation. The [full disclaimer](https://github.com/Source-Robotics/SSG-48-adaptive-electric-gripper/blob/main/SAFETY_WARNING_AND_DISCLAIMER.md) is in the product repository.