With the development of society, sheet metal industry also develops rapidly. Now sheet metal involves all walks of life. For any sheet metal part, it has a certain processing process, that is, the so-called process flow. To understand the process flow of sheet metal processing, the first thing is to know the selection of sheet metal materials.
Selection of materials.
Sheet metal processing commonly used materials are cold-rolled sheet, hot-rolled sheet, galvanized sheet, brass, copper, beryllium copper, aluminum sheet, aluminum profile, stainless steel and so on. According to the different roles of products, different materials are selected. Generally, products and their uses and costs need to be considered.
1. Cold-rolled sheet: Mainly used for electroplating and paint-baking, low cost, easy to form, material thickness < 3.2mm.
2. Hot-rolled plate: material T (> 3.0mm), is also electroplated, paint parts, low cost, but difficult to form, mainly flat parts.
3. Galvanized sheet SECC, SGCC. SECC electrolytic board is divided into N material, P material and N material, which are mainly not treated by surface treatment and have high cost. P material is used for spraying parts.
4. Copper: Mainly used as conductive material. Its surface treatment is nickel plating, chromium plating, or no treatment, with high cost.
5. Aluminum plate: generally used surface chromate (J11-A), oxidation (conductive oxidation, chemical oxidation), high cost, silver plating, nickel plating.
6. Aluminum Profile: Material with complex cross-section structure, which is widely used in various kinds of boxes, and its surface treatment is the same as that of aluminium plate.
7. Stainless steel: Mainly used for no surface treatment, high cost.
2. In order to compile the technological process of the parts, the first step is to know the various technical requirements of the parts drawings, which is the most important link in the process of the parts.
1. Check whether the drawings are complete.
2. Graphic view relationship, whether the labeling is clear and complete, labeling size units;
3. Assembly relationship, key dimensions of assembly requirements;
4. The difference between old and new layout;
5. Translation of foreign pictures;
6. Code conversion at the table;
7. Feedback and burying of graphic problems;
8. Materials;
9. Quality requirements and process requirements;
10. The quality control stamp shall be affixed to the official drawing.
3. Attentions to unfolding, unfolding drawing is based on part drawing (3D) unfolding plane drawing (2D)
1. The deployment method should be in line with the requirements of material saving and processability.
2. Reasonable selection of question gap and edge-wrapping method, T=2.0 below question gap 0.2, T=2-3 question gap 0.5, edge-wrapping method using long edge wrapping short edge;
3. Rational consideration of tolerance shape size: negative difference goes to the end, positive difference goes half; hole size: positive difference goes to the end, negative difference goes half;
4. Burr direction;
5. Draw sectional views in the direction of teeth extraction, riveting, tearing, punching and convex points (bags).
6. Check material, thickness and tolerance.
7. For a special angle, the radius of the bending angle (R = 0.5) should be expanded according to the bending test.
8. Emphasis should be given to the places where mistakes are prone (similar asymmetry);
9. Enlarged maps should be added in places with larger sizes.
10. The place to be protected by spraying should be indicated.
4. The technological process of sheet metal processing may vary according to the structural differences of sheet metal parts, but generally does not exceed the following points:
1. Cutting: There are various ways of cutting, mainly the following ways
(1) Shearing machine: It is used to cut simple strip parts. It mainly prepares for blanking forming of die. It has low cost and accuracy less than 0.2, but it can only process strip or block without hole and cut angle.
(2) Punch: It is to use the punch to punch the sheet metal parts into various shapes in one or more steps. Its advantages are short time consuming, high efficiency, high precision, low cost, suitable for mass production, but the die should be designed.
NC NC blanking: NC blanking should first write NC processing program, using programming software, the drawing of the expansion diagram is compiled into NC numerical broaching machine tool recognizable program, so that according to these programs one by one, blanking flat parts of various structural shapes on the plate, but its structure is affected by the structure of the tool, low cost, accuracy is less than 0.15.
Laser cutting: Using laser cutting method, the structural shape of the plate is cut out on the large plate. Like NC cutting, it needs to write a laser program. It can cut various complex shaped plate parts with high cost and accuracy of 0.1.
Sawing Machine: Mainly used for aluminum profiles, square pipes, drawing pipes, round bars and so on, low cost, low precision.
2. Flanging: also known as punching and flanging, is to draw a slightly larger hole on a smaller base hole and tap it again. It is mainly used for sheet metal processing with thinner plate thickness to increase its strength and number of thread loops and avoid slippery teeth. It is generally used for shallow flanging with thinner plate thickness and normal hole periphery. The thickness of flanging is basically unchanged. When the thickness of flanging is allowed to become thinner by 30-40%, it can be higher than that of normal flanging. The maximum flanging height can be obtained by extruding 50% at a height of 40-60% higher. When the plate thickness is larger, such as 2.0, 2.5 or more, the plate thickness can be tapped directly.
3. Punching machine: It is the process of forming with die. Generally, punching machine processes punching, corner cutting, blanking, punching convex package, punching tearing, punching, forming and other processing methods. Its processing needs corresponding die to complete the operation, such as punching blanking die, punching blanking die, tearing die, punching die, forming die, etc. The operation mainly pays attention to location and direction.
4. Riveting: For our company, riveting mainly includes riveting nuts, screws, looseness, etc. It is through hydraulic riveting machine or punch to complete the operation, riveting it to sheet metal parts, and riveting method, need to be noted.
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