In order to meet the requirements of functionality and appearance, the design of sheet metal should ensure simplicity in the stamping process, ease of mold fabrication, high-quality stamping results, and dimensional stability. Once the drawings are obtained, different methods such as laser cutting, CNC punching, shearing, and mold cutting can be chosen based on the unfolding diagram and batch requirements. The appropriate unfolding is then created according to the drawings.
CNC punching may result in significant burrs at the edges due to the influence of the tooling, especially when processing irregularly shaped workpieces and holes. Post-processing is required to remove the burrs, which may also affect the precision of the workpiece. Laser cutting, on the other hand, has no tooling limitations and produces smooth sections, making it suitable for processing irregularly shaped workpieces. However, it may be time-consuming for small workpiece processing. Placing the workbench next to the CNC machine and laser cutter facilitates the placement of the sheet metal for processing, reducing the effort of lifting the sheet.
Some usable scraps can be placed in designated areas to provide material for trial bending. After the workpiece is cut, it is necessary to trim the edges, remove burrs, and adjust the contact points (polishing treatment). A flat file is used to trim the contact points with the tool, while a grinding machine is used for workpieces with larger burrs. For small internal hole contact points, the corresponding small file is used to ensure a pleasing appearance. The trimming of the shape also ensures proper positioning during bending, allowing the workpiece to rest consistently on the bending machine and ensuring consistent dimensions among the batch of products.
After the cutting process, the workpiece proceeds to the next processing step based on the requirements. These steps may include bending, riveting, flanging, tapping, spot welding, embossing, and sectioning. In some cases, it is necessary to prioritize the processing of embossing and sectioning using molds to avoid interference with subsequent operations. For workpieces with hooks on the upper cover or lower shell, pre-processing is required before bending to ensure proper welding.
During bending, the selection of tools and die slots is determined based on the dimensions and material thickness specified in the drawings, to avoid deformation caused by collisions between the product and the tool. The selection of the upper die is crucial (different models may be used for the same product), while the selection of the lower die is based on the thickness of the sheet metal. The bending sequence is then determined, typically starting from the inside to the outside, from small to large, and from special shapes to general shapes. For workpieces that require edge folding, the workpiece is first bent to 30°-40° and then flattened using a specific tool to achieve the desired result.
When riveting, it is important to select the appropriate mold based on the height of the screw and adjust the pressure of the press machine to ensure that the screw and the workpiece surface are aligned, avoiding loose or over-pressed screws that may lead to product rejection.
Welding methods include argon arc welding, spot welding, CO2 shielding welding, and manual arc welding. For spot welding, the welding position of the workpiece should be considered. In mass production, the use of positioning fixtures ensures accurate spot welding positions.
To ensure a strong weld, protrusions are created on the workpiece to ensure uniform contact with the flat plate before electric welding, ensuring consistent heating of each point and determining the welding position. Proper adjustment of pre-pressing time, holding time, maintenance time, and rest time is necessary to secure a solid spot weld. After spot welding, welding scars may appear on the surface of the workpiece, which should be treated with a grinding machine. Argon arc welding is mainly used for connecting large workpieces or for edge treatment, achieving a smooth and polished surface. Heat generated during argon arc welding may cause workpiece deformation, which requires post-processing with grinding and polishing machines, especially for edge treatment.
Surface Treatment in Post-Processing of Workpieces
After completing bending, riveting, and other processes, workpieces require surface treatment. The surface treatment methods vary depending on the type of sheet metal. After cold plate processing, electroplating is generally performed. After electroplating, no spray coating is applied. Instead, phosphating treatment is carried out, followed by spray coating. For electroplated sheet metal, the surface is cleaned and degreased before spray coating. Stainless steel sheets (including mirror panels, matte panels, and brushed panels) can undergo brushing treatment before bending, eliminating the need for spray coating. If spray coating is required, the surface needs to be brushed to create a textured finish. Aluminum sheets are typically subjected to oxidation treatment, with different oxidation base colors chosen based on the desired spray coating color.
Common options include black and natural oxidation. Aluminum sheets that require spray coating undergo chromate oxidation treatment before the coating is applied. This pre-treatment ensures a clean surface, significantly improves coating adhesion, and greatly enhances the corrosion resistance of the coating. The cleaning process involves hanging the workpieces on a production line, first passing through a cleaning solution (alloy degreaser), then through clean water, followed by a spray area, and finally through a drying area before removing the workpieces from the production line.
After the pre-treatment, the workpieces enter the spray coating process. When spray coating is required after assembly, threads or certain conductive holes need to be protected. Threads can be covered with soft rubber rods or screwed in with screws, while conductive protection requires the use of high-temperature adhesive tape. For mass production, specific fixtures are used for positioning and protection to prevent overspray inside the workpieces. Nuts (flanges) visible on the outer surface of the workpiece are protected with screws to avoid the need for re-threading after spray coating.
Some large-scale workpieces also require protective fixtures. When workpieces are not assembled during spray coating, areas that do not require coating are covered with high-temperature adhesive tape and paper. Nuts (screws) exposed on the surface are protected with screws or high-temperature rubber. The same method is used to protect nuts (screws) when both sides of the workpiece are being spray coated. Small workpieces are bundled together with lead wires or paper clips before spray coating. For workpieces with high surface requirements, dust scraping is performed before spray coating. Special high-temperature adhesive stickers are used to protect grounding symbols on certain workpieces. During the spray coating process, the workpieces are hung on the production line, and compressed air is used to blow away any dust adhering to the surface. The spray coating is applied in the spray area, followed by the workpieces moving through the drying area along the production line. Finally, the coated workpieces are removed from the production line.
There are two types of spray coating: manual and automatic, which require different fixtures.
After spray coating, the workpieces go through the assembly process. Before assembly, the protective stickers used during spray coating are removed, and it is ensured that no paint or powder is scattered into the threaded holes. Throughout the process, gloves are worn to prevent dust from adhering to the workpieces, and in some cases, an air gun is used to clean the workpieces. After assembly, the workpieces are ready for packaging. They are inspected and then placed in specialized packaging bags for protection. If there is no specialized packaging, bubble wrap or other materials are used. Before packaging, the bubble wrap is cut to the appropriate size to avoid the need for cutting while packaging, which would slow down the process. For large-scale production, custom-made packaging boxes, bubble bags, cushioning pads, trays, wooden boxes, etc., are used. After packaging, the workpieces are placed in cardboard boxes, and corresponding finished or semi-finished product labels are attached to the boxes.
Quality of Sheet Metal Parts
In addition to strict requirements during the production process, the quality of sheet metal parts needs to be independently inspected. Firstly, dimensional checks are conducted according to the drawings, and secondly, the appearance quality is strictly controlled. Any parts that do not meet the dimensional requirements are either reworked or scrapped. The appearance should be free from scratches or marks, and inspections are carried out for color difference, corrosion resistance, and adhesion after spray coating. This helps identify errors in the unfolding diagram, bad habits during the production process, and process errors such as programming errors in numerical punching or mold errors.
1. Scope of Application
1.1 These guidelines apply to the shearing of materials with straight edges made of various black metals and similar materials.
1.2 The materials to be sheared have a basic thickness of 0.5 to 6 millimeters and a maximum width of 2500 millimeters.
2. Materials
2.1 The materials should meet the technical requirements.
2.2 The materials used are cold-rolled steel sheets, and severe abrasions, scratches, impurities, or rust spots on the surface are not allowed.
3. Equipment, Process Equipment, and Tools
3.1 Shears, clamps, oil cans, screwdrivers, hammers.
3.2 Vernier calipers, outside micrometers, steel rulers, steel tape measures, squares, scribes.
4. Process Preparation
4.1 Familiarize yourself with the drawings and relevant process requirements, and fully understand the geometric shape and dimensional requirements of the processed parts.
4.2 Obtain materials according to the specifications required by the drawings and check if the materials meet the process requirements.
4.3 To reduce consumption and improve material utilization, calculate the nesting method reasonably.
4.4 Neatly stack qualified materials next to the machine tool.
4.5 Lubricate the oil holes of the shearing machine.
4.6 Check the sharpness and secure fastening of the shearing machine blades, and adjust the blade clearance according to the thickness of the sheet metal.
CNC punching may result in significant burrs at the edges due to the influence of the tooling, especially when processing irregularly shaped workpieces and holes. Post-processing is required to remove the burrs, which may also affect the precision of the workpiece. Laser cutting, on the other hand, has no tooling limitations and produces smooth sections, making it suitable for processing irregularly shaped workpieces. However, it may be time-consuming for small workpiece processing. Placing the workbench next to the CNC machine and laser cutter facilitates the placement of the sheet metal for processing, reducing the effort of lifting the sheet.
Some usable scraps can be placed in designated areas to provide material for trial bending. After the workpiece is cut, it is necessary to trim the edges, remove burrs, and adjust the contact points (polishing treatment). A flat file is used to trim the contact points with the tool, while a grinding machine is used for workpieces with larger burrs. For small internal hole contact points, the corresponding small file is used to ensure a pleasing appearance. The trimming of the shape also ensures proper positioning during bending, allowing the workpiece to rest consistently on the bending machine and ensuring consistent dimensions among the batch of products.
After the cutting process, the workpiece proceeds to the next processing step based on the requirements. These steps may include bending, riveting, flanging, tapping, spot welding, embossing, and sectioning. In some cases, it is necessary to prioritize the processing of embossing and sectioning using molds to avoid interference with subsequent operations. For workpieces with hooks on the upper cover or lower shell, pre-processing is required before bending to ensure proper welding.
During bending, the selection of tools and die slots is determined based on the dimensions and material thickness specified in the drawings, to avoid deformation caused by collisions between the product and the tool. The selection of the upper die is crucial (different models may be used for the same product), while the selection of the lower die is based on the thickness of the sheet metal. The bending sequence is then determined, typically starting from the inside to the outside, from small to large, and from special shapes to general shapes. For workpieces that require edge folding, the workpiece is first bent to 30°-40° and then flattened using a specific tool to achieve the desired result.
When riveting, it is important to select the appropriate mold based on the height of the screw and adjust the pressure of the press machine to ensure that the screw and the workpiece surface are aligned, avoiding loose or over-pressed screws that may lead to product rejection.
Welding methods include argon arc welding, spot welding, CO2 shielding welding, and manual arc welding. For spot welding, the welding position of the workpiece should be considered. In mass production, the use of positioning fixtures ensures accurate spot welding positions.
To ensure a strong weld, protrusions are created on the workpiece to ensure uniform contact with the flat plate before electric welding, ensuring consistent heating of each point and determining the welding position. Proper adjustment of pre-pressing time, holding time, maintenance time, and rest time is necessary to secure a solid spot weld. After spot welding, welding scars may appear on the surface of the workpiece, which should be treated with a grinding machine. Argon arc welding is mainly used for connecting large workpieces or for edge treatment, achieving a smooth and polished surface. Heat generated during argon arc welding may cause workpiece deformation, which requires post-processing with grinding and polishing machines, especially for edge treatment.
Surface Treatment in Post-Processing of Workpieces
After completing bending, riveting, and other processes, workpieces require surface treatment. The surface treatment methods vary depending on the type of sheet metal. After cold plate processing, electroplating is generally performed. After electroplating, no spray coating is applied. Instead, phosphating treatment is carried out, followed by spray coating. For electroplated sheet metal, the surface is cleaned and degreased before spray coating. Stainless steel sheets (including mirror panels, matte panels, and brushed panels) can undergo brushing treatment before bending, eliminating the need for spray coating. If spray coating is required, the surface needs to be brushed to create a textured finish. Aluminum sheets are typically subjected to oxidation treatment, with different oxidation base colors chosen based on the desired spray coating color.
Common options include black and natural oxidation. Aluminum sheets that require spray coating undergo chromate oxidation treatment before the coating is applied. This pre-treatment ensures a clean surface, significantly improves coating adhesion, and greatly enhances the corrosion resistance of the coating. The cleaning process involves hanging the workpieces on a production line, first passing through a cleaning solution (alloy degreaser), then through clean water, followed by a spray area, and finally through a drying area before removing the workpieces from the production line.
After the pre-treatment, the workpieces enter the spray coating process. When spray coating is required after assembly, threads or certain conductive holes need to be protected. Threads can be covered with soft rubber rods or screwed in with screws, while conductive protection requires the use of high-temperature adhesive tape. For mass production, specific fixtures are used for positioning and protection to prevent overspray inside the workpieces. Nuts (flanges) visible on the outer surface of the workpiece are protected with screws to avoid the need for re-threading after spray coating.
Some large-scale workpieces also require protective fixtures. When workpieces are not assembled during spray coating, areas that do not require coating are covered with high-temperature adhesive tape and paper. Nuts (screws) exposed on the surface are protected with screws or high-temperature rubber. The same method is used to protect nuts (screws) when both sides of the workpiece are being spray coated. Small workpieces are bundled together with lead wires or paper clips before spray coating. For workpieces with high surface requirements, dust scraping is performed before spray coating. Special high-temperature adhesive stickers are used to protect grounding symbols on certain workpieces. During the spray coating process, the workpieces are hung on the production line, and compressed air is used to blow away any dust adhering to the surface. The spray coating is applied in the spray area, followed by the workpieces moving through the drying area along the production line. Finally, the coated workpieces are removed from the production line.
There are two types of spray coating: manual and automatic, which require different fixtures.
After spray coating, the workpieces go through the assembly process. Before assembly, the protective stickers used during spray coating are removed, and it is ensured that no paint or powder is scattered into the threaded holes. Throughout the process, gloves are worn to prevent dust from adhering to the workpieces, and in some cases, an air gun is used to clean the workpieces. After assembly, the workpieces are ready for packaging. They are inspected and then placed in specialized packaging bags for protection. If there is no specialized packaging, bubble wrap or other materials are used. Before packaging, the bubble wrap is cut to the appropriate size to avoid the need for cutting while packaging, which would slow down the process. For large-scale production, custom-made packaging boxes, bubble bags, cushioning pads, trays, wooden boxes, etc., are used. After packaging, the workpieces are placed in cardboard boxes, and corresponding finished or semi-finished product labels are attached to the boxes.
Quality of Sheet Metal Parts
In addition to strict requirements during the production process, the quality of sheet metal parts needs to be independently inspected. Firstly, dimensional checks are conducted according to the drawings, and secondly, the appearance quality is strictly controlled. Any parts that do not meet the dimensional requirements are either reworked or scrapped. The appearance should be free from scratches or marks, and inspections are carried out for color difference, corrosion resistance, and adhesion after spray coating. This helps identify errors in the unfolding diagram, bad habits during the production process, and process errors such as programming errors in numerical punching or mold errors.
1. Scope of Application
1.1 These guidelines apply to the shearing of materials with straight edges made of various black metals and similar materials.
1.2 The materials to be sheared have a basic thickness of 0.5 to 6 millimeters and a maximum width of 2500 millimeters.
2. Materials
2.1 The materials should meet the technical requirements.
2.2 The materials used are cold-rolled steel sheets, and severe abrasions, scratches, impurities, or rust spots on the surface are not allowed.
3. Equipment, Process Equipment, and Tools
3.1 Shears, clamps, oil cans, screwdrivers, hammers.
3.2 Vernier calipers, outside micrometers, steel rulers, steel tape measures, squares, scribes.
4. Process Preparation
4.1 Familiarize yourself with the drawings and relevant process requirements, and fully understand the geometric shape and dimensional requirements of the processed parts.
4.2 Obtain materials according to the specifications required by the drawings and check if the materials meet the process requirements.
4.3 To reduce consumption and improve material utilization, calculate the nesting method reasonably.
4.4 Neatly stack qualified materials next to the machine tool.
4.5 Lubricate the oil holes of the shearing machine.
4.6 Check the sharpness and secure fastening of the shearing machine blades, and adjust the blade clearance according to the thickness of the sheet metal.
