Flow-Hole Screw Process Control for Precise Thread Transition

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Solution Overview

Problem

Existing joining processes using flow-hole screws face challenges in accurately transitioning between process steps, particularly due to variations in workpiece thickness tolerances and material properties, which can lead to improper thread formation or damage.

Innovation Solution

The method involves measuring process parameters such as speed, torque, and feed force during the flow-hole and thread-forming process, smoothing these data to predict future values, and using the difference between actual and smoothed values to adjust process parameters, thereby controlling the transition between process steps.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the transition between process steps is controlled based on fixed penetration depth thresholds, then the control method is simple, but the manufacturing precision deteriorates due to workpiece thickness tolerances and material property variations

Engineering Contradiction:

Improvecontrol method simplicityVSAvoidthread formation precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent implements feedback control by continuously monitoring process parameters (torque, speed, feed force) and comparing actual values against reference curves. The system dynamically adjusts process parameters based on deviations detected through this feedback mechanism, ensuring precise thread formation despite workpiece thickness variations and material property differences.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent transitions from static fixed-threshold control to dynamic control by using continuously monitored process parameters that adapt in real-time. The control system adjusts rotation speed, feed force, and torque dynamically based on the actual process state, allowing the control method to accommodate variations in workpiece thickness and material properties while maintaining manufacturing precision.

Inventive Principle:

Principle #15Dynamics

2Productivity

If the screw penetrates through the workpiece too early due to thickness tolerance variations, then the process is faster, but the thread formation quality deteriorates due to excessive rotation speed and process force

Engineering Contradiction:

Improveprocess speedVSAvoidthread formation quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The feedback control system continuously monitors process parameters during penetration and compares them against reference curves. When the screw penetrates earlier than expected due to thickness variations, the system detects deviations in torque, speed, or feed force and dynamically adjusts parameters to prevent excessive rotation speed and force, thereby maintaining thread formation quality while preserving process speed.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent uses preliminary reference curves that define the expected process parameter progression throughout the joining process. By comparing actual parameters against these pre-established reference profiles, the system can anticipate and prevent thread formation quality issues before they occur, even when penetration timing varies due to workpiece thickness tolerances.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If process parameters are adjusted based on multiple monitored parameters with smoothing and reference curve comparison, then the manufacturing precision improves, but the device complexity increases

Engineering Contradiction:

Improveprocess control precisionVSAvoidcontrol system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces a control system as an intermediary between the physical joining process and the parameter adjustment mechanisms. This intermediary system performs smoothing operations and reference curve comparisons to translate raw sensor data into meaningful control decisions, managing the complexity of coordinating multiple parameters while maintaining manufacturing precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12343786B2Method and device for monitoring and/or control of a flow-hole and thread-forming process

Publication Date: 2025.07.01 ATLAS COPCO IAS GMBH

AI summary

A method and a device are provided for simplifying a flow-hole screw process, in which the difference between a process parameter and its smoothed value is employed as a criterion for changing said process parameter or another process parameter in order in particular to be able to determine the changeover point between hole forming and thread forming.