What is the working process of sheet metal processing ?

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Sheet metal process is the process of separating, deforming, and assembling metal plates, profiles, and pipes in cold and hot states, and manufacturing metal components by welding, riveting, and bolting.

From the perspective of its processing methods, most of them are stamping processing of separation and forming of raw materials under the condition of basically not changing the cross-sectional characteristics of metal sheets, profiles and pipes; from the perspective of its processing technology.

It mainly involves fitter , Stamping, metal cutting, welding, heat treatment, surface treatment, riveting, assembly and other professional types of work or processing technology.

Characteristics and work content of sheet metal process

Features of sheet metal process

Because sheet metal parts mainly use stamping processing technology, and stamping processing which the pressure provided by the stamping equipment, through the stamping die. Then the metal sheet plastic deformed, and the required processing method of parts with a certain shape and size will produce

Sheet metal process has the following features

• It can process parts with complex shapes and produce less waste during the production process.
• The product has sufficient shape and dimensional accuracy, good interchangeability, and good surface quality.
• It is possible to obtain parts with light weight, less material consumption, higher strength and rigidity.
• Machining mostly relies on special molds, and mold manufacturing which complicated and costly. Therefore, only under mass production conditions can reduce the cost of parts produced .

And because the assembly and connection of sheet metal parts mainly use welding processing technology, and welding processing uses heat or pressure, or a combination of both, and with or without filling materials, etc., through the use of the bond between the atoms of two objects. The processing method of water-lasting connection.

Therefore, below is the sheet metal process other features

• Compared with the production and processing of forgings and castings, sheet metal components have the advantages of light weight, energy saving of metal materials, simple processing technology, reduction of production costs, and production costs.
• Most of the metal components that have been welded have low processing accuracy and large welding deformation. Therefore, the post-welding deformation and correction amount are large.
• Since the welded parts are non-detachable and difficult to repair, it is necessary to adopt reasonable assembly methods and assembly procedures to reduce or avoid waste products. On-site assembly of large or extra-large products is often required, so trial assembly should be carried out in the factory first. , It is advisable to use detachable connection and non-detachable connection for temporary replacement lanes during trial installation.
• During the assembly process, it is often necessary to select, adjust, and repeatedly measure and inspect to ensure product quality.

Cold-worked sheet metal process is the processing of blanking, cutting, forming, joining and other processes around raw materials such as plates, profiles, and pipes. It has its own processing characteristics and characteristics, and therefore, has formed its own unique processing content. And production process and operating specifications.

Work content of sheet metal process

Understand sheet metal parts

Understanding the part drawing is the prerequisite for sheet metal process. Only by understanding the part drawing ,we can further analyze the structure of the part, understand the shape, component, size and relevant technical requirements of the component, so as to carry out the subsequent process.

Sheet metal parts drawing is not only the basis for processing, but also the basis for product inspection, and it is an important technical document in production

Unfold and lofting

On the basis of understanding the sheet metal parts drawing, according to the material type, structural characteristics, shape and size requirements of the sheet metal components, based on the analysis and selection of the manufacturing process,

The processed components should be processed appropriately (such as adding After adding the machining allowance, determining the bending radius of the neutral layer of the bending member, etc.), perform the necessary calculations (for the parts that are too complex to be calculated.

It can also be determined through experiments in production) and unfold, so as to obtain the required use in the product manufacturing process. 1:1 scale accurately drawn parts of all or part of the unfolded drawing (the unfolded drawing is the lofted drawing), unfolded data, marking or inspection template, etc.

The open sample is the first process of sheet metal processing. In essence, it is also one of the work contents of formulating process regulations (process documents that specify the manufacturing process and operating methods of sheet metal components).

The preparation of process regulations belongs to the production technology preparation of sheet metal components, and is generally completed by engineering and technical personnel.

However, in different industries and enterprises of different sizes, the preparation of process regulations may be slightly different according to the complexity of the components, or There are situations where cold-worked sheet metal technicians and senior cold-worked sheet metal workers are responsible for the completion.

Normally, ordinary cold-worked sheet metal workers usually only need to complete the drawing (numbering) of the processed components according to the relevant technical documents such as the relevant exhibition drawings and other technical documents, and be responsible for the production of sample rods, templates and other tasks.

Production and processing

According to relevant sheet metal processing technical documents, using various sheet metal processing equipment and tools, and using various processing methods (including heat treatment, surface treatment, etc.), products that meet the requirements of sheet metal parts drawings are manufactured.

Generally, the basic procedures of sheet metal processing include straightening, lofting, blanking, cutting, forming, connection assembly (including welding, riveting, snapping and threading, etc.). According to the nature of the process, it can be divided into four parts: material preparation, lofting, processing and forming, and assembly and connection. The most used cutting and forming processing methods are stamping processing.

Stamping processing can be divided into two major types: separation process and deformation process according to the different deformation properties in the processing process.

Separation process is a stamping processing method that separates the stamping part and the sheet material along the required contour line and obtains a certain section quality;

The deformation process is a stamping processing method that plastically deforms the stamping blank without causing damage to obtain the required shape, size and accuracy.

Separation process

• Blanking: Use the mold to punch the sheet along the closed contour line, and the cut part is the workpiece.

• Punching: Use the mold to punch the sheet along the closed contour line, and the cut part is waste.

• Cut off: Use scissors or a mold to separate the sheet material along the unclosed contour line.

• Incision: Use the mold to cut part of the sheet along the unclosed contour and make it bend down.

• Trimming: Use a mold to punch out the excess material on the edge of the workpiece.

• Sectioned: Use a mold to cut the stamped semi-finished product into two or more workpieces.

Deformation process

It mainly includes bending, deep drawing, forming (flanging, necking, bulging, undulating forming, shaping) cold extrusion and other processes. The main characteristics of each process are as follows.

• Bend: Use the mold to bend the sheet into various angles and shapes.

• Deep drawing: Use a mold to punch the blanks into hollow parts with various openings.

• Ups and downs: Use a mold to locally deepen the sheet into convex and concave shapes.
• Flanging: Use a mold to turn the hole or the outer edge of the sheet into a straight wall.
• Neck: Use the mold to reduce the radial size of the hollow part or the tubular blank.
• Bulging: Use a mold to expand the hollow part or tubular blank to increase the radial dimension.

• Plastic surgery: Flatten the warped flat part or press the inaccurate part of the formed part into the correct shape.
• Cold extrusion: The metal flows along the gap between the convex and concave molds or the cavity of the concave mold, so that the original blank is transformed into a thin-walled hollow part or a semi-finished product

Among them, the most commonly used stamping processes for sheet metal processing are: punching, blanking, notching, cutting, trimming and other separation processes and bending, drawing, flanging and other forming processes.

Follow-up painting and inspection

In order to improve the anti-corrosion, wear resistance, decoration and other functions of the surface of the components, the finished components often need to be painted (mainly electroplating, spray painting, etc.); and in order to ensure the quality of the components and the quality of the finished products. Implement a strict inspection system (including: self-inspection by the processor itself and special inspection by full-time inspectors).

Process flow and process regulations of metal working

Cold-worked metal working is the processing of blanking, cutting, forming, joining and other processes around raw materials such as plates, profiles, and pipes. It has its own processing features and characteristics, so it has formed a unique process and operation specification.

Process flow of sheet metal working

The process flow of sheet metal working refers to the whole process of gradually changing the shape, size, material properties, or assembly and welding of parts in a certain order during the production process, until the sheet metal parts that meet the shape and size requirements are manufactured.

For a more complex structural part, its production and processing generally need to be completed through many processes such as material preparation, unfolding, cutting blanks, forming and assembling, and because cold-worked sheet metal processing is often associated with welding, metal cutting, heat treatment and inspection And other processes are combined to form a complete product manufacturing process. Therefore, its processing flow often includes the above-mentioned processing procedures.

The technological process is an important technical document that guides the entire component process, organization and management of production and processing. For parts processing that are not completed in a workshop or even a factory. It is an important basis for the flow of procedures in each workshop, the division of labor between plants, and the coordination and cooperation with each other.

Because the process flow is the entire route prescribed by each component in the component from the raw material to the completion of the entire component, it is also called the process route.

Process regulations for sheet metal processing

The process flow stipulates the processing flow of the parts, and the specific processing content is guided and controlled by the process regulations.

The process specification is based on the requirements of the product drawings, the characteristics of the workpiece, the production batch, and the company’s existing equipment and production capacity, etc., after a thorough comprehensive analysis and comparison of several possible process plans drawn up by the process technicians, the selection is made.

It is a technical document that guides the production process of a part that is technically feasible and economically reasonable. In the technical document, the blank used for the part, its processing method, and the specific processing size; the nature, quantity, sequence and quality requirements of each process; the model and specifications of the equipment used in each process; the processing used in each process The form of tools (such as auxiliary tools, knives, molds, etc.); the quality requirements and inspection methods and requirements of each process.

The process rules are displayed differently in specific applications. Generally speaking, for a large and complex sheet metal structure, sheet metal workers often need to be completed with the cooperation of electric welders, cranes and other professional work types, while sheet metal parts are directly processed by pressure processing (such as presses, hydraulic presses, etc.) , Is often referred to as stamping process; for the processing technology that uses welding to assemble components, it is often referred to as welding process, and for assembly processing that requires both mechanical processing and welding, riveting and other processing techniques, it is directly called For the assembly process.

Among them: the more commonly used form is the process card. The specific format is different for different companies, but the content included is roughly the same. It mainly includes the name and model of the product, the name of the part, the brand, specification, number of materials, the sequence number, name and content of the process, and the process equipment used to complete each process.

The part shown in the figure below is the boiler front tube plate on a company’s product

The following table shows the process card of this part

The reason why code management is implemented for molds and measuring counties (inspection tools, prototypes) in the process card is to facilitate the production of molds and measuring tools and technical management needs.

Generally speaking, specific to the processing technology of all sheet metal parts, it is often not completed by a blanking and stamping workshop. Many parts may also be interspersed with machining, heat treatment, surface treatment, etc., cross-shop and cross-departmental operation guidance.

It is made by the content of its corresponding process regulations, but in different industries, especially when processing sheet metal components with low professional technical requirements and low complexity, it is often possible to prepare a comprehensive process specification to guide production.

Unfolding of sheet metal components

In the processing of sheet metal parts, workpieces of various shapes are often encountered, such as ventilation pipes, deformed joints, etc., to complete the processing, the sheet metal must first be unfolded.

That is, the surface of the object is according to its actual shape and size , Spread on a flat surface. Sheet metal unfolding is a preparation process for sheet metal blanking, and it is also a prerequisite to ensure the correct processing of sheet metal parts.

Judgement of developable and non-developable surfaces

In production and processing, the shape of sheet metal components is complex and diverse. Despite this, most of them are composed of basic geometric bodies and their combinations. Among them: the basic geometry can be divided into two kinds of plane three-dimensional and curved three-dimensional. Common planar solids (mainly quadrangular prisms, truncated columns, oblique parallel faces, quadrangular pyramids, etc.) and their planar combinations are shown in Figure 2-1 (a). Common curved solids (mainly cylinders, spheres, etc.) , Right cone, oblique cone, etc.) and its curved surface combination as shown in Figure 2-1(b).

From the basic curved three-dimensional sheet metal component shown in Figure 2-1 (b), it can be seen that there is a rotating body formed by a generatrix (primary line-straight line or curve) rotating around a fixed axis. The surface on the outside of the rotating body is called the rotating surface. Cylinders, balls, right cones, etc. are all rotating bodies, and their surfaces are all rotating surfaces, while oblique cones and irregular curved bodies are not rotating bodies. Obviously, a cylinder is formed by rotating a straight line (generator bar) around another straight line and keeping it parallel and equidistant. A right cone is a straight line (generating line) that intersects the axis at one point, and it is formed by rotating at a certain angle. The generatrix of the sphere is a semicircular arc, which is formed by rotating the diameter as the axis.

The surface of the body can be divided into two types: expandable surface and non-expandable surface. To judge whether a curved surface or part of a curved surface is stretchable, you can use a ruler to lean against the object and rotate the ruler to see if the ruler can be fully aligned with the surface of the object in a certain direction.

If it can fit, write down this Position, and then select a new close position at any point nearby.If the line of the ruler after close is parallel to each other, or all intersect at one point (or extend and intersect at one point), then the object is measured The surface of the part is stretchable. In other words, when two adjacent straight lines (primary lines) on the surface can form a plane (that is, two straight lines are parallel or intersect), they can be expanded. These types of surfaces include plane solids, cylinders, cones, etc.; any surface where the generatrix is a curve or two adjacent prime lines are intersecting lines are non-developable surfaces, such as spheres, rings, spirals, and other non-expandable surfaces. Regular curved surfaces, etc. For non-developable surfaces, only approximate expansion can be done.

The bending machine is an important machine required in the sheet metal processing process. Due to the electromagnetic clamping, the bending machine can meet the requirements of processing a variety of workpieces, and it can process workpieces with side walls, and the operation is also very good and simple.

• Turn on the power, turn on the switch on the control panel, and then start the oil pump, so you can hear the sound of the oil pump rotating. (The machine does not operate at this time)
• Stroke adjustment, you must pay attention to adjusting the stroke when using it, and you must test it before bending. There must be a gap of plate thickness when its upper die descends to the bottom. Otherwise it will cause damage to the mold machine. The adjustment of the stroke also has electric quick adjustment.
• For the selection of bending notches, a notch with a width of 8 times the thickness of the plate should generally be selected. If you bend a 4 mm sheet, you need to choose a slot of about 32.
• Backgauge adjustment generally has electric quick adjustment and manual fine adjustment, the method is the same as the shearing machine.
• Step on the foot switch to start bending. The CNC bending machine mold is different from the shearing machine. It can be released at any time, and the foot will stop when you release it, and it will continue to go down when you step on it.

Matters needing attention when operating and controlling the bending machine

• Before work, carefully inspect whether all parts of the bending machine are normal, whether the electrical equipment is intact, whether the lubrication system (including: circulating lubrication system, centralized lubrication system, etc.) is unblocked; clear the table and its surroundings such as tools, measuring tools and other debris and edges Corner scrap.
• Do not operate and control the bending machine by one person alone. Two or three people should coordinate the feeding, control dimensional accuracy (precision) and reclaiming, etc., and make sure that one person is responsible for the unified command.
• Adjust the scissors gap of the bending machine according to the specified shearing thickness. When the hydraulic bending machine is in use, the wire is energized to the coil, and after the power is energized, a gravitational force is generated on the pressure plate, thereby realizing the clamping of the thin plate between the pressure plate and the base. Due to the use of electromagnetic force clamping, the pressing plate can be made into a variety of workpiece requirements, and workpieces with side walls can be processed. It is not allowed to cut two kinds of sheets of different specifications and different material qualities at the same time; do not cut by overlapping materials. The cut sheet requires a flat surface, and it is not allowed to cut narrow sheets that cannot be compressed.
• The fingers of the bending machine operating controller should keep a distance of less than 200mm from the scissors mouth, and leave the pressing device. The protective fence installed on the bending machine cannot block the eyes of the operator and cannot see the cut part. The waste generated after the operation has edges and corners, and the operator should remove it in time to prevent stab wounds and cuts.