Sheet metal processing is called sheet metal processing. Specifically, such as making chimneys, iron drums, oil tanks, oil pots, ventilation pipes, elbows, gardens, funnels, etc. For plates, the main processes are cutting, bending, forming, welding, riveting and so on. This requires a certain knowledge of geometry. Sheet metal parts are sheet metal parts, that is, parts that can be processed by stamping, bending and drawing. The general definition is a part with constant thickness during machining.
Correspondingly, cold working of metals, such as castings, forgings, machined parts, etc., usually refers to metal cutting, that is, using cutting tools to remove excess metal layers from metal materials (blanks) or workpieces, so that the workpieces can obtain certain shape, dimensional accuracy and surface roughness. Such as turning, drilling, milling, planing, grinding and broaching. In metal technology, corresponding to hot working, cold working refers to the processing technology that causes metal plastic deformation below recrystallization temperature, such as cold rolling, cold drawing, cold forging, stamping, cold extrusion and so on. Cold working deformation resistance is large. When forming metal, work hardening can be used to improve the hardness and strength of the workpiece, but it will reduce the plasticity. Cold working is suitable for machining metal parts with small cross-section size and high requirements for machining size and surface roughness.
Common sheet metal parts processing process
1. Material selection: The commonly used materials for sheet metal processing are cold-rolled sheet (SPCC), hot-rolled sheet (SHCC), galvanized sheet (SGCC SECC), copper (CU) brass, red copper, beryllium copper, aluminum sheet (606 1, 6063, hard aluminum, etc. ), aluminum profile, stainless steel (.
1. The cold-rolled plate SPCC is mainly made of low-cost and easy-to-shape electroplated baked parts, and the material thickness is ≤ 3.2 mm ..
2. Hot-rolled SHCC, made of T≥3.0mm, is also baked by electroplating, with low cost, but difficult to form, and mainly uses flat parts.
3.SECC and SGCC galvanized sheets. SECC electrolytic plate is divided into N material and P material. N material is mainly without surface treatment and has high cost, while P material is used for spraying. 4. copper; Conductive materials are mainly used, and their surface treatment is nickel and chromium plating, or no treatment, which is costly.
5. aluminum plate; Generally, surface chromate (J 1 1-A) and oxidation (conductive oxidation and chemical oxidation) are used, which are costly, including silver plating and nickel plating.
6. Aluminum profiles; Materials with complex cross-sectional structure are widely used in various boxes. Surface treatment is the same as aluminum plate.
7. Stainless steel; Mainly used without any surface treatment, with high cost.
Second, drawing review, to write the process flow of parts, we must first know the various technical requirements of parts drawings; Then drawing review is the most important link in the preparation of part process flow.
1. Check whether the drawings are complete.
2. The relationship between drawings and views, whether the labeling is clear and complete, and the size unit.
3. Assembly relationship, assembly requires key dimensions.
4. The difference between the old and new layout.
5. Translation of foreign maps.
6. Table code conversion.
7. Feedback and burying of drawing problems.
8. Materials
9. Quality requirements and process requirements
10. The officially released drawings must be stamped with the seal of quality control.
Three. Matters needing attention in development. The development drawing is a plan (2D) developed according to the part drawing (3D).
1. The expansion mode should be combined, and it is convenient to save materials and processability.
2. Reasonable selection of clearance and edging mode, with clearance of 0.2 below T=2.0 and clearance of 0.5 below T=2-3. The wrapping method adopts long side and short side (door panel).
3. Reasonable consideration of tolerance size: negative difference to the end, positive difference to half; Hole size: positive difference to the end, negative difference to half.
4. Burr direction
5. Tooth extraction, riveting, tearing, punching bumps (bags), etc. , and draw a sectional view.
6. Check the material, thickness and thickness tolerance.
7. For special angles, the inner radius of the bending angle (generally R=0.5) should be enlarged according to the trial bending.
8. Errors (similar asymmetry) should be emphasized.
9. Enlarge the picture where there are many sizes.
10. The places that need spray protection shall be marked.
Four, sheet metal processing technology, according to the differences in the structure of sheet metal parts, the technology can be different, but the total does not exceed the following points. 1, blanking: there are many blanking methods, mainly in the following ways.
(1) Shearer: It is a simple material that is sheared by shears. Mainly for die blanking. The cost is low, and the accuracy is lower than 0.2, but only strips or blocks without holes and corners can be processed.
(2) Punch machine: The flat parts after the parts are unfolded are punched into various shapes on the plate by a punch machine in one or more steps. Its advantages are short working hours, high efficiency, high precision and low cost, and it is suitable for mass production, but it needs to design dies.
(3) CNC blanking. When NC blanking, the NC machining program should be compiled first. Using programming software, the developed drawings should be compiled into recognizable programs of CNC drawing machine tools, so that they can punch out various shapes of flat parts on the flat plate step by step according to these programs. But its structure is influenced by the tool structure, and its cost is low, and its accuracy is 0. 15.
(4) Laser blanking, that is, cutting the structural shape of a flat plate on a large flat plate by laser cutting. Like NC blanking, it is necessary to write a laser program, which can blank various complex shapes of flat plates with high cost and accuracy of 0. 1.
⑤. Sawing machine: mainly uses lower aluminum profiles, square tubes, drawn tubes, round bars, etc., with low cost and low precision.
1. fitter: the angle of counterbore, tapping, reaming and drilling is generally 120℃, which is used for pulling rivets, and the countersunk screws and tapping bottom holes are 90℃.
2. Flanging: also known as hole drawing and hole turning, it is to pull a slightly larger hole from a smaller bottom hole and then tap it. It is mainly processed with thin metal sheet to increase strength and number of thread turns and avoid slipping teeth. It is generally used for shallow flanging with thin thickness and normal hole circumference, and the thickness is basically unchanged. When the thickness is allowed to be reduced by 30-40%, the flanging height can be higher than normal.
3. Stamping: This is a processing procedure formed by a die. Stamping processing generally includes punching, corner cutting, blanking, punching convex hull (bump), punching and tearing, punching and forming. Its processing needs corresponding dies to complete the operation, such as punching blanking die, convex die, tearing die, punching die, forming die and so on. , the operation mainly pays attention to the position and directionality.
4. Riveting: As far as our company is concerned, there are mainly riveting nuts, screws, etc., which are completed by hydraulic riveting machine or punching machine and riveted to sheet metal parts. There are also riveting methods, so we should pay attention to directionality.
5. bending; Bending is to fold a 2D plane part into a D part. Its processing needs folding machine and corresponding bending die to complete, and there is also a certain bending sequence. Its principle is that the next knife folds first without interference, and folds after interference. L the number of bent strips is 6 times of the calculated slot width of the plate thickness below T=3.0mm, such as T= 1.0, V=6 .0 F= 1.8, T= 1.2, V=8, F=2.2 and t =/kloc-. There are cracks in the bending of aluminum plate with straight knife and machete (80℃, 30℃), which can increase the width of the groove of the lower die. Matters needing attention when bending the upper die R (annealing can avoid cracks) L: I drawing, which requires the thickness and quantity of the plate; Ⅱ bending direction Ⅲ bending angle; Ⅳ bending size; ⅵ Appearance and chrome-plated materials are not allowed to wrinkle. Generally speaking, the relationship between bending and riveting process is riveting before bending, but some parts will interfere after riveting, so they must be folded before pressing, and some processes such as bending, riveting and bending are needed.
6. Welding: Definition of welding: The distance between atoms and molecules of the material to be welded is integrated with the crystal lattice of Jingda.
① Classification: A fusion welding: argon arc welding, CO2 welding, gas welding and manual welding; B. pressure welding: spot welding, butt welding and collision welding; Brazing: electrolytic chromium welding and copper wire.
(2) Welding mode: The choice of welding mode for D robot welding, such as AC02 gas shielded welding, B argon arc welding and C spot welding, depends on the actual requirements and materials. Generally speaking, CO2 gas shielded welding is used for iron plate welding; Argon arc welding is used to weld stainless steel and aluminum plate. Robot welding can save working hours, improve working efficiency and welding quality, and reduce working intensity.
③ Welding symbols: Δ fillet welding, д-shaped welding, I-shaped welding, V-shaped welding, single-sided V-shaped welding, blunt-edged V-shaped welding, spot welding (O), plug welding or groove welding (∏), edge welding (χ), blunt-edged single-sided V-shaped welding (V) and blunt-edged U-shaped welding.
④ Arrow line and connector
⑤ Welding defects and preventive measures: spot welding: insufficient strength will bump and impose the welding area; CO2 welding: high productivity, low energy consumption, low cost and strong anti-rust ability; Argon arc welding: deep dissolution, slow melting speed, low efficiency, high production cost and defects of tungsten inclusion, but it has the advantage of good welding quality, and can weld non-ferrous metals such as aluminum, copper and magnesium.
⑥ Causes of welding deformation: insufficient preparation before welding, need to increase fixture, poor welding fixture and poor welding sequence.
⑦ Welding deformation correction methods: flame correction method, vibration method, hammering method and artificial aging method.