Cutting drilling technology.
As a general rule, drilling a small hole in the sheet metal is necessary for any hot cutting process, with only a few exceptions where the cut may begin at the edge of the sheet metal.
In the past, a hole was punched using a punch die on a laser stamping machine before the laser cutting process began.
There are two fundamental methods for laser cutting without using a stamping device:
Sandblasting drilling
During continuous laser irradiation, the material forms a hole in the center, which is quickly removed by the flow of oxygen accompanying the laser beam, resulting in the formation of a hole.
The size of a typical hole is determined by the thickness of the plate.
The average diameter of the blast hole is approximately half the thickness of the plate, which means that the holes in thicker plates are larger and not circular.
This method should not be used on parts that require high machining precision, and is only suitable for scrap.
Furthermore, the oxygen pressure used during the drilling process is the same as that used in cutting, which results in excessive spatter.
Wrist piercing
A pulsed laser with peak power is used to melt or vaporize a small amount of material. Ordinary air or nitrogen is employed as an auxiliary gas to reduce hole expansion due to exothermic oxidation. The gas pressure is lower than that used in oxygen cutting. Each laser pulse produces small particles that are expelled and gradually penetrate. As a result, drilling through a thick plate can take several seconds.
Once drilling is complete, the auxiliary gas is immediately replaced by oxygen for cutting. This results in a smaller drilling diameter and higher quality drilling compared to shot blasting. To achieve this, the laser must not only have a higher output power, but also precise temporal and spatial characteristics of the beam. The general flow CO2 laser does not meet these requirements.
Additionally, pulse drilling requires a reliable gas control system to regulate gas type, pressure, and drilling time. To obtain high-quality cuts during pulsed drilling, the transition from pulsed drilling to continuous cutting must be taken seriously.
In theory, cutting conditions such as focal length, nozzle position and gas pressure during the acceleration period can be changed. However, in industrial production it is more practical to change the average laser power. This can be achieved by changing the pulse width, frequency, or both. Research has shown that the latter approach produces the best results.
Analysis of deformation when cutting small holes (small diameters and thicknesses).
The reason for this is because when machining a hole, the high-power laser cutter does not use the shot blast drilling method, but instead employs pulse drilling (soft punching). This causes the laser energy to be very concentrated in a small area, causing the unprocessed area to carbonize and resulting in deformation of the hole and degradation of processing quality.
In this case, it is necessary to switch from pulse drilling (soft punch) to shot blast drilling (common punch) in the processing procedure to solve the problem.
On the other hand, for less powerful laser cutting machines, it is advisable to use pulsed drilling to obtain a better surface finish for small hole cutting.
The piece has a burr when cutting low carbon steel, how to solve it.
According to the working and design principles of CO2 laser cutting, the following are analyzed as the main reasons for the formation of burrs on the workpiece:
- Incorrect laser focus position: A focus position test is required to adjust offset based on focus.
- Insufficient laser output power: It is necessary to check whether the laser generator is working properly. If so, check that the laser control knob output value is set correctly and adjust accordingly.
- Slow cutting speed: The cutting line needs to be accelerated through the operation control.
- Low purity of cutting gas: It is necessary to provide high quality cutting gas.
- Laser Focus Migration: A focus location test is required to adjust the offset based on the focus.
- Instability caused by prolonged operation of the laser cutter: The laser cutter needs to be turned off and restarted.
Burr analysis on the part when cutting stainless steel and aluminum-zinc sheets with a laser cutter.
In the case of the above situation, when cutting low-carbon steel, the factors that may cause burrs must first be considered.
However, simply increasing the cutting speed may not necessarily solve the problem, as increasing the speed does not always allow the sheet to be perforated. This is especially important when processing aluminum-zinc plates.
In this scenario, other factors of the laser cutting machine must also be taken into consideration, such as the need to replace the nozzle and check the stability of the guide movement.
Analysis of the incomplete cutting state of the laser.
After analysis, the main causes of unstable processing are identified:
Incorrect selection of the laser nozzle for plate thickness;
The cutting speed is too high and needs to be decreased.
It is also essential to note that when cutting a 5mm carbon steel plate with a laser cutting machine, it is necessary to replace the 7.5″ focal length laser lens.
The solution to abnormal sparks appears in cutting low carbon steel.
This situation can impact the quality of the cut sections of the parts. If other parameters are normal, consider the following potential causes:
- Loss of the laser nozzle, which must be replaced immediately.
- If a new nozzle is not replaced, the cutting gas pressure must be increased.
- The screw thread connecting the nozzle and laser cutting head may be loose. If this is the case, you should stop cutting immediately, inspect the laser head connection, and tighten the screw thread.
Selection of puncture points during laser cutting.
The working principle of laser beam cutting:
During the cutting process, the material is subjected to continuous laser radiation, which results in a depression in the center. The working airflow with the laser beam quickly removes the melted material, creating a hole. This hole resembles a threaded hole in thread cutting.
The laser beam uses this hole as the starting point for contour cutting. Normally, the direction of the laser beam on the flight path is perpendicular to the tangent direction of the cutting contour of the processed part.
As a result, from the moment the laser beam penetrates the steel sheet to the moment the contour is cut, there is a large change in the cutting speed in the vector direction. Specifically, the vector rotates 90°, causing the tangential direction perpendicular to the cutting profile to overlap the cutting contour. In other words, the angle with the contour tangent becomes 0°.
This rapid change in the direction of vector movement of the laser beam results in a rough cutting surface on the cut section of the processed material.
In general, when there is no roughness requirement for surface cutting in the project, manual control will not be set in the laser cutting programming, and the control software will automatically generate punch points. However, when the project requires a high roughness for the cutting section, it is important to take this issue into consideration.
Manual adjustment of the initial position of the laser beam, i.e. manual control of the puncture point, is normally necessary. This involves moving the punch point generated by the laser program to a reasonable position that meets the surface accuracy requirements of the machined parts.
