Introduction
Sheet metal processing refers to the cold processing of metal plates below 6mm. It can be divided into two categories: stamping processing, suitable for mass production, and CNC sheet metal processing, suitable for small batch production. This post focuses on analyzing and improving cutting waviness during sheet metal laser cutting and blanking in small batch production.
Sheet metal processing has a wide range of applications in industries such as chassis and cabinets, household appliances, hardware products, instruments and meters, billboards, lamps and machine manufacturing. It is characterized by fast processing speed, short cycle, small surface deformation and ability to process various materials without additional tools.
In recent years, our company has developed the optical disc library industry to meet the market demand for small batches and diverse products. The central part of the optical disc library case is the internal action component, which plays a crucial role in the overall performance of the mechanism. The process dimension accuracy of the core sheet metal products inside the cabinet requires ±0.1mm.
To ensure processing accuracy, our company uses Amada's optical fiber laser stamping machine for laser cutting and blanking of sheet metal products, which has a processing accuracy of ±0.07mm/1000mm.
However, during the laser cutting and erasing process, abnormal cutting phenomena such as cutting waviness and cutting burrs may occur, leading to product defects and increased processing costs.
Through comprehensive analysis and comparison of defective products, it was found that cutting waviness mainly occurs in larger products, with a defect rate of about 10%. In contrast, smaller products have a lower defect rate of less than 1%. To reduce production losses and processing costs, it is essential to analyze and study the laser cutting process.
Cutting and erasing status
The composite machine is used for laser cutting and stamping of sheet metal, with the machine clamp holding the sheet metal and moving along the X and Y directions, as illustrated in Fig. 1, which shows the sheet metal processing equipment. product and the processing area.
However, during continuous processing, the local tension of the plate is released, gradually weakening its strength and causing the plate to wobble during movement. As a result, ripples occur in the laser cutting, leading to poorly processed products. The size of the cutting corrugation is also affected by several factors, such as the product processing direction, the initial processing position, and the order of product removal, as shown in Figure 2 and Figure 3.
Furthermore, cutting large products results in a greater release of tension in the sheet, causing the sheet to shake even more during the cutting of the remaining pieces. This results in ripple cutting, leading to higher processing costs and material waste.
To minimize such occurrences, it is essential to ensure the stability and resistance of the sheet during the cutting process, especially when dealing with large products that require longer processing times.
Fig. 1 Processing equipment and processing area
Fig. 2 cutting corrugation state 1
Fig. 3 cutting corrugation state 2
Factors influencing the cut of the curl
Product processing starting position
During the cutting process, the initial position of the products plays a crucial role in generating cutting waves. Typically, machining begins at the end farthest from the clamp or the end closest to the clamp.
If the product is processed from a position away from the gripper, as shown in Fig. 4, the plate at the end of the gripper can be finally cut. This approach can ensure that the tension of the plate is not released early, which in turn ensures the strength and stability of the plate during movement, ultimately preventing the occurrence of cutting ripples.
On the other hand, when the product is processed from a position close to the gripper, as shown in Figure 5, plate tension is not significantly compromised at the beginning of processing, so cutting ripples are less likely to occur. However, continuous cutting of the plate near the end of the clamp will gradually release tension from the plate, leading to an unstable plate during movement.
When processing gradually moves away from the clamp, peripheral products are likely to have cutting ripples due to insufficient plate strength. Therefore, during programming, it is essential to ensure that products are cut starting from the far end of the gripper and then progressively towards the end of the gripper. This approach guarantees the strength of the plate and eliminates the generation of cutting waves.
Fig. 4 Good initial processing position
Fig. 5 The initial processing position is bad
Cutting point position and machining direction
During the sheet metal cutting process, the entry point where cutting starts will naturally become the exit point when cutting is completed.
Selecting a suitable entry point can reduce the likelihood of cutting ripples.
At the beginning of the cutting process, due to the good strength of the sheet, the entry point and cutting direction do not have much impact. However, as the cutting process approaches its end, the entry point and direction of cutting become crucial in determining whether cutting ripples will be produced in the remaining products.
To avoid generating cutting waves, make sure that the products near the end of the clamp have sufficient strength.
If the entry point is selected in the middle of the product and cutting is done clockwise or counterclockwise, the bottom of the product will be cut first. This results in the release of tension from the plate, which reduces the strength and stability of the product. Consequently, local cutting ripples may occur, as shown in Figure 6.
If the entry point is selected at the lower end, the product closest to the clamp end will be cut last, which means that plate tension is not released early, making the process more stable and reducing the likelihood of ripples occurring. in the cut, as shown in Figure 7.
When programming the cutting process, ensure that the entry point and cutting direction are selected so that the product is finally cut close to the end of the clamp.
The shorter the distance covered during the cutting process, the more cutting ripples can be avoided to a certain extent. Of course, when selecting the entry point at the bottom of the product, consider whether the cutting direction is clockwise or counterclockwise.
Fig. 6 The position of the cutting point is bad
Fig. 7 the position of the cutting point is good
Clamp fixing position
The function of the clamps is to hold the plate in place and allow it to move in the X and Y directions according to the processing program. They guarantee the stability of the board during the processing operation. Therefore, it is essential to evenly distribute the positions of the clamps, which will avoid unstable shaking of the plates caused by the deflection of the clamps to one side and the generation of cutting ripples.
Figure 8 shows a comparison of the clamp positions.
Although the positioning of the clamps may impact the cutting waviness, this factor can be avoided during the operation process.
Fig. 8 Clamp fixing position
Product removal sequence
During the production process, the TK manipulator is sometimes used to assist in taking out cut products, which can save human and material resources and achieve fully automated production equipment. However, when using the TK manipulator to remove products, it is essential to pay attention to controlling the product removal sequence to avoid weakening the resistance and agitation of the materials that could cause ripples in the cut.
Taking products first from both ends of the board and then from the middle may lead to the release of tension at both ends of the board, resulting in insufficient strength of the board. When the processing program reaches the middle of the plate, the plate may shake due to insufficient resistance, causing cutting ripples in the products and resulting in high rates of product defects and processing losses, as shown in Figure 9.
To avoid this problem, it is essential to remove the products successively from the side away from the tweezers. This ensures that the stress concentration of the plate at the processing position is well distributed and the movement is stable, preventing the occurrence of cutting ripples, as shown in Figure 10.
Therefore, during processing and programming, it is important to ensure that products are removed sequentially from the far end of the gripper to maintain plate strength and avoid shaking during movement, thus avoiding the generation of cutting ripples.
Fig. 9 poor product removal sequence
Fig. 10 good product removal sequence
Conclusion
The factors influencing the above research are based on an analysis of the cutting ripples at this stage.
The generation of cutting ripples is not influenced by a single factor, but by the combined effects of several factors, including size, weight, processing speed and others.
To avoid the generation of cutting ripples, comprehensive consideration of all factors during the programming process is necessary to minimize the possibility of cutting ripples.
