Torque Impulse Wrench Calibration for Screw Joint Quality
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing torque impulse wrenches face challenges in accurately measuring the torque transferred to screw joints and the resulting pre-tension level due to dynamic torque transfer, making it difficult to ensure consistent and reliable tightening processes.
Innovation Solution
A method that relies on repetition checking of tightening parameter values against pre-determined reference values obtained during a calibration process, using a torque impulse wrench with a mechanical shut-off and sensors, to ensure correct pre-tension levels are maintained, eliminating the need for direct torque or pre-tension measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque values are measured by an in-line torque transducer during impulse tightening, then torque measurement is obtained, but the measurement does not give true information of the pre-tension level obtained in the screw joint
Solution Approach 1:
The patent uses an intermediary approach by introducing a reference tightening process and statistical deviation analysis as a mediator between the torque transducer measurements and the actual pre-tension level assessment. Instead of directly trusting the torque measurements, the system compares them against reference values from a calibrated tightening process, using the deviation as an indirect indicator of pre-tension accuracy.
Solution Approach 2:
The system implements feedback by continuously monitoring the deviation between measured torque values and reference torque values, then using this feedback to assess whether the pre-tension level is within acceptable ranges. The feedback loop allows the system to adjust and validate tightening quality based on statistical comparison rather than direct measurement.
2Measurement precision
If direct torque or pre-tension measurement is used to monitor tightening quality, then accurate pre-tension information is obtained, but the measurement system becomes complex and unreliable due to dynamic torque transfer
Solution Approach 1:
The patent creates a copy of the tightening process in the form of a reference tightening procedure performed during calibration. This reference copy serves as a template against which all production tightenings are compared. Instead of directly measuring pre-tension, the system copies the parameter patterns from a known good tightening and uses statistical comparison to validate subsequent tightenings.
Solution Approach 2:
The system changes the approach from direct physical measurement of pre-tension to statistical parameter analysis. By transforming the problem from measuring physical quantities (torque, pre-tension) to analyzing statistical deviations of process parameters from reference values, the system achieves reliable quality monitoring without complex measurement equipment.
3Productivity
If torque impulse wrench with shut-off function is used to control pre-tension, then tightening efficiency is improved, but accurate measurement of transferred torque and achieved pre-tension becomes difficult
Solution Approach 1:
The patent applies preliminary action by performing a calibration tightening process before production tightening. During this preliminary phase, reference parameter values are established and stored. These pre-determined reference values enable subsequent production tightenings to be validated through comparison without requiring complex real-time measurement systems.
Solution Approach 2:
The system replaces the mechanical measurement approach (direct torque transducer readings) with an electronic/information-based approach (statistical comparison of parameter values). By substituting physical measurement with data analysis, the system maintains the simplicity and speed of impulse tightening while achieving reliable quality control through computational methods.
Data Source
AI summary
A number of pre-production calibration tightenings are performed at a screw joint identical to a screw joint used in production and using the same impulse wrench as to be used in production tightening. The value of one or more tightening related parameters are registered at the attainment of the desired pre-tension level, and those parameter values are used to statistically form a basis for a reference set-up. The tightening parameter values registered during production tightening are compared to the reference set-up, and an indication is obtained as to discrepancies between the reference set-up and the actually registered parameter values to get an indication as to whether the impulse wrench is malfunctioning and/or the screw joint is faulty.