As mentioned in part one of this series, many manufacturers treat fasteners as an afterthought, but having a clearly defined fastener strategy can offer many benefits in the long term.
Another key point to consider when building a fastener strategy is joint criticality.
Looking at each joint and asking yourself, “What happens if this joint comes loose or fails completely?” is a good way to help guide your strategy. Your levels of response may look something like this:
- Level 1 – Product may cease to function, but can be easily repaired by consumer – generally not a warranty claim
- Level 2 – Product may fail but warranty claim is unlikely
- Level 3 – Product may fail and warranty claim is likely
- Level 4 – Product may fail and injure consumer
Levels 3 and 4 should help guide your strategy in friction control, locking features, and method of assembly. These joints should use controlled tightening methods and tools along with finishes having specific friction ranges engineered into them. If you are unable to incorporate the five times the diameter clamping range into the joint, locking features may also need to be incorporated to help keep things from loosening.
Warranty issues may be worth investigating when building a fastener strategy as well. If loosening or corrosion problems are prevalent, changes to the strategy may help address these claims in the future.