Screw Joint Tightening Using Torque-Angle Curve Change Detection
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Solution Overview
Problem
Existing methods for tightening screw connections using torque or angle-controlled screwdriver units require precise specification of limit values which vary with screw geometries and materials, leading to errors and inefficiencies, as parameterizable calculation models are complex and prone to mistakes.
Innovation Solution
A method that evaluates torque and angle of rotation in real-time during tightening to determine changes in screw connection properties, using a torque-angle curve pattern to predict when the desired preload is reached, allowing for online control and precise termination of the tightening process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If parameterizable calculation models are used to determine torque and angle limit values, then the ease of operation is improved, but the reliability deteriorates due to errors in parameter inputs and model complexity
Solution Approach 1:
The system performs self-characterization by automatically determining the torque-angle curve pattern through test runs without requiring external parameter input. The screw connection itself provides the necessary information through its mechanical behavior during tightening, eliminating the need for manual parameter entry and model selection.
Solution Approach 2:
Test runs are performed before the actual tightening operation to characterize the screw connection. The torque-angle curve pattern is determined in advance through these preliminary tests, allowing the system to adapt to the specific screw connection type before production tightening begins.
2Manufacturing precision
If torque or angle limit values are specified for tightening control, then the manufacturing precision is improved, but the device complexity increases due to parameter specification requirements
Solution Approach 1:
The system automatically determines the torque-angle curve pattern and derives control parameters from it without requiring external parameter input. The screw connection characterizes itself through its mechanical behavior, eliminating the need for complex parameter specification by the user.
Solution Approach 2:
The evaluation device uses a universal approach by determining the torque-angle curve pattern that applies to all tightening phases. This single pattern serves multiple purposes: characterizing the screw connection, determining control parameters, and enabling adaptive tightening control across different screw types.
3Reliability
If test runs are performed to characterize screw connections, then the reliability is improved, but the productivity decreases due to additional time required
Solution Approach 1:
Test runs are performed once during setup to characterize each screw connection type. The determined torque-angle curve pattern is then reused for all subsequent tightening operations of the same screw type, making the initial time investment amortized over many production cycles.
Solution Approach 2:
The torque-angle curve pattern determined from test runs is copied and applied to control subsequent tightening operations. The system creates a reference model from the test data that can be reused without repeating the full characterization process for each individual screw.
Data Source
Figure 1
AI summary
The invention relates to a method and a device for tightening a screw joint with a motor-operated screwdriver unit, in which the angle of rotation and the torque are determined during the tightening, so as to be able to stop the tightening process once a desired tightening strain has been reached. According to the invention, an increase in the torque is determined by a determining device in a first tightening area by means of the angle of rotation, and a change in the increase in the torque is determined by means of the angle of rotation in a second, subsequent tightening area. When a maximum permitted change in the increase and/or rate of change, determined on the basis of the increase in the first tightening area, is reached or exceeded, the screwdriver unit is stopped by a control device.