TWI Frequently asked questions
Setting force versus punch displacement can be a useful indicator of process performance and joint quality. A characteristic curve of joint formation through all its phases (see below) is used as a benchmark against which theforce-displacement curve of every rivet set is compared. A tolerance band can be applied to the benchmark curve representing the region of acceptable process variation, established by experiments and supporting quality checks.Deviations outside the tolerance band normally indicate faults, or variations in the process or materials, which may lead to unacceptable joint quality.
Simplified example force/displacement curve for self-piercing riveting Although force/displacement monitors provide a form of process control by highlighting major deviations which signal a possible need for corrective action, the correlation between monitor indications and joint properties may not beprecise. Such monitors may be stand-alone or networked as part of a broader quality control system but, in general, are only used for robotic and safety-critical applications. Further information: FAQ: What should be checked during simple visual inspection of self-piercing riveted joints?
FAQ: What should be checked when making a detailed examination of a self-piercing riveted joint?
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