Laser Piercing Bulge Removal via Segmented Gas Pressure
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Solution Overview
Problem
During laser cutting of metal workpieces, bulges of molten and re-solidifying metal or metal oxide form around piercing holes, especially in thicker materials, causing adhesion issues that interfere with internal geometry cutting and small component processing, and existing methods are inefficient in preventing these bulges.
Innovation Solution
A method involving a laser beam and process gases, where a piercing hole is initially formed partially, followed by removal of the bulge using a higher-pressure gas nozzle movement, and then completed with improved gas penetration and laser focus adjustment to prevent bulge formation, allowing for precise and clean hole creation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a laser beam is used to pierce through thick metal workpieces, then the piercing operation can be completed, but bulges of molten and re-solidifying metal or metal oxide form around the piercing hole
Solution Approach 1:
The patent applies preliminary action by performing a first piercing operation that stops before completing the through-hole, allowing the workpiece surface to remain intact. This preliminary piercing creates a starting point for the final piercing without forming harmful bulges, as the laser energy is controlled to not penetrate completely through the workpiece in the initial stage.
Solution Approach 2:
The piercing operation is segmented into multiple distinct steps: a first piercing operation that creates an initial hole without completing the through-pierce, followed by a second piercing operation that completes the through-hole. This segmentation allows each step to be optimized independently, preventing bulge formation while maintaining productivity.
2Ease of manufacture
If the focal point of the laser beam is located above the workpiece surface, then a bulge of oxidized slag is formed that is relatively easy to remove, but the piercing depth is limited
Solution Approach 1:
The patent applies dynamics by changing the focal point position of the laser beam between different operation stages. In the first piercing operation, the focal point is positioned above the workpiece surface to create an oxidized slag bulge that is easy to remove. In the second piercing operation, the focal point is repositioned to achieve complete penetration. This dynamic adjustment of the focal point allows optimization for both bulge removal ease and piercing depth at different stages.
3Productivity
If the distance between nozzle and workpiece surface is reduced during full piercing, then the focal point can be deeper in the workpiece and gas injection is improved, but the bulge removal capability is reduced
Solution Approach 1:
The patent segments the piercing operation into two distinct phases with different nozzle distances. The first piercing operation uses a greater nozzle distance to create an oxidized slag bulge that is easy to remove. The second piercing operation uses a reduced nozzle distance to improve gas injection and achieve complete penetration efficiently. This segmentation allows each phase to be optimized for its specific function without compromise.
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 method effectively reduces or prevents bulge formation, enabling more accurate and efficient cutting of small features and internal geometries in thicker metal workpieces, improving the reliability of the laser cutting process.
Implementation Method 1
forming a piercing hole in the workpiece that does not go all the way through by piercing the workpiece by means of the laser beam
Implementation Method 2
In the case where oxygen is used as the process gas, due to the reaction between the molten workpiece material and the oxygen, a bulge of oxidized slag is formed
Implementation Method 3
removing a bulge deposited in step a) around the piercing hole on the workpiece surface by means of the process gas and/or an inert gas, whose gas pressure is higher than in step a)
Implementation Method 4
In step a) the focal point of the laser beam is located above the workpiece surface
Data Source
AI summary
Methods and systems are implemented for forming a through hole in a workpiece using a laser beam and a process gas, such as oxygen or nitrogen, coming from a gas nozzle. A hole is formed in the workpiece using the laser beam and a process gas emerging from a gas nozzle, such that the formed hole extends only partially through the workpiece. A bulge deposited while forming the hole partially through the workpiece is removed from the workpiece surface by directing a flow of gas through the nozzle toward the workpiece surface as the nozzle is moved with the laser beam switched off, the flow of gas being delivered to the nozzle at a higher pressure than the process gas is delivered to the nozzle during forming the hole partially through the workpiece. Then, the hole is fully pierced through the workpiece by the laser beam using the process gas.