1, The selection of materials for sheet metal processing includes cold-rolled sheet metal (SPCC), hot-rolled sheet metal (SHCC), galvanized sheet metal (SECC, SGCC), copper (CU), brass, purple copper, beryllium copper, aluminum plates (6061, 6063, hard aluminum, etc.), aluminum profiles, and stainless steel (mirror)
Surface, brushed surface, matte surface), depending on the different functions of the product, different materials are selected, generally considering the product's purpose and cost.
1. Cold rolled SPCC sheet is mainly used for electroplating and baking paint parts, with low cost, easy molding, and material thickness ≤ 3.2mm.
2. Hot rolled plate SHCC, material T ≥ 3.0mm, also uses electroplating and baking paint parts, with low cost but difficult to form, mainly using flat parts.
3. Galvanized sheet SECC, SGCC. SECC electrolytic plates are divided into N material and P material. N material is mainly not surface treated and has a high cost, while P material is used for spraying parts.
4. Copper; Mainly using conductive materials, the surface treatment is nickel plating, chromium plating, or no treatment, which is costly.
5. Aluminum plate; Generally, surface chromate (J11-A) is used for oxidation (conductive oxidation, chemical oxidation), which is costly. Silver plating and nickel plating are available.
6. Aluminum profiles; Materials with complex cross-sectional structures are widely used in various plug-in boxes. Surface treatment is the same as aluminum plate.
7. Stainless steel; Mainly used without any surface treatment, high cost.
2, To review the drawings and write the process flow of the parts, it is necessary to first understand the various technical requirements of the part drawings; The review of drawings is the most important step in writing the process flow of parts.
1. Check if the drawing is complete.
2. The relationship between the drawing and view, whether the annotations are clear and complete, and the units of dimension annotations.
3. Assembly relationship, key dimensions required for assembly.
4. Differences between old and new layouts.
5. Translation of foreign language images.
6. Conversion of table codes.
7. Feedback and handling of graphic issues.
8. Materials
9. Quality requirements and process requirements
10. The official release of drawings must be stamped with a quality control seal.
3, Unfolding precautions, the unfolding diagram is a plan view (2D) unfolded based on the part drawing (3D)
The unfolding method should be reasonable, convenient, and save materials and processing efficiency
2. Reasonably choose the gap and edge wrapping method, with a gap of 0.2 for T=2.0 or less, and a gap of 0.5 for T=2-3. The edge wrapping method uses long edges wrapped with short edges (for door panels)
3. Reasonably consider the tolerance of external dimensions: the negative deviation should be reduced to the bottom, and the positive deviation should be reduced by half; Hole size: The positive difference should be reduced to the bottom, and the negative difference should be reduced by half.
4. Burr direction
5. Draw a sectional view in the direction of tooth extraction, riveting, tearing, punching convex points (bags), and other positions
6. Check the material, plate thickness, and tolerance of the plate thickness
7. For special angles, the inner radius of the bending angle (usually R=0.5) needs to be determined by trial bending before unfolding
8. Areas that are prone to errors (similar asymmetry) should be highlighted
9. Enlarged images should be added for areas with larger sizes
10. Areas that require spray protection must indicate
4, The process flow of sheet metal processing may vary depending on the differences in the structure of the sheet metal parts, but generally does not exceed the following points.
1. Cutting: There are various ways of cutting, mainly including the following methods
① Cutting machine: It is the use of a cutting machine to cut simple pieces of strip material. It is mainly used for preparing and processing for mold cutting and forming, with low cost and accuracy below 0.2, but can only process strip or block materials without holes or cutting angles.
② Punch press: It is the use of a punch press to punch and shape various shapes of flat parts on a sheet metal after unfolding the parts in one or more steps. Its advantages are short labor time, high efficiency, high precision, low cost, suitable for large-scale production, but require mold design.
③ NC numerical control cutting, when NC cutting, the first step is to write a numerical control machining program. Using programming software, the drawn unfolded diagram is written into a program that can be recognized by the NC numerical drawing machine tool. According to these programs, it can punch various shapes of flat parts on the flat plate step by step, but its structure is affected by the tool structure, with low cost and accuracy of 0.15.
④ Laser cutting is the use of laser cutting to cut the structural shape of a large flat plate. Like NC cutting, a laser program needs to be written. It can cut various complex shaped flat plates 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 precision.
Fitter: countersunking, tapping, reaming, drilling. The countersunking angle is generally 120 ℃, used for pulling rivets, and 90 ℃ is used for countersunking screws and tapping British bottom holes.
Flanging: also known as hole drawing or flipping, it is to draw a slightly larger hole on a smaller base hole and then tap it. It is mainly used for sheet metal processing with relatively thin plate thickness to increase its strength and thread number, and avoid slipping. It is generally used for shallow flanging with normal hole circumference and relatively thin plate thickness. When the thickness is allowed to be reduced by 30-40%, a height 40-60% higher than the normal flanging height can be obtained. When the thickness is reduced by 50%, the maximum flanging height can be obtained. When the plate thickness is large, such as 2.0, 2.5, etc., it can be directly tapped.
Punch press: It is a processing process that uses molds to form. Generally, punch press processing includes punching, corner cutting, material dropping, punching convex hull (convex point), punching tearing, hole drawing, forming and other processing methods. Its processing requires corresponding molds to complete the operation, such as punching material dropping mold, convex hull mold, tearing mold, hole drawing mold, forming mold, etc. The operation mainly pays attention to the position and directionality.
Riveting: As far as our company is concerned, riveting mainly includes riveting nuts, screws, and fasteners, which are operated by hydraulic riveting machines or punching machines to rivet them onto sheet metal parts. There are also riveting methods, and attention should be paid to directionality.
Bending; Bending is the process of folding 2D flat parts into 3D components. Its processing requires a folding bed and corresponding bending molds to complete, and it also has a certain bending sequence. The principle is to fold the next blade that does not interfere first, and fold the one that will interfere later.
The number of bends is 6 times the thickness of the plate below T=3.0mm to calculate the groove width, such as: T=1.0,V=6 .0 F=1.8, T=1.2,V=8,F=2.2,T=1.5,V=10,F=2.7,T=2.0,V=12, F=4.0
Classification of folding bed molds, straight knife, curved knife (80 ℃, 30 ℃)
When bending aluminum plates, if there are cracks, the width of the lower mold slot can be increased to increase the upper mold R (annealing can avoid cracks)
Precautions for bending: Firstly, the drawing requires the thickness and quantity of the board; II bending direction III bending angle; IV. Bending size; The appearance and chrome plated parts must not have creases.
The relationship between bending and riveting processes generally involves riveting first and then bending. However, if there are materials that interfere after riveting, they need to be folded first and then pressed. Some processes require bending, riveting, and then bending again.
Welding: Welding definition: The distance between the atoms and molecules of the welded material and the Jingda lattice forms a whole
① Category: a Melting welding: argon arc welding, CO2 welding, gas welding, manual welding b Pressure welding: spot welding, butt welding, impact welding c Brazing: electric chromium welding, copper wire
② Welding methods: a CO2 gas shielded welding b argon arc welding c point welding, etc. d robot welding
The selection of welding methods depends on actual requirements and materials. 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 labor hours, improve work efficiency and welding quality, and reduce work intensity.
③ Welding symbols: Δ angle welding, Д, I-type welding, V-type welding, single-sided V-type welding (V) with blunt edge V-type welding (V), spot welding (O), plug welding or groove welding (π), rolled edge welding (χ), single-sided V-type welding with blunt edge (V), blunt U-type welding, blunt J-type welding, bottom sealing welding, butt welding
④ Arrow lines and connectors
⑤ Welding deficiency and preventive measures: Spot welding: If the strength is not enough, convex points can be made to impose welding area. CO2 welding: high productivity, low energy consumption, low cost, strong rust resistance. Argon arc welding: shallow dissolution, slow dissolution speed, low efficiency, high production cost, with tungsten inclusion defects, but has the advantage of good welding quality. It can weld non-ferrous metals such as aluminum, copper, magnesium, etc.
⑥ Reasons for welding deformation:
Insufficient preparation before welding, additional fixtures are needed
Improvement process for welding fixture defects
Poor welding sequence
⑦ Welding deformation correction method:
Flame Effect Correction Method
Vibration method
Hammer
Artificial time efficiency method
