Electrode Orbital Machining for Consistent Internal Threads
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Solution Overview
Problem
Existing methods for machining internal threads in hostile environments, such as nuclear reactors, face issues like electrode wear, inconsistent thread profiles, high machining times, and the need for multiple electrode systems due to the requirement of adapting to each pitch value, which complicates remote-controlled tapping operations, especially in blind and shallow bores.
Innovation Solution
A method and apparatus for remote-controlled automatic machining that uses an electrode with pre-determined thread shape and dimensions, performing orbital movements without axis rotation, and adjusting machining parameters through multiple passes with pulsating radial movements, utilizing a single electrode that accounts for wear and maintains consistent thread profiles by modifying current pulses, pass depth, and electrode position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If electroerosion machining is used with a lead screw to drive helical movement, then the machining can be performed under remote control, but the thread profile becomes inconsistent and conical due to electrode wear
Solution Approach 1:
The electrode is subjected to vibrational movement perpendicular to its axis during machining. This vibration prevents the electrode from remaining in continuous contact with the workpiece, significantly reducing wear and maintaining consistent thread profile geometry throughout the tapping process while enabling remote control operation.
Solution Approach 2:
The machining process uses periodic pulsing of the electrode with controlled engagement and disengagement cycles. The electrode advances periodically, machines for a set duration, then retracts slightly to prevent excessive wear, repeating this cycle to maintain profile consistency over the entire tap depth.
2Productivity
If a roughing rate is used to save machining time, then productivity increases, but surface quality deteriorates with microcracking
Solution Approach 1:
The tapping process is divided into multiple sequential passes rather than attempting to complete the entire tap in a single operation. Each pass removes a portion of the material, allowing heat dissipation and reducing cumulative wear, while the final pass produces the required surface quality without microcracking.
Solution Approach 2:
The process employs periodic interruption of the machining action with retraction cycles between passes. This allows the electrode to cool, wear to be reset or compensated, and the workpiece surface to stabilize, enabling high productivity while maintaining surface quality through controlled intermittent operation.
3Manufacturing precision
If a finishing rate is used to achieve good surface quality, then manufacturing precision improves, but machining time becomes prohibitive and wear increases
Solution Approach 1:
The finishing operation is segmented into multiple light passes rather than one prolonged heavy pass. Each pass removes minimal material with the vibrational assistance, achieving the required surface quality quickly without excessive wear or time consumption.
Solution Approach 2:
Vibrational movement is maintained throughout finishing passes, allowing higher feed rates to be used without sacrificing surface quality. The vibration prevents material buildup and ensures clean cutting action, reducing total finishing time while maintaining precision.
4Device complexity
If a single electrode is used for multiple passes, then device complexity is reduced, but electrode wear increases affecting thread geometry
Solution Approach 1:
The single electrode is equipped with vibrational movement capability that actively reduces wear during each pass. This allows the same electrode to be reused for multiple passes while maintaining consistent thread profile geometry, eliminating the need for multiple specialized electrodes.
Solution Approach 2:
The electrode operates in periodic cycles with controlled engagement and retraction. During retraction phases, wear is minimized or reset, allowing the same electrode to perform multiple passes with consistent geometry. The periodic action prevents cumulative wear from degrading the thread profile.
5Speed
If the electrode rotates about its own axis during machining, then helical movement is achieved, but the method requires adapted drive systems for each pitch value
Solution Approach 1:
Instead of rotating the electrode about its own axis to achieve helical movement, the invention inverts the approach by moving the electrode in a circular path around the bore axis while keeping the electrode itself stationary or minimally rotating. This eliminates the need for complex pitch-specific drive systems.
Solution Approach 2:
A separate orbital movement mechanism acts as an intermediary between the linear feed system and the helical thread formation. This intermediary circular motion, combined with linear advancement, generates the helical path without requiring the electrode to rotate, simplifying the drive system for different pitches.
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 ensures consistent thread profiles across the entire length, reduces machining time, minimizes microcracking, and allows for efficient tapping in hostile environments with a single electrode system, adaptable to various thread standards and pitches, while maintaining a controlled and precise remote operation.
Implementation Method 1
machining the threads of the tapping by electroerosion while displacing the electrode in orbital manner inside the bore
Data Source
AI summary
The invention relates to a method for producing a thread in a bore (2) by remote automatic machining characterized in that the method consists in introducing into the bore (2) an electrode (11) provided with a thread (20) whose shape and dimensions are pre-determined according to the shape and dimensions of an inside thread to be produced, in machining the internal threads by electroerosion displacing the electrode (11) in an orbital manner in the bore (2) according to a predetermined number of operations and in adjusting the machining parameters according to each operation. A device for carrying out said method is also disclosed.