Many joints consist of more than one fastener and bringing together surfaces that are not completely flat can be a very challenging torque problem. The sequence of tightening fasteners can have a major influence on the resulting preload and clamping force, which is what holds two parts together. With such joints, consideration should be given to specifying the sequence in which the fasteners are to be tightened. Because the joint surfaces compress, tightening one fastener in the vicinity of another will affect the preload generated by the first fastener tightened. This is called Cross Talk.

A good tightening sequence ensures that an even preload distribution is achieved in the joint. Since joints containing conventional gaskets have a comparatively low compressive stiffness, bolt preloads in such joints are particularly sensitive to the tightening sequence. Based on experience, if the bolts are in a circular pattern, a cris-cross (star) tightening pattern would normally be specified. For non-circular bolt patterns, a spiral pattern starting at the middle would normally be specified. On critical joints or joints that exhibit relaxation, a tightening pattern that tightens the fasteners more than once can be specified to ensure an even preload distribution.

Sequence based fastening is critical to proper process control and a quality fastening result for many applications. If an assembly exhibits cross talk, a phenomenon where torque to one fastener changes the result to another in the in fastening pattern, altering the sequence is often necessary to achieve proper results. Position Control torque arms are designed to reduce the risk of improperly fastened screws, ensuring that every screw is in the correctly tightened in the correct sequence. An encoded torque arm is perfect because it guides the operators sequence and provides feedback if done incorrectly.

Read the rest of this page »

Position Control torque arms are designed to reduce the risk of improperly fastened screws, ensuring that every screw is in the correctly tightened in the correct sequence. Using a Position Control torque arm is like putting the eyes and ears of a quality control manager where they are needed most – right on the assembly area.

“Sequence based fastening is critical to proper process control and a quality fastening result for many applications,” said Brad Mountz, President & CEO of Mountz, Inc. “If an assembly exhibits cross talk, a phenomenon where torque to one fastener changes the result to another in the in fastening pattern, altering the sequence is often necessary to achieve proper results. An encoded torque arm is perfect because it guides the operators sequence and provides feedback if done incorrectly.”

The new EZ-Glider Position Control torque arms by Mountz Inc. help manufacturers detect and eliminate costly screw-fastening errors during the assembly process. Assembly sequences are easily programmed for the torque arm from an easy-to-use control box. Up to nine sequence programs can be stored and are manually or automatically selected for easy recall.

Read the rest of this page »