Crane Monitoring Keeps Hotpoint Production Spinning

July 2001
A Crane Electronics TorqueStar torque monitoring/data logging device and CheckStar electronic torque transducers have provided many benefits for washing machine manufacturer Hotpoint at its Clwyd factory.

Washing machines are among the more complicated ‘white goods’, including a wide range of moving parts, pipe connections and electrical components. In operation the entire assembly heats up and cools down over a relatively short time period and the nature of its operation means that there is inevitably a lot of vibration. This combination of factors places exceptional loads on some components which can result in service failure/warranty charges if the fasteners involved are not correctly torqued down.

The company had been aware of this for some years and introduced statistical process control check on ‘preferred torques’, by which means it referred to identified critical assembly operations. The checks carried out under this regime were compiled using manually read torque meters and analysed and charted manually. The result was effective torque control provided that the regime of regular checks was maintained.

Checking was carried out by team leaders who, with necessary training, became proficient. Due to its importance within the assembly function, Hotpoint set up a working group with the aim of developing a torque control system that would prove workable and reliable under contemporary manufacturing conditions.

The TorqueStar/CheckStar combination has proven to be an effective long term solution. One of the reasons is the light weight and portability of the system allowing it to be easily carried to workstations where it was needed. The unit also allows the test data to be logged and analysed in situ, providing a minimal time lag between identification of an incorrect tool and corrective action. In use the instrument is taken down the line and checks are carried out on-line by inserting the CheckStar transducer unit between the air tool and the socket or driver used to tighten the fastener.

A series of fasteners are torqued down to provide a statistical sample and the analysis is carried out on the spot. In addition, however, the data is logged by the instrument for transfer to a PC for production of relevant charts and reports. Archived data is logged against batch codes within the factory management information system.