Sheet metal processing process flow
With the development of today's society, the sheet metal industry has also developed rapidly. Nowadays, sheet metal involves various industries. For any sheet metal part, it has a certain processing process, which is called the process flow. To understand the sheet metal processing process, the first thing to know is the selection of sheet metal materials.



1、 Material selection.
The materials commonly used in sheet metal processing include cold-rolled sheets, hot-rolled sheets, galvanized sheets, brass, purple copper, beryllium copper, aluminum sheets, aluminum profiles, stainless steel, etc. The selection of materials varies depending on the product's function, and generally needs to be considered from the perspective of the product, its purpose, and cost.
1. Cold rolled sheet: mainly used for electroplating and painting parts, low cost, easy to form, material thickness ≤ 3.2mm.
2. Hot rolled plate: material T ≥ 3.0mm, also used for electroplating and painting parts, low cost, but difficult to form, mainly using flat parts.
3. Galvanized sheet SECC, SGCC. SECC electrolytic plates are divided into N material, P material, and N material, mainly without surface treatment, with high cost. P material is used for spraying parts.
4. Copper: Mainly used for conductive materials, its surface treatment is nickel plating, chromium plating, or no treatment, with high cost.
5. Aluminum plate: Generally, surface chromate (J11-A) is used for oxidation (conductive oxidation, chemical oxidation), with high cost, and can be plated with silver or nickel.
6. Aluminum profile: a component with a complex cross-sectional structure, widely used in various plug-in boxes, with the same surface treatment as aluminum plates.
7. Stainless steel: mainly used without any surface treatment, with high cost.



2、 Drawing review is the most important step in writing the process flow of a part, as it involves understanding the various technical requirements of the part drawing.
1. Check if the drawings are complete;
2. The relationship between drawings and views, whether the annotations are clear and complete, and whether the dimension units are marked;
3. Assembly relationship, key dimensions required for assembly;
4. Differences between new and old layouts;
5. Translation of foreign language images;
6. Table code conversion;
7. Feedback and handling of graphic problems;
8. Materials;
9. Quality and process requirements;
10. The official release of the drawings must be stamped with a quality control seal.



3、 Notes for unfolding: The unfolding diagram is a flat view (2D) developed based on the part drawing (3D)
1. The unfolding method should be appropriate, convenient to save materials and processability;
2. Reasonably choose the gap and edge wrapping method, with a gap of 0.2 for T=2.0 or below and a gap of 0.5 for T=2-3. The edge wrapping method adopts a long edge wrapping short edge;
3. Fair consideration of tolerance, shape and size: negative deviation to the end, positive deviation to half; Hole size: positive deviation to the bottom, negative deviation to half;
4. Burr direction;
5. Draw a sectional view in the direction of tooth extraction, riveting, tearing, and punching convex points (packages);
6. Verify the material, plate thickness, and use the plate thickness tolerance;
7. Special angles, the inner radius of the bending angle (generally R=0.5) needs to be tested and unfolded;
8. Emphasis should be placed on highlighting areas that are prone to making mistakes (similar and divergent errors);
9. Enlarge the image for areas with larger dimensions;
10. Areas that require spray protection must be indicated.



4、 The process flow of sheet metal processing may vary depending on the structural differences of the sheet metal parts, but the overall process does not exceed the following points:
1. Cutting: There are various cutting methods, mainly including the following
① Scissor bed: It is a machine that uses scissors to cut simple materials and parts. It is mainly used for preparing and processing the mold for material cutting and forming. It has low cost and accuracy below 0.2, but can only process strip or block materials without holes or cutting corners.
② Punching machine: It is a type of machine that uses a punching machine to unfold parts on a sheet metal in one or more steps to form various shaped parts. Its advantages include short working hours, high efficiency, high accuracy, low cost, and the need to design molds for mass production.
③ NC numerical control cutting: When NC cutting, the first step is to write a numerical control machining program. Using programming software, the unfolded diagram is written into a program that can be recognized by the NC numerical drawing machine tool. Based on these programs, each structure of the flat part is punched step by step on the flat plate. However, its structure is affected by the tool structure, with low cost and an accuracy of 0.15.
④ Laser cutting: Using laser cutting method, the structural shape of the flat plate is cut out on a large flat plate. Similar to NC cutting, a laser program needs to be written. It can cut various complex shaped flat parts with high cost and accuracy of 0.1
⑤ Sawing machine: mainly used for aluminum profiles, square tubes, drawing tubes, round bar materials, etc., with low cost and low accuracy.
2. Flanging: also known as punching or flipping, it is the process of drawing a slightly larger hole on a smaller base hole, then tapping it. It is mainly processed using sheet metal with thinner plate thickness to increase its strength and thread number, avoiding slippage. It is generally used for shallow flanging with thinner plate thickness and normal hole circumference, and the thickness remains basically unchanged. When there is a thickness reduction of 30-40%, a height of 40-60% higher than the normal flanging height can be obtained. When using extrusion thinning by 50%, The maximum flange height can be obtained, and when the plate thickness is large, such as 2.0, 2.5 or above, it can be directly tapped.
3. Punching machine: It is a processing process that uses molds to form. Generally, punching machines process methods such as punching, corner cutting, material cutting, convex hull punching, tearing, hole drawing, and forming. The processing requires corresponding molds to complete the operation, such as punching and material cutting molds, convex hull molds, tearing molds, hole drawing molds, and forming molds. The operation mainly pays attention to position and directionality.
4. Riveting: For our company, riveting mainly includes riveting nuts, screws, and fasteners. It is controlled by hydraulic riveting machines or punches to rivet them onto sheet metal parts. There is also a method of expanding riveting, which requires attention to directionality.
5. Bending: Bending is the process of folding 2D flat parts into D parts. Its processing requires a bending machine and corresponding bending molds to complete, and it also has a certain bending sequence. The principle is to fold first without interference with the next tool, and then fold later if interference occurs.
6. Welding: Definition of welding: The atoms and molecules of the material being welded are separated by the Jingda lattice to form a whole
① Classification:
a: Melt welding: argon arc welding, CO2 welding, gas welding, manual welding
b: Pressure welding: spot welding, butt welding, collision welding
c: Brazing: electrochromic welding, copper wire
② Welding method:
a: CO2 gas shielded welding
b: Argon arc welding
c: Spot welding, etc
d: Robot welding
The selection of welding methods is based on the actual material requirements. Generally speaking, CO2 gas shielded welding is used for welding iron plates; Argon arc welding is used for welding stainless steel and aluminum plates. Robot welding can save time, improve work efficiency and welding quality, and reduce work intensity.
③ Welding symbols: Δ Corner welding; I-type welding; V-shaped welding; Unilateral V-shaped welding; V-shaped welding with blunt edges; Spot welding (O); Plug welding or slot welding (π); Curled edge welding（ χ）； Single sided V-shaped welding with blunt edges (V); U-shaped welding with blunt edges; J-shaped welding with blunt edges; Back welding; Welding.
④ Arrow lines and joints;
⑤ Welding defects and preventive measures;
Spot welding: If the strength is not enough, convex points can be made and the welding area can be forced;
CO2 welding: high production rate, low energy consumption, low cost, strong rust resistance;
Argon arc welding: shallow dissolution depth, slow dissolution speed, low efficiency, high production cost, with tungsten inclusion defects, but with the advantage of good welding quality, it can weld non-ferrous metals such as aluminum, copper, magnesium, etc.
⑥ Reasons for welding deformation:
a: Insufficient preparation before welding, additional fixtures need to be added;
b: Improvement process for welding fixture defects;
c: Poor welding sequence.
⑦ Welding deformation effect euthanasia:
a: Execution by flame effect;
b: Vibration method;
c: Hammering method;
d: Artificial time method.



Reading source: Manufacturer of flat plate faucets www.baolonghs.com