Electron Beam Pulse Control for Precise Small Bore Drilling
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Solution Overview
Problem
Existing methods for producing small holes in workpieces using electron beams face challenges in achieving precise control over the geometry and surface quality of the bore, particularly in thicker materials, and require longer processing times.
Innovation Solution
The method involves varying the energy input of the electron beam by adjusting parameters such as beam geometry, current, and path, using a vaporizable substrate to expel molten metal, and employing techniques from digital drawing to guide the beam for incremental movement, ensuring precise contour and cross-sectional control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the electron beam irradiates the workpiece for a longer duration to deepen the bore, then the bore depth increases, but the processing time increases and thermal stresses accumulate
Solution Approach 1:
The electron beam operates in pulsed mode rather than continuously, with multiple pulses applied sequentially to progressively deepen the bore. Each pulse creates a bore section, and subsequent pulses extend the bore further while allowing thermal relaxation between pulses, thus achieving deep bores without proportionally increasing total processing time or thermal stress accumulation.
Solution Approach 2:
The beam current and pulse duration are varied between different pulses to optimize the drilling process. Higher currents may be used in earlier pulses to rapidly initiate bore formation, while later pulses use adjusted parameters to refine the bore geometry and remove molten material efficiently, reducing overall processing time while maintaining bore depth.
2Productivity
If the electron beam intensity is increased to melt material faster, then the drilling speed increases, but the control precision over bore geometry deteriorates
Solution Approach 1:
By using pulsed electron beam operation with multiple pulses, the process achieves high drilling speed through cumulative material removal while maintaining geometry control. Each pulse contributes to bore deepening, and the periodic nature allows for consistent geometry formation with each pulse, preventing the geometry control deterioration that would occur with a single high-intensity continuous beam.
Solution Approach 2:
The beam current is dynamically adjusted between pulses and during pulses to optimize both drilling speed and geometry control. The system adapts beam parameters based on the drilling stage and material response, enabling fast material removal when needed while maintaining precise geometry control during critical phases of bore formation.
3Productivity
If a gas jet is used to expel molten metal from the bore, then the bore production efficiency increases, but the surface quality of the bore wall may deteriorate
Solution Approach 1:
The gas jet is activated periodically during or between electron beam pulses to expel molten metal from the bore. This periodic gas assistance removes material efficiently to maintain bore production speed, while the intermittent nature of gas application prevents continuous erosion of the bore wall surface, thus preserving surface quality while maintaining high productivity.
4Manufacturing precision
If the electron beam is moved incrementally along the workpiece path, then the bore geometry precision improves, but the processing time increases
Solution Approach 1:
The electron beam is positioned at discrete locations along the bore path corresponding to each pulse, rather than moving continuously. This periodic positioning at key locations achieves precise bore geometry through cumulative pulse effects while reducing the time required compared to continuous incremental movement, as the beam remains stationary during pulse application and only repositions between pulses.
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 allows for rapid production of bores with controlled geometry, improved surface quality, and efficient removal of molten material, suitable for thicker materials, while minimizing thermal stresses and processing time.
Implementation Method 1
When an electron beam is directed at a workpiece, especially a metallic one, the electron beam introduces highly concentrated energy into the material, causing it to melt
Implementation Method 2
Some material may also vaporize, resulting in a depression with small transverse dimensions
Implementation Method 3
The effectiveness of drilling can be increased by driving the molten metal out of the material using a gas generated by the electron beam from a substrate located behind the workpiece
Data Source
Figure 1
Figure 2a~2d
Figure 3(1)a~3(1)d
AI summary
The invention relates to a method for producing in particular conical bore holes (48) in work pieces (22), wherein the contouring and cross-sectional form of the bore hole (48) can be influenced in that one or a plurality of operating parameters are changed, which parameters are selected from the following group: pulse length, beam diameter, beam current, acceleration voltage, beam focusing, deviation of the electron beam (12) from a beam axis, movement velocity of the electron beam (12) over the work piece (22).