With the development of various situations at home and abroad, as well as the increasingly fierce market competition, the products are continuously upgraded. In order to meet the individual needs of users, and to quickly undertake the trial production tasks of the design unit. The production technology of some related special vehicles has gradually developed and matured. The following mainly talks about some applications of sheet metal bending technology in the production of special vehicles.
Review elements of bending process
In order to standardize the application of the bending process in production, strict and detailed special vehicle bending design process review standards have been formulated, and the product design is closely cooperated to optimize the parts in the early design stage, such as the r-bending angle Radius, r1—one-time bending angle radius, α—bending angle angle, t—sheet thickness, V—bending opening width, L—bending linear length, W—minimum reserved length for second bending, a —Bending length, b—the length of the middle section of the second bending, T—bending machine tonnage, R—box bending corner radius and other related standards have made relevant regulations, which effectively solves the irrationality of related designs And the change cycle, to the greatest extent to ensure the manufacturability of the product.
Selection of bending tools
The upper die of the 63T2500 DA52S 4+1 Press Brake is mainly divided into three categories: straight knife, machete, and sharp knife.
(1) Taking into account the structure of the product comprehensively, two types of upper molds, scimitar and straight knife are configured. Straight knives are mainly used for small bending parts on the car body, and scimitars are used for bending parts with complex structures and easily interfere with the tool more than twice, which can meet the bending needs of special equipment.
(2) The lower mold adopts a V-shaped groove, and we basically use V=6 times the material thickness to determine the width of the V port. The process should be based on the actual product output and production frequency to arrange the V-ports of the V-shaped grooves in a reasonable manner, so as to minimize the number of mold changes on the same equipment during production, improve production efficiency, and reduce mold replacement costs; such as us Put the most commonly used V=9mm V port on the main working surface of the lower mold. At the same time, you can also place several spare commonly used V ports on the secondary working surface to make reasonable use of the lower mold to maximize the service life of the mold.
Special mold maintenance
The maintenance of the special vehicle bending mold is based on the special needs of the product. The maintenance requirements are higher than those of ordinary products. The maintenance cycle, maintenance items, and replacement cycle must be strictly regulated. Long-term production of bending tools will inevitably produce irreversible Wear and tear, causing quality problems such as the bending opening, angle, straightness and external surface indentation of the workpiece. The actual experience of working face grinding is generally not more than 3 times. Considering the production cost, the preventive maintenance thinking should be adopted in the production. Parts or other factors reduce the consumption of molds to a minimum. The more common requirements we adopt mainly include: tool status check, part process check, pay attention to the quality of part section cutting, and reduce the damage of foreign matter to the tool.
Measures to ensure the dimensions of bending parts
The current common structure of special vehicles is a frame structure plus a skin structure. The car body is mainly composed of laser cutting parts, bending parts, and stamping parts. The subsequent welding methods are also different according to the material and protection needs. Therefore, the frame size must be strictly guaranteed at the initial stage of manufacture, and the diagonal error shall not be greater than 4mm. This also puts forward higher dimensional accuracy requirements for the outer surface of the car body bending parts. The angle, flange size, straightness, and outer surface quality of the corresponding bending parts must also be strictly controlled.
In the process of special material sheet metal bending, due to the special properties of the sheet metal, we often encounter the problem of springback, and plastic deformation and elastic deformation exist at the same time. At the end of bending, springback occurs due to the recovery of elastic deformation.
The springback phenomenon directly affects the dimensional accuracy of the workpiece and must be controlled. The technological measures adopted for this are: angle compensation method, if the bending angle of the workpiece is 90°, the opening angle of the lower groove (V-shaped) of the 80T2500 DA52S 4+1 Press Brake can be 78°, or the angle can be compensated during programming according to actual data; also The pressurization time increase correction method can be used to perform pressurization correction at the end of bending to prolong the contact time of the upper die, workpiece, and lower groove of the bending machine to increase the degree of plastic deformation at the fillet of the lower groove, so that the fiber in the tension and compression zone The rebound trends resist each other, thereby reducing rebound. At the same time, it is recommended to record and verify each round of data during the formulation of any kind of process parameters, which is beneficial to the stability of the later production process and the search for quality problems.
For related bending problems, you can adjust the inner and outer directions of the shearing surface of the sheet. Deburr the workpiece before bending, and use a manual grinder to grind the cracked part after bending. For different workpieces, the process should be refined, the assembly size relationship should be understood, and the bending sequence should be set correctly.
At the same time, in order to ensure the size of the bending parts, the main positioning method we currently use is the edge positioning and positioning hole positioning of the numerical control block. The two positioning methods have their own advantages and disadvantages: side positioning has fast production efficiency and can be pushed continuously, but side positioning depends on the accuracy of cutting or blanking. Once the sheet has beveled edges or other poor cutting, it will directly affect To the bending accuracy; while the hole positioning reduces the dependence on the sheet material, and the positioning holes are artificially added to the parts, but different types of bending molds need to be debugged multiple times, which appears to be in the production of multiple varieties and small batches low efficiency. Therefore, for different bending parts, we must confirm the functions of the corresponding parts of the size in actual production, so as to determine whether it is continuous pushing or turning bending. The corresponding guaranteed accuracy produced by these two bending methods is also different. of. In addition, all special equipment bending parts are inspected according to process requirements.
80T3200 DA52S 4+1 Press Brake is one of the common equipment in modern mold processing. The main working mode of most CNC bending machines is the upper piston press, and its driving force has characteristics, which has a great relationship with the production process of the bending machine mold. However, it is undeniable that the matters needing attention in normal use include the following:
Safety precautions for the operation of CNC bending machine
The working feature of the CNC bending machine is that pressure is formed by two working hydraulic cylinders that move in parallel. This pressure is vertically downward, and the pressure can drive the mold of the bending beam to perform bending work. The typical bending process of the upper bending beam has several stages and links, including downward movement, static state and decompression, return stroke, etc.:
The downward closing movement of the ordinary bending machine is generally a free fall type, that is, the movement is generated by the weight of the bending machine itself; but the production of the CNC bending machine mold is not like this, but a hydraulic cylinder rodless cavity is used. Generate pressure, so the fast forward speed can reach 250mm/s, which is suitable for the production of strong molds.
The movement starts from the top dead center, at the end it can pass a short brake, and ends after the distance of the sheet is bent. The specific adjustment can be made according to the different requirements of the mold manufacturing.
When the bending machine is at the rest position, the upper bending beam is at the upper dead center. This state is to produce uncontrolled downward movement.
The pressure reduction of the rodless cavity or when the bottom dead center is reached, the pressure holding time starts, which can further improve the accuracy of the parts. Both holding and decompression can be controlled by a proportional directional valve. Customize the running time according to your needs. When decompression is needed, it can be shortened as much as possible, but the decompression should not be too steep and be as stable as possible. The return stroke here involves a large return speed, which is mainly dependent on the flow rate of the pump and the pressure area of the rod cavity of the hydraulic cylinder. Under normal circumstances, the closer to the speed, the higher the return efficiency. The backhaul also requires synchronization.
Stamping and bending
One stage is stamping and bending, which is a key link in the production of bending machine molds. It is also a link. The stamping speed is limited by the oil supply of the oil pump and is also subject to manual intervention by the proportional valve directional valve.
The main links of the mold production process of CNC bending machine are probably these five processes. Each process involves several factors, including the quality and parameter indicators of the machine itself, and also includes human intervention, which may affect the bending. Production and production of machine molds.
0086 555 8327689