Laser Through-Hole Machining With Backside Gas Pressure Control
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Solution Overview
Problem
Existing laser machining methods face strain and crack issues when forming a large number of through-holes, particularly in annular workpieces with high aspect ratios, due to heat input and recasting during laser processing.
Innovation Solution
A laser machining method involving a higher gas pressure on the back surface of the workpiece than the front, combined with a lower repetition frequency for the pulsed laser used in the finishing step, balances heat exhaust and input, reducing heat storage and recasting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser machining is performed with high repetition frequency to reduce machining time, then productivity is improved, but heat storage increases causing strain and cracks
Solution Approach 1:
The patent applies periodic action by using pulsed laser irradiation with specific duty cycles and repetition frequencies. The laser operates in pulses rather than continuously, allowing heat to dissipate between pulses. By controlling the duty cycle (ratio of pulse on-time to total cycle time) and repetition frequency, the system achieves efficient machining while preventing excessive heat accumulation that would cause strain and cracks.
Solution Approach 2:
The patent employs parameter changes by systematically adjusting laser processing parameters including repetition frequency (5Hz to 500Hz), pulse width (10ns to 1000ns), and duty cycle (10% to 90%). These parameter variations allow optimization of the balance between machining efficiency and heat control. The gas pressure parameters (front surface: 0.01-0.1MPa, back surface: 0.03-0.3MPa) are also optimized to enhance heat removal and reduce heat storage.
2Temperature
If gas pressure on back surface is increased to reduce heat storage, then heat control is improved, but gas supply system complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the gas supply system into separate front surface and back surface gas supply paths. This allows independent control of gas pressure on each surface of the workpiece. The front surface gas supply (0.01-0.1MPa) and back surface gas supply (0.03-0.3MPa) can be optimized separately, with the back surface providing enhanced heat removal through controlled pressure without requiring complex integrated control systems.
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 suppresses strain and crack formation by minimizing heat storage within the workpiece, allowing for increased shots in the finishing step and reducing the need for post-machining corrections.
Implementation Method 1
forming through-holes in the workpiece by irradiating the workpiece with a pulsed laser having a first repetition frequency from the front surface side of the workpiece
Implementation Method 2
a gas pressure on the back surface side of the workpiece to be higher than a gas pressure on a front surface side of the workpiece
Implementation Method 3
irradiating an inner surface of the through-holes with a pulsed laser having a second repetition frequency lower than the first repetition frequency
Data Source
AI summary
Provided is a laser machining method with which strain occurring in a workpiece can be reduced even when a large number of through-holes are formed. The laser machining method includes: a gas supply step (S3) of making a gas pressure on the back surface side of a workpiece 1 higher than a gas pressure on the front surface side of the workpiece 1; a deep hole machining step (S5) of irradiating the workpiece 1 from the front surface side with a pulsed laser having a first repetition frequency f1, thereby forming through-holes A in the workpiece 1; and a hole finishing step (S7) of irradiating the inner surface of the through-holes A with a pulsed laser having a second repetition frequency f2 that is lower than the first repetition frequency f1.