Torquestars And Checkstars Check Truck Brake Assemblies

1997
The integrity of vehicle braking systems is crucial, and manufacturers need to be sure that the correct assembly procedure has been followed, down to the last nut and bolt. That includes being certain that the correct torque has been applied!

Lucas Heavy Duty Braking Systems, based at Cwmbran in Gwent, use four DC electric wrenches to assemble disc brake units for use on trucks. As part of the strict quality control procedure the torque applied by the guns is checked weekly. This is done using a TorqueStar intelligent readout device and three CheckStar rotary transducers from Crane Electronics.

Gareth White is the Senior Engineer who is responsible for the QC aspects of the assemblies and he specified the Crane equipment: "We used to use a small hand-held device from another supplier, but this had many drawbacks. Looking around for something better we found the Crane system and it does everything we could ever want. It is absolutely foolproof to use, and it is the only instrument we could find that gives a direct readout of process capability".

As well as the weekly patrols, the TorqueStars and CheckStars are also used periodically to measure the process capability for each gun. Fifty bolts are tightened and the TorqueStar gives a direct value for Cp and Cpk. The equipment is also used following regular gun maintenance and for troubleshooting if there is a problem on the production line. It has also been very useful in developing new products and tools, to check that the actual torques applied to fasteners are as the designers expected.

One of the advantages of the TorqueStar is the way that 'rounds' can be programmed. When this has been done, the screen on the unit tells the operator which gun is to be checked next, and which CheckStar transducer is to be used. The operator attempts to use the wrong transducer, the TorqueStar displays a warning. Gareth White was trained to program and use the TorqueStar: "A Crane engineer came down and spent an hour with each of us that was going to use it. Programming is certainly easy, and then to use it is just a case of 'plug in and go', it couldn't be more simple.”�

The transducer fits between the gun and the fastener being tightened, so a true measure of the torque being applied is given. The reading is displayed and also stored so it can be downloaded and analysed on the computer later on".

Using the TorqueStar and CheckStars has provided more control over the production quality. The functionality, ease of use, and robust build, mean that it has very quickly been accepted as part of the quality control armoury.