Internal Thread Forming with Controlled Deceleration Feed
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Solution Overview
Problem
The existing method for forming internal threads using percussion tapping tools experiences excessive cutting stress, leading to tool breakage due to axial forces during the deceleration phase, which reduces the tool's lifespan.
Innovation Solution
A method involving a combined drilling and thread forming tool that decelerates with a controlled axial feed synchronized with the rotational angle, producing a peripheral groove to reduce stress on the tool, and includes a reversing phase to guide the thread generating region out of the workpiece without material removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tool decelerates during the working phase to reach a reversal point, then the tool can reverse direction for thread formation, but excessive axial forces during deceleration cause cutting stress and tool breakage
Solution Approach 1:
The method applies preliminary action by decelerating the tool before reaching the reversal point and reducing axial feed accordingly. This preparatory deceleration prevents excessive cutting stress during the reversal phase, thereby extending tool lifespan while maintaining reliable thread formation.
Solution Approach 2:
The invention implements dynamics by continuously adjusting the axial feed rate based on the tool's rotational speed and position. During deceleration, the axial feed is reduced in proportion to the decreasing rotational speed, creating a dynamic control system that adapts to changing operational conditions and minimizes stress on the tool.
2Reliability
If the axial feed is reduced during deceleration to minimize stress, then tool lifespan is extended, but thread formation precision may be compromised
Solution Approach 1:
The method employs feedback control by continuously monitoring the tool's rotational angle and axial position, then adjusting the axial feed rate accordingly. The control system uses the stored definite relationship between axial feed and rotational angle to maintain precise thread formation while adapting feed rates to minimize stress, ensuring both tool lifespan and manufacturing precision.
Solution Approach 2:
The invention applies parameter changes by modifying the axial feed rate as a function of rotational angle during deceleration. By implementing a previously stored definite relationship (function or sequence of functions) between axial feed and rotational angle, the system dynamically adjusts parameters to balance stress reduction with thread formation accuracy.
3Productivity
If the tool continues at constant speed to the reversal point, then thread formation is efficient, but the tool experiences excessive stress and breaks
Solution Approach 1:
The method applies preliminary action by initiating deceleration before the tool reaches the reversal point. This early deceleration prevents the buildup of excessive axial forces that would otherwise cause tool breakage, while the controlled nature of the deceleration maintains acceptable thread formation efficiency.
Solution Approach 2:
The invention implements beforehand cushioning by reducing the axial feed rate in proportion to the decreasing rotational speed during deceleration. This creates a cushioning effect that absorbs the shock of reversal, protecting the tool from excessive stress while maintaining productive thread formation.
Data Source
AI summary
A method for forming a thread with a predefined thread pitch and with a predefined thread profile in a workpiece, in which a tool is used, wherein, during working movement, a thread generating region forms a thread, wherein the tool is moved during a second working phase further into the workpiece in the same forwards direction as in the working movement, as far as a reversal point, wherein the decelerating movement comprises a rotational movement in the same rotational direction as in the working movement, wherein during the decelerating movement, the axial feed movement is controlled in dependence on the rotational angle of the rotational movement of the tool and wherein the axial feed of the tool during a complete revolution, is smaller in terms of amount than the thread pitchat least during part of the decelerating movement and is zero at the reversal point.