During the manufacturing process, sheet metal parts will have varying degrees of sharp edges and burrs. If they exceed a certain limit, they can cause negative impacts on various aspects such as production, transportation, quality, performance, appearance and even cause damage to those who use the product.
For example, sharp edges and burrs can affect the processing and positioning of the assembly, causing scratches to the surface coating and causing paint and rust damage. Additionally, they can cause damage to processors' hands and other body parts.
As people's demands on products continue to improve, the potential damage caused by uncontrolled sharp edges and burrs is attracting more and more attention.
Causes of Sharp Edges and Burrs on Sheet Metal Parts
Sharp edges are plane intersections that occur naturally during processing.
Sheet punching burr is a step in the separation process that occurs after the material undergoes elastic and plastic deformation during cutting or shearing.
As the dipping process begins, cracks appear near the cutting edge of the die.
As the amount of cut material increases, upper and lower cracks continue to spread through the material.
When the cutting edge gap is set correctly, the top and bottom cracks overlap, causing the sheet metal to typically crack and separate.
If the cutting edge clearance is not adjusted correctly, the upper and lower cracks will not align, resulting in drill burrs.
The main causes of burrs in laser cutting of sheet metal parts are:
During the laser cutting process, the high energy of the laser beam causes the cutting part of the part to quickly vaporize and evaporate, allowing cutting to occur.
To ensure good cutting quality, residual slag on the surface must be removed with auxiliary gas. If this step is ignored, burrs will form on the cutting surface as the slag cools.
Furthermore, equipment precision and processing parameters not set correctly can also contribute to burr formation.
Another important factor in the formation of burrs is the increase in microconnections between the tool and the part, a result of the demands of the punching and shearing process.
The need to control sharp edges and burrs
Sharp edges and burrs generated during sheet metal processing can have a significant impact on the surface quality and appearance of the final product, as well as pose a safety risk. To mitigate these effects, it is important to research ways to suppress or reduce burrs to ensure smooth and safe production. This involves finding ways to eliminate or fundamentally minimize the presence of sharp edges and burrs.
Measures to control sharp edges and burrs
Measures to control sharp edges and burrs can be divided into two categories based on processing technology:
The first category involves designing processes to minimize sharp edges and burrs, including controlling burr heights within acceptable limits.
In the production of stainless steel sheet metal parts for elevators, the product design team considers burr formation and removal mechanisms during the design phase to minimize the occurrence of burr. This may include:
- Using burr-free design techniques such as adding grooves, cuts, rounded corners, etc. to edges where burrs may occur
- Modify part geometry to make burrs nonfunctional or easier to remove.
The second category involves deburring technologies, such as the following measures in punching and shearing production:
(1) Selecting a reasonable tool clearance during punching and shearing is a crucial factor in reducing burrs in the final product. The size of the edge gap should be based on the thickness and strength of the material being punched and sheared, and can be determined using reference tables.
Table 1 Numerical reference of the initial bilateral gap Z of the blanking matrix
| Thickness | 08,10,35,Q235 | 16 minutes | 40,50,1Cr18NiuTi | |||
|---|---|---|---|---|---|---|
| Zmin | Zmax | Zmin | Zmax | Zmin | Zmax | |
| 0.50 | 0.040 | 0.060 | 0.040 | 0.060 | 0.040 | 0.060 |
| 0.70 | 0.064 | 0.092 | 0.064 | 0.092 | 0.064 | 0.092 |
| 0.80 | 0.072 | 0.104 | 0.072 | 0.104 | 0.072 | 0.104 |
| 0.90 | 0.090 | 0.126 | 0.090 | 0.126 | 0.090 | 0.126 |
| 1.00 | 0.100 | 0.140 | 0.100 | 0.140 | 0.100 | 0.140 |
| 1.20 | 0.126 | 0.180 | 0.132 | 0.180 | 0.132 | 0.180 |
| 1.50 | 0.132 | 0.240 | 0.170 | 0.240 | 0.170 | 0.230 |
| 1.75 | 0.220 | 0.320 | 0.220 | 0.320 | 0.220 | 0.320 |
| 2:00 | 0.246 | 0.360 | 0.260 | 0.380 | 0.260 | 0.380 |
| 2.50 | 0.360 | 0.500 | 0.380 | 0.540 | 0.380 | 0.540 |
| 3:00 | 0.460 | 0.640 | 0.480 | 0.660 | 0.480 | 0.660 |
| 3.50 | 0.540 | 0.740 | 0.580 | 0.780 | 0.580 | 0.780 |
(2) The roughness and wear of the tool cutting edge during punching and cutting can also contribute to the formation of burrs.
It is important to control the roughness and wear of the cutting edge. If the edge becomes worn or damaged, it will become rounded and the gap will increase due to side wear, leading to increased burrs.
Tools typically go through three stages of wear: initial wear, normal wear, and abnormal wear. Ideally, tools should be replaced before they reach the stage of abnormal wear. However, in many cases, the allowable burr height is reached during normal wear due to product accuracy requirements. At this point, replacement or rectification must be carried out.
Regular maintenance and tool tip sharpening can reduce burrs, reduce shear force on the machine, and extend the life of the machine and tools.
(3) Proper choice of processing tools, equipment and processing conditions is also important.
The tool material must have good wear resistance and high hardness, because the higher the hardness of the cutting edge, the lower the burr height will be.
The mold structure must incorporate a high-precision mold guiding device to ensure reasonable clearance during punching, thereby reducing burrs.
In terms of the accuracy of processing equipment, the higher the static and dynamic accuracy, the lower the probability of burrs on the board.
The use of lubricating oil can reduce the friction between the cutting edge of the tool and the material being processed, prevent temperature rises caused by shear deformation, and prevent the material from adhering to the cutting edge of the tool. Therefore, good lubrication conditions can help reduce the occurrence of burrs.
In laser cutting production, the following measures can also be taken to reduce burrs:
(1) Select high-quality and high-purity cutting auxiliary gas.
(2) Choose appropriate cutting parameters such as focus position, laser power, air pressure, feeding speed, nozzle distance, etc. to optimize cut quality and minimize or eliminate burrs.
(3) Adjust the static and dynamic precision of the machine to ensure stability.
As for microconnections between tool contacts and parts in punching and shearing, it is best to avoid their use if possible. If they are used, they must be removed manually or with a machine.
Control measures for sharp edges and burrs of stainless steel sheet metal parts of elevators
In addition to implementing measures to minimize sharp edges and burrs during the punching and shearing process, for stainless steel sheet parts in elevators, different deburring processes are prioritized based on the risk of sharp edges and burrs, divided into high risk, medium risk, and low risk.
These priorities are taken into account when organizing the deburring processes after cutting. Some products may need to be deburred before being transferred for further processing, while others may be sent directly to product assembly.
The choice of deburring processes is made taking into account product quality, production efficiency and cost, taking into account economic viability.
Currently, although there are many techniques for removing sharp edges and burrs on sheet metal parts, most elevators use mechanical methods for their stainless steel sheet metal parts.
For large to medium volume parts such as car walls, hallway doors and car doors, sharp edges and burrs are typically removed through mechanical grinding before bending. For single-piece and small batch products that have already been bent and formed, manual deburring methods are used.
Typical Deburring Technology of Elevator Stainless Steel Sheet Metal Parts
Figure 1 represents an angle grinder located after the Salvagnini punching and shearing center. It is mainly used for deburring corridor doors, car doors and car walls in mass production without bending.
Fig. 1 Deburring machine arranged after the punching and shearing processing center
Figure 2 shows a brush deburring machine located after the laser cutting machine. It is mainly used for medium-sized batches such as car front walls, doors and roofs, to remove burrs from products that have not been bent after laser cutting.
Figure 2 Angle grinder with brush arranged behind the laser cutting machine
Figure 3 shows a manual deburring tool. This tool is mainly used for small batches of products that cannot be deburred by the machine, such as door heads that have been drilled and shaped.
Figure 3 Manual deburring
When selecting a deburring technology, there are several factors to consider, including existing production conditions, the technical proficiency of workers and your operating practices.
An appropriate and reasonable deburring process is crucial to improving product quality and reducing manufacturing costs while ensuring that quality is maintained.
The basic principle for choosing a deburring process is to ensure low cost and maintain quality.
The selection of a deburring process requires careful consideration as it has a significant impact on the cost of investment in plant and equipment, environmental protection and process equipment.
Final Words
The formation of sharp edges and burrs on sheet metal parts is a common problem in the punching and shearing process, and although it can be difficult to eliminate completely, it can be minimized. The reasons and control measures for their formation have been described, and the process of removing sharp edges and burrs from stainless steel sheet parts of elevators is also described.
Our engineers and technicians always strive to control the risks of sharp edges and burrs to a minimum while ensuring quality. By choosing the appropriate conditions, control measures and removal processes, we aim to maximize efficiency and minimize costs.
