Flow-Hole Screw Process Control for Precise Thread Formation

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Solution Overview

Problem

The existing joining processes, particularly with flow-hole screws, face challenges in precisely controlling the transition between process steps due to tolerances in workpiece thickness and material variations, leading to potential thread destruction from premature penetration and incorrect speed changes.

Innovation Solution

The method involves using smoothed process parameters to monitor the difference between actual and predicted values of parameters like speed, torque, and penetration depth, allowing for dynamic adjustment of process conditions to ensure precise control of the joining process, independent of screw geometry and material variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If penetration depth is used as a switching criterion, then the transition between process steps can be controlled, but tolerances in workpiece thickness are not taken into account leading to premature penetration and thread damage

Engineering Contradiction:

Improvethread formation precisionVSAvoidprocess control reliability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent implements feedback control by continuously monitoring process parameters (torque, speed, penetration depth) and comparing actual values with reference values. The control system adjusts process parameters in real-time based on deviations detected during the joining process, ensuring accurate transition between flow-hole forming and thread forming stages while compensating for workpiece thickness variations.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent dynamically changes process parameters (rotational speed, feed rate, torque) based on the detected process stage and deviations from reference values. By adjusting these parameters in response to real-time feedback, the system maintains optimal conditions for each process stage and prevents premature penetration that would damage threads.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If rotational speed is increased for material flow, then the joining process progresses efficiently, but excessive rotational speed compromises proper thread formation

Engineering Contradiction:

Improvejoining process speedVSAvoidthread pitch accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent employs periodic action by systematically varying rotational speed through distinct phases: high speed during flow-hole forming to achieve material flow and penetration, then reducing to lower speed during thread forming to ensure proper thread pitch. This periodic speed variation optimizes both productivity and thread formation quality at different process stages.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies dynamics by making rotational speed a dynamic parameter that changes continuously based on process stage and real-time feedback. The system transitions from high rotational speed (for efficient material flow) to low rotational speed (for accurate thread formation) based on detected penetration depth and torque characteristics, ensuring optimal performance throughout the joining process.

Inventive Principle:

Principle #15Dynamics

3Device complexity

If process parameters are adjusted based on fixed thresholds, then the control system is simple, but it cannot adapt to material variations and geometry differences

Engineering Contradiction:

Improvecontrol system complexityVSAvoidadaptability to material and geometry variations

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent implements self-service by enabling the control system to automatically adapt to different materials and geometries through reference value storage and comparison. The system stores reference values for various workpiece types and automatically selects and adjusts parameters based on the detected workpiece characteristics, eliminating the need for manual reconfiguration and providing versatile adaptation without proportionally increasing complexity.

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables precise and adaptive control of the joining process, reducing the risk of thread destruction and ensuring clean thread formation by dynamically adjusting process parameters based on real-time data, thus optimizing the joining process across various materials and geometries.

Implementation Method 1

the screw is pressed against the workpiece with high pressure, causing the workpiece material to heat up and begin to flow

Methodology Applied

Scientific EffectFriction heating: Friction

Data Source

PatentEP4102316B1Method and device for monitoring and / or regulating a flow hole and thread-forming process

Publication Date: 2023.12.06 ATLAS COPCO IAS GMBH

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AI summary

The invention relates to a method and a device for simplifying a flow-hole screwing process, in which the difference between a process parameter and its smoothed value is used as a criterion for changing the same or another process parameter, in order to determine in particular the switching point between pull-through forming and thread forming.