Screw Unit Torque Trend Line Intersection for Head Contact Detection
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Solution Overview
Problem
Automated screwing processes, particularly with self-tapping screws, face challenges in reliably detecting head contact due to varying torque curves, requiring complex parameterization and specialized knowledge, which can lead to incorrect screw connections.
Innovation Solution
A screwing unit with a control unit that records torque values and generates a torque profile as a function of rotation angle, using a monitoring module to derive a trend line and set a tolerance line to identify head contact by intersecting the trend line with the tolerance line, avoiding mistaken identification of natural fluctuations as head contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex parameterization is used to detect head contact in automated screwing processes, then measurement precision is improved, but device complexity increases and ease of operation deteriorates
Solution Approach 1:
The monitoring module automatically detects head contact by evaluating the torque curve and its gradient without requiring external parameterization or user input. The system serves itself by using its own measured data (torque values and rotation angle) to determine the head contact point, eliminating the need for complex parameter setup while maintaining high detection accuracy
Solution Approach 2:
The invention changes the approach from using fixed threshold parameters to dynamically evaluating the gradient of the torque curve. By monitoring how the torque changes relative to rotation angle and detecting characteristic gradient changes, the system achieves accurate head contact detection without requiring complex parameterization for different applications
2Measurement precision
If complex parameterization is used to detect head contact, then measurement precision is improved, but ease of operation worsens due to requiring specialized knowledge
Solution Approach 1:
The monitoring module autonomously evaluates the torque curve and determines head contact without requiring operator intervention or specialized knowledge. The system automatically processes the torque data and identifies the head contact point based on characteristic gradient changes, making the process simple to operate while maintaining high precision
Solution Approach 2:
The invention replaces complex parameter-based detection methods with a gradient evaluation approach that automatically adapts to different applications. Instead of requiring operators to set parameters based on material knowledge, the system uses mathematical evaluation of torque curve characteristics to detect head contact, simplifying operation while maintaining accuracy
3Measurement precision
If gradient-based head contact detection is used, then measurement precision is improved, but reliability deteriorates due to mistaken identification of natural fluctuations
Solution Approach 1:
The monitoring module dynamically evaluates the torque curve gradient in relation to the rotation angle, adapting to the specific characteristics of each screwing process. By continuously monitoring how the gradient changes relative to the angular position and identifying characteristic patterns, the system distinguishes true head contact from natural torque fluctuations, maintaining high precision while improving reliability
Solution Approach 2:
The system uses feedback from the torque curve evaluation to determine when head contact has occurred. By monitoring the relationship between torque values and rotation angle and detecting characteristic gradient changes at the appropriate angular position, the system reliably identifies head contact while filtering out false signals from natural torque variations
Data Source
Figure 1~2
Figure 3~4
AI summary
The screw unit (6) serves for the reliable screwing of, in particular, self-tapping screws (2) into a workpiece (4). A torque curve (M) is monitored to reliably detect when the screw head is seated (K). A trend line (L) and a tolerance line (T) are defined for the torque curve (M) during screwing until the screw head is seated (K). The system detects when the screw head (K) is reached if the trend line or the detected torque curve (M) intersects the tolerance line (T) at a point (P). This method of determining the screw head (K) enables universal determination, independent of the specific screw pairing and the material of the workpiece (4), and especially without complex parameterization.