Common sheet metal processing is mainly composed of six steps, which are described in detail below: sheet metal processing drawing design-> laser processing or (numerical control stamping)-> bending-> welding forming-> electrostatic powder spraying or (liquid paint)-> packaging and shipment.
1. Drawing design: general customers provide drawings or samples, which are measured, designed and unfolded by the company’s engineers to form a processing decomposition drawing and an assembly drawing and submit them to the production department for processing.
2, Laser processing: laser cutting machine, can be used for cutting materials such as carbon steel, stainless steel, etc. Using laser cutting, the section of the workpiece after processing is neat, smooth and beautiful, and the size is accurate, which has more advantages for workpieces with arcs, and is an irreplaceable processing method for general CNC stamping.
3. Numerical control stamping: The turret numerical control punching machine mainly aims at products with thin material thickness, which is generally suitable for materials below 2.5mm, and workpieces with many holes in sheet metal processing or requiring special molds to be processed. When the batch is large, using numerical control stamping has certain cost advantages.
4. Bending: If most of the workpieces need to be bent after being laid, the company has several computer bending machines, which are not only fast, but also more accurate in workpiece processing.
5. Welding forming: The workpieces generally need to be assembled and formed after being laid. There are many ways of assembly. Some of them are directly formed by non-welding processes such as screws and riveting. Generally, mechanical shell sheet metal is mostly formed by welding. Companies generally adopt argon arc welding, collision welding, carbon dioxide welding, etc. After welding, the workpieces are polished and polished, so that the workpieces are firm and beautiful.
5. Electrostatic powder spraying: Electrostatic powder spraying is mainly aimed at carbon steel workpieces. Generally, processes such as degreasing and rust removal, surface adjustment and cleaning, phosphating treatment, electrostatic powder spraying, high temperature baking, etc. are carried out first, and the treated workpieces have beautiful surfaces, will not rust for several years, and have the advantages of low cost.
Liquid paint: This process is different from electrostatic powder spraying. Generally speaking, for large workpieces, using liquid paint has the advantages of convenience and low cost when it cannot be transported. Generally, liquid paint is divided into two steps, and the workpiece is treated with primer and then topcoat.
6. Packaging and delivery: 100% inspection shall be conducted before packaging, and inspection data shall be provided. The delivery requirements and packaging method are confirmed by the customer’s representative on site, and are hereby recorded for the customer’s reconfirmation.
Introduction of process technology
1, Sheet metal processing method:
(1) Non-die processing: The process of processing sheet metal by punching, laser cutting, shearing machine, folding machine, riveting machine and other equipment is generally used for sample making or small batch production, with high cost.
(2) Mould processing: Sheet metal is processed by fixed moulds, generally including blanking dies and forming dies, which are mainly used for mass production with low cost.
2, Sheet metal processing technology
Blanking: punching, laser cutting and plate shearing.
Forming-bending, stretching and punching: bending machine, punching machine, etc.
Other processing: riveting, tapping and so on.
Connection mode of sheet metal
Surface treatment: powder spraying, electroplating, wire drawing, screen printing, etc.
1) Sheet metal processing technology-blanking
The blanking methods of sheet metal mainly include punching, laser cutting, shearing machine, die blanking, etc. At present, punching is commonly used, laser cutting is mostly used in proofing stage, and the processing cost is high, while die blanking is mostly used for mass processing.
Below we mainly introduce the blanking of sheet metal with several punches.
Several punching, also called turret punching, can be used for blanking, punching, stretching holes, pressing ribs, etc., and its machining accuracy can reach+/-0.1 mm. The thickness of the plate that can be processed by several punches is as follows:
Cold rolled plate and hot rolled plate ≤ 3.0mm.
Aluminum plate ≤4.0mm
Stainless steel plate ≤2.0mm
(1) Punching requires small size. The small size of punching hole is related to the shape of hole, the mechanical properties of material and the thickness of material. (as shown below)
(2) The hole spacing and hole margin of several punches. The small distance between the punching edge and the shape of the part is limited with the shape of the part and the hole. When the punching edge is not parallel to the shape of the part, the small distance should be not less than the material thickness t; Parallel, should not be less than 1.5t t..
(3) When drawing holes, the small distance between the drawing hole and the edge is 3T, the small distance between two drawing holes is 6T, and the small safe distance between the drawing hole and the bending edge (inside) is 3T+R(T is the thickness of sheet metal, and r is the bending fillet).
(4) When punching a stretch bending part and a deep drawing part, a certain distance should be kept between the hole wall and the straight wall.
2) Sheet metal processing technology-forming
The forming of sheet metal is mainly bending and stretching of sheet metal.
(1) Sheet metal bending
Basic principles of bending processing sequence: bending from inside to outside, bending from small to large, bending the special shape first, then bending the general shape, and the former process will not affect or interfere with the subsequent process after forming.
the small bending radius of bending parts:
When the material is bent, the outer layer is stretched and the inner layer is compressed in the fillet area. When the thickness of the material is constant, the smaller the internal R is, the more serious the tension and compression of the material will be. When the tensile stress of the outer fillet exceeds the ultimate strength of the material, cracks and breaks will occur. Therefore, the structural design of bending parts should avoid too small radius of bending fillet.
Sheet metal drawing
The drawing of sheet metal is mainly completed by several punches or general punches, and various drawing punches or dies are needed. The shape of the drawing parts should be as simple and symmetrical as possible, and the drawing should be formed at one time as much as possible. Parts that need to be stretched many times should allow traces that may be produced on the surface during stretching. On the premise of assembly requirements, the stretching side wall should be allowed to have a certain inclination.
(3) Other forming of sheet metal:
Reinforcing ribs —— Pressing ribs on plate-shaped metal parts helps to increase structural rigidity.
Louvers-Louvers are usually used in various enclosures or casings to ventilate and dissipate heat.
Hole flanging (drawing hole)-used to process threads or improve the rigidity of air interface.
3, Sheet metal processing technology-welding
When designing the welding structure of sheet metal, we should implement the principle of “symmetrically arranging welds and solder joints, and avoid intersection, aggregation and overlap. The minor welds and solder joints can be interrupted, and the main welds and solder joints should be connected. Arc welding and resistance welding are commonly used in sheet metal.
(1) Arc welding
There should be enough welding space between the metal plates, the welding gap should be 0.5-0.8 mm, and the weld should be even and flat.
(2) Resistance welding
The welding surface shall be smooth and free from wrinkles and springback.
4, Sheet metal processing technology-connection mode
This paper mainly introduces the connection methods of sheet metal in the process of machining, mainly including rivet riveting, welding (as mentioned above), punching riveting and TOX riveting.
(1) Rivet riveting: This kind of rivet is often called pulling nail, and it is called pulling riveting when two plates are riveted together by pulling nail.
(2) Punching riveting:
One of the parts is a drawing hole, and the other part is a countersink, which can be made into a non-detachable connector by riveting die. Advantages: the countersink matched with the drawing hole has positioning function, high riveting strength and high riveting efficiency through the die.
Through a simple punch, the connected parts are pressed into the female die. Under further pressure, the materials in the female die “flow” outward. As a result, a round connection point with no edges and corners and no burrs is produced, and its corrosion resistance will not be affected. Even for the plate with coating or paint coating on the surface, the original rust-proof and corrosion-resistant characteristics can be retained, because the coating and paint coating also deform and flow together. The materials are squeezed to both sides and into the plate near the female die, thus forming to.
5, Sheet metal processing technology-surface treatment
The surface treatment of sheet metal can play the role of anti-corrosion protection and decoration. Common surface treatments of sheet metal include powder spraying, electro-galvanizing, hot-dip galvanizing, surface oxidation, surface wire drawing, screen printing, etc.
Oil stain, rust and welding slag on the surface of sheet metal should be removed before surface treatment.
(1) Powder spraying: The surface of sheet metal is sprayed with liquid paint and powder paint, and powder paint is commonly used. By powder spraying, electrostatic adsorption and high-temperature baking, a layer of paint with various colors is sprayed on the surface of sheet metal to beautify the appearance and improve the corrosion resistance of the material. It is a common surface treatment method.
(2) Galvanizing and hot-dip galvanizing: Galvanizing on the surface of sheet metal is a common anti-corrosion treatment method, and it can beautify the appearance to some extent. Galvanizing can be divided into electro-galvanizing and hot-dip galvanizing. The appearance of electro-zinc plating is bright and flat, and the galvanized layer is thin, so it is commonly used. The galvanized layer of hot-dip galvanizing is thicker and can produce zinc-iron alloy layer, and its corrosion resistance is stronger than that of electro-galvanizing.
(3) Surface oxidation: The surface anodizing of aluminum and aluminum alloys is mainly introduced here. The surface anodizing of aluminum and aluminum alloy can be oxidized into various colors, which plays a protective role and has a good decorative role. At the same time, the anodic oxide film can be produced on the surface of the material, which has high hardness and wear resistance, as well as good electrical insulation and heat insulation.
(4) Surface drawing: the material is placed between the upper and lower rollers of the wire drawing machine, and an abrasive belt is attached to the roller. Driven by a motor, the material passes through the upper and lower abrasive belts, and traces are drawn on the surface of the material. According to the different abrasive belts, the thickness of the traces is different, which is mainly used to beautify the appearance. Generally, the surface treatment method of drawing is only considered for aluminum.
(5) Screen printing: the process of screen printing various marks on the surface of materials. Generally, there are two methods: flat screen printing and pad printing. Flat screen printing is mainly used on general planes, but pad printing is needed if there are deep pits. Screen printing requires a screen printing die.