Technical difficulties are often the most frustrating thing we face during automation technology. When it doesn’t work, sometimes it makes us angry. We’ll say, relax and sit. Do some research on that particular project and learn. DO NOT learn and operate at the same time. First, finish learning and then try them out. Indeed, you will find a suitable solution, or else you will find a way to learn more about solving the problem. However, laser cutting technology is a combination of multiple functions, which means technical obstacles might appear due to lack of maintenance or functional inability. Today’s content will demonstrate eleven common technical difficulties we face during sheet metal laser cutting.
The Most Common 11 Technical Difficulties of Sheet Metal Laser Cutting
Operators often encounter various issues when cutting sheet metal with a laser cutting device. Depending on the seriousness and effect of the problems, we have made a list of the eleven most common technical difficulties that are more habitual in laser sheet metal cutting. We will describe the issues, the science behind the problem, and the solution. To ensure better quality cutting, we must be familiar with these technical difficulties.
The majority of beginners experience numerous technical difficulties when using a laser cutting system to cut various materials. The most common issues they may experience are ineffective cutting due to material thickness or dross-clinging material that raises the component’s temperature. As a result, the proposed plate would be a complete waste of material. To address these two issues, we must first understand the fundamentals of laser cutting material forms, consistency, and composition.
Material types and quality
Every laser cutting machine has maximum thickness cutting limitations. But what if the specification defines a steel thickness limit of up to 1 inch, but you still face trouble cutting 0.5 inches of thick carbon steel? In this case, the laser cutting thickness limitations depend on the heat conductivity through the material, surface reflection at 10.6 microns, alloy forms, alloy vaporization points, molten material surface tension, and component geometry.
- The thermal runaway increases with the increase of the material thickness considering all these properties.
- The laser becomes sharper by highly reducing the spot size and focusing the beam.
- Highly focussing the assist gas improves the laser’s ability. Assist gas helps in combustion and blow the molten metal.
- Those metals with higher conductivity provide inefficient cutting, such as aluminium. In this situation, efficient energy transformation will make an efficient cut.
- Part Geometry affects more than other physical states of the thermal process. The corner or smaller areas absorb more energy that increases the blowout. In short, the more complex material geometry, it is harder to compromise cutting speed.
- The consistency of the material has a significant influence on laser cutting. Ensure that the sheet metal is clean, pickled, and free of oil. Low-grade metals are highly reactive to the thermal process in this case, especially during the oxygen processing period.
The material composition has a more significant effect on laser processing than on any other physical state of a material. In this case, laser processing typically impacts the conductivity and viscosity of metal in liquid form. The liquid metal’s surface tension influences the degree of dross particles at the part’s exit edge. The waste materials will fly away if the viscosity layer is thin in this situation. The dross particle will stick to the material and increase its temperature if the coating is thick.
Carbon steels are high-quality sheet metal that ignites fast when exposed to a laser beam. This type of material, in comparison to homogeneous materials, would have several melting points. Carbon steel producers in various locations, on the other hand, can not use the same structural components in their operations. Owing to different melting points, you can have difficulty cutting the material in this situation. Consider the surface condition, which involves scale, coatings, filth, and surface impurities, when selecting a high-quality carbon steel material.
Setup Time Issue
Laser cutting can take a long time when cutting unfamiliar materials because of the setup time. This process is influenced by nozzle size, rated power, focal length adjustment, assist gas and pressure, and speed. On the other hand, these parameters are so critical that the laser won’t cut the material if you don’t get them right.
HAZ or heat-affected zone is a common term used in laser cutting technology. HAZ forms when the temperature on the projected place rises above the critical transformation point results distortion. Distortion may happen in multiple ways.
- When a laser projects on thin materials with a thickness of 0.001 to 0.005 inches, it causes this effect. Since a recast layer forms on the outside, more fragile materials are more vulnerable to distortion.
- The sudden ruse in the temperature of the materials near the cutting zone creates distortion.
- Rapid solidification of the cutting zone may also trigger it.
In this situation, using a water quenching device during the laser cutting process will help to reduce the heat produced.
Sheet metal perforation issue
Perforation is a standard method of industrial packaging and storage, especially for food. Perforation of sheet metal is also common for ventilation and other air facilities. However, there are a few technical problems with hole size and form during this sheet metal perforation. To solve these challenges, you must grasp the intricacies of sheet metal perforation. There are two methods for the laser cutting machine for sheet metal perforation.
This perforation technology let high power peak to melt or vaporize a small amount of material. In this situation, air or nitrogen gas is expected as the auxiliary gas for hole expansion. At the time of cutting, the gas pressure is lower than the oxygen pressure. Each incident laser creates a tiny hole in the material. After the perforation, the auxiliary gas replaces with the oxygen gas for cutting. In the past, the gap was punched out and cut immediately using a punching mould in the laser stamping unit. At present, using these pulse and blasting perforation methods, we can create the spot, and after that, the laser can perform the cutting.
- The diameter of the perforated hole is smaller. The perforation standard here is superior to that of blasting perforation.
- In this process, the laser has high power, time, and space characteristics of the beam.
- The transition technology from this perforation process to continuous cutting has to be accurate to obtain a high-quality incision.
The material creates a pit after continuous laser irradiation, and the oxygen flow with the laser beam destroys the fused material to make a small hole. This size depends on the thickness of the plate. The average diameter of the blasting perforation is half of the plate thickness. In this case, for the thicker plate, the blasting perforation is more extensive and not round.
If you are looking for high machining accuracy, DO NOT go for blasting perforation. It is only suitable for scrap.
Cutting/engraving depth is insufficient
This problem is one of the most commonly seen technological issues by the operators. Insufficient cutting/engraving depth occurs due to the following reasons.
- The focal point may not be in the correct position. If you find this issue, adjust it according to the provided laser company’s methods.
- The laser tube is failing to start, and if increasing the power doesn’t work, then replacing the laser tube will the best choice.
- The laser output power or power supply is too low. If adjusting it doesn’t work, replacing it would be the best way to fix the problem.
- Sometimes, due to the cutting speed, the insufficient cutting may occur. So, slowing down the rate of the cutting or engraving speed may solve this issue.
During the laser cutting process, you might have observed that the laser sliced the sheet metal parts. If so, the following situation is the primary condition for creating this unstable processing.
- The selected laser nozzle didn’t suit the thickness of the sheet metal. In this case, know the suitable laser nozzle for the appropriate thickness of the material. If it didn’t work, we suggest asking your laser company to change the nozzle. Let’s say you got a 5mm carbon steel plate for laser cutting. To cut such sheet metal, you need to get a 7.5″ focal length of the laser lens.
- The incomplete cut may also happen due to the linear motion of the laser gun. In this case, adjust the linear speed of the laser gun.
While operating the laser cutting machine, you may encounter a buzzing sound from the sheet metal while the laser was hitting. The following factors are the cause of the burr sound issue on the sheet metal.
- Focal length can be an issue in this matter. If you have already fixed the focal length problem, then the following factors might be the reason.
- If the cutting speed is too slow, it may cause a burring sound. Increasing it will solve the problem.
- A long time using the laser cutter can cause instability. In this case, restarting the device will solve this issue.
- If the laser source’s output power is not sufficient, this will cause burring sound on the sheet metal. Adjusting it will solve the problem right away.
Sparks affect the quality of the laser cutting edges of the sheet metal. If the above factors are good, then the following situations could be the reason behind this issue.
- Due to the long-time of using the laser, the nozzle may lose its former ability. In this situation, replacing the nozzle would be the right choice to solve this issue.
- Gas pressure might be an issue in this situation. Increasing the gas pressure might solve this problem as well.
- The screw thread at the joint of the laser nozzle and the laser gun is loosely fitted. The operator should not continue cutting at this situation and shut down the device immediately. Check out the screws and reinstall them.
Small hole deformation
This issue occurs from the malfunctioned laser pulse perforation process. A single leaser beam forms a small hole on the plate in the laser pulse perforation phase. However, owing to mechanical errors, a high-power laser concentrated in a small region causes a deformed spot.
In this situation, changing to blasting perforation method from pulse perforation in the program section can solve this issue. On the other hand, for lower power laser cutting machines, adopting hole processing to obtain a good surface finishing can be a good choice.
Difficult to primary combustion process under quasi-equilibrium state
You can run into this issue if the sheet metal is thicker than 10mm. Moreover, this question resembles the unsteady combustion of an iron cutting edge. According to the quasi-equilibrium process, the ignition point on the top of the slip must be continuous. First, the energy released from the iron oxide doesn’t ensure the constant combustion process. Second, the oxygen flow reduces the cutting edge temperature. Third, the iron oxide layer formed after the combustion covers the workpieces’ surface and diffuses oxygen.
- The diameter of the oxygen flow act on the surface is larger than the laser beam diameter.
- The cutting speed will generally be slow cutting thick plate.
- After a while, due to a decrease in oxygen concentration, the device extinguishes the combustion process.
Oxygen purity and pressure problem
This technical issue is also for the sheet metal of 10 mm+ thick plates. You may encounter some general technical problems due to the impurity in the oxygen. The purity of the oxygen flow has a significant role in the cutting process. In this case, when the oxygen purity decreases by 0.9%, the combustion rate decreases by 10% and for 5%, the combustion rate decreases by 37%. Similarly, the decreasing of the combustion rate will affect the energy input significantly reduced. Resulting from this, you will encounter a severe slag in the lower part of the incision.
To solve this issue, operators can use a conventional taper nozzle in traditional laser cutting technology. Besides, adding preheating flame around the cutting area may also solve this issue. Also, adding auxiliary oxygen flow around the cutting oxygen flow can meet the solution.
One of the most widely used automation techniques in the world is CNC laser cutting. As a result, we must be aware of any technical problems during the laser cutting process. We propose that you look over all of the technical issues again and strive to explain the science behind them.