In laser cutting, the quality of hole penetration directly determines the stability of subsequent cuts. For thick materials, incomplete penetration often results in rough cut surfaces, severe slag accumulation, and even nozzle damage. Using three-stage penetration technology as an example, this article provides an in-depth analysis of penetration principles, parameter settings, and solutions to common issues, helping you effortlessly tackle penetration challenges across various thickness materials.
Why Do Thick Plates Need Multi-Stage Piercing?
The laser cutting piercing process involves local melting of material by high-energy laser, followed by slag blowing off with auxiliary gas. The thicker the plate, the more difficult the piercing becomes, due to the following reasons:
- Accumulation of heat is slow, and energy cannot penetrate deep.
- Difficult to discharge slag and easy to block the channel.
- The oxidation reaction is intense and carbon steel is prone to blast hole.
Therefore, the traditional single-stage piercing is prone to melt metal spattering (explosion), incomplete piercing and nozzle contamination caused by air flow backflow.
The solution is multi-stage progressive piercing (e.g. three-stage piercing).
Explanation of the Principle of Third-Order Piercing
Third-stage piercing achieves sheet penetration through three distinct light-emitting phases, each employing different energy parameters. The process follows a logical sequence: initial high-energy pulses rapidly create oxygen entry points, followed by progressively lower energy levels with extended exposure duration until complete penetration. The required number of piercing stages increases proportionally with the sheet thickness.
The specific process is as follows:
Initial piercing: Position the cutting head at a higher level with zero focal length, then apply high-energy parameters (high power, high frequency, medium duty cycle) to create shallow grooves on the sheet metal. This reduces the material thickness while allowing oxygen penetration. Subsequently, cease the polishing and blowing process.
This phase aims to form shallow surface grooves that minimize subsequent piercing depth, enhance oxygen permeability, and facilitate the combustion reaction.
For the second piercing: lower the cutting head height and shift the focus to negative focal length to concentrate energy on the plate. Use reduced energy (high power, low frequency, and lower duty cycle) to emit light while extending the duration. Then stop the light and blow air. This stage aims to stabilize the expanding channel, prevent slag accumulation, and avoid excessive energy-induced piercing.
Third piercing: The cutting head continues to descend to lower the focus, maintaining the previous stage's lower energy level (high power, low frequency, reduced duty cycle) and extended exposure time, aiming to penetrate the remaining material at the bottom.