Nut runner controllers are matched with nut runners in precision fastening and assembly applications in which torque control is important. Both electric and pneumatic devices are available. Pneumatic nut runner controllers are designed to control air-powered nut runners, typically on assembly lines or in fixed locations. Electric nut runner controllers receive 115 VAC, 230 VAC, or 480 VAC electrical inputs and provide DC outputs to electric nutrunners. Most pneumatic and electric nut runner controllers include between 1 and 10 channels and can drive multiple nutrunners. Common features include soft starting, automatic shutoff, and remote control. Soft starting increases torque gradually in order to minimize cross-threading. Automatic shutoff is activated when a torque or angle limit is achieved. Some nut runner controllers interface to personal computers (PC) or include an integral central processing unit (CPU). Others interface to programmable logic controllers (PLCs) or use network communications.
Selecting Nut Runner Controllers
Selecting nut runner controllers requires an analysis of user interface specifications. Analog front panels include manual controls such as potentiometers, dials, and switches. Typically, readouts are displayed on needle-based meter or with light emitting diode (LED) indicators. Digital front panels allow users to setup or program nut runner controllers with digital keypads or menus. Devices that are interfaced to PCs typically feature a serial or parallel interface along with application software for control and monitoring. Common serial interfaces include RS232, RS485 and universal serial bus (USB), a 4-wire, 12-Mbps serial bus for low-to-medium speed peripheral device connections. Popular parallel interfaces include the general-purpose interface bus (GPIB), a standard developed by Hewlett Packard (HP) and called the HPIB bus. GPIB is also known as the IEEE 488 bus, which is electrically equivalent to the IEC 625 bus.
Nut runner controllers are often used as a diagnostic tool to determine characteristics such as strip-out torque, prevailing or drag torque, and fastener yield point. They are also used to check hole-size consistency and fastener quality. Data logging allows users to compare part batches and the effects of shift changes or line maintenance on production. At long distances, noise from low-voltage analog signals can degrade torque control performance. Consequently, many newer nut runner controllers use digital connections that allow nut runners to operate farther away from the control cabinet with no noticeable loss of signal.