Views: 133 Author: Site Editor Publish Time: 2018-12-11 Origin: Site
The bending machine is an important equipment for bending and forming the workpiece in the sheet metal industry. Its function is to press the steel plate into various shapes according to the process requirements. Figure 1 shows the structure of the hydraulic sheet metal bending machine. It consists of left and right vertical columns, workbench and beam. The left and right cylinders are fixed on the column. The slider is connected with the piston of the cylinder and along the guide rail fixed on the column. Up and down movement, the lower mold is fixed on the workbench, the upper mold is installed at the lower end of the slider, and the hydraulic system provides power, the electrical system gives instructions that, under the action of the cylinder, the slider drives the upper die to the lower die and the lower die to achieve the bending of the sheet.
Figure 1——Hydraulic sheet bending machine structure diagram
1.Left and right uprights 2.Slider 3. Workbench 4.Left and right cylinders 5.Mold 6.Hydraulic system 7.Electrical system
The left and right columns, workbench and slider (hereinafter referred to as the three major parts) are the key parts of the bending machine. The sum of the weights of the three large parts accounts for 70%~80% of the total weight of a bending machine. Its strength and rigidity directly determine the running accuracy, service life of the machine and the accuracy of the workpiece. The three-piece large-tonnage bending machine often exceeds the size and weight of road and rail transportation. It is relatively easy to transport ultra-wide and heavy-duty parts in the plain area. The transportation cost of ultra-wide and overweight parts in mountain roads or tunnels is very high, and sometimes even Unable to transport. In order to solve this problem, the three-piece width split or height split structure has been developed. The parts that are still over-limit after splitting are layered in the thickness direction, and the strength and rigidity after assembly meet the requirements, which is convenient for transportation and installation. the goal of.
1.1 Column stress analysis
The bending machine column is divided into two parts, which are respectively symmetrical on the left and right sides, and are respectively installed on both sides of the machine tool. During the working process of the machine tool, the reaction force of the bending workpiece is finally transmitted to the column through the table and the slider, which is the main force part of the machine tool. Since the column has a C-shaped structure, as shown in Fig. 2, a pair of balanced internal forces opposite to the bending force F are generated upward and downward at the throat portion of the column, and the throat is deformed. The throat depth C is larger, and the throat opening angle is increased. The larger the α, the deformation of the throat affects the center line when the upper and lower molds are closed, which causes the precision of the workpiece to deteriorate. Since the force of the column is the fatigue deformation process, the column will be permanently deformed as the working time increases. In order to meet the strength, the width B of the column throat should be continuously widened. For the high-precision bending machine, the rigidity requirement must be satisfied, and the throat width B should be further widened. As a result, the total width H of the column increases, and some exceed the delivery limit.
Figure 2——Throat deformation diagram
α-throat opening angle C-throat depth B-column throat width H-column total width F-bending force
1.2 Slider and table force analysis
The slider is mounted on the lower end surface of the plunger or piston rod of the cylinder, and the table is mounted on the support surface of the lower end of the left and right columns. Both of them are the key parts directly involved in the bending of the workpiece. The rigidity of the table and the slider directly affects the forming of the workpiece. After the angle and straightness accuracy, both the slider and the table are the forces of the simply supported beam, and the direction of the force is opposite, so only the force of the slider is analyzed. As shown in Figure 3, the slider is forced to take the cylinder rod or plunger connection surface as the fulcrum, and the middle is subjected to uniform load according to the length of the workpiece. For the slider of the same tonnage bending machine, the deformation amount f is related to the cylinder center distance L, the slider height H, the length of the workpiece, etc.
To meet the strength or stiffness requirements, the larger the center distance L of the two cylinders or the full load bending workpiece. The shorter the length, the higher the slider height H is required and may exceed the shipping limit.
Figure 3——Schematic diagram of the force deformation of the slider
f-slider maximum deflection deformation H-slider height L-two cylinder center distance F-bending force
2.1 Pseudo-column structure
The bending machine column has different values according to different tonnages and different throat depths. The larger the tonnage, the wider the column. The deeper the throat of the same tonnage machine, the wider the column. Separate or layered treatment is required when the column exceeds the transport limit requirements to ensure that the weight and dimensions of each piece are within transport limits.
Figure 4——Schematic diagram of the front and rear split structure of the column
1.Front of the column 2.Rear of the column 3.Plywood 4.Pin 5.Flange screw
As shown in Figure 4, the 2500t column has a depth of 1600mm. The total width of the column is divided into two parts: the front part of the column H1 and the rear part of the column H2. The upper and lower columns are connected by the clamping plate, and are positioned by the pin shaft, and have a certain interference elimination gap. The middle is connected by flange screws, and the pre-tightening torque ensures that the front and rear bodies become a rigid body. The key is the selection of the parting surface. The parting surface is preferably selected in the section where the column is not elongated and deformed along the height direction. At this time, the connecting parts such as the pin shaft and the screw are only subjected to the tensile force, and the force is reasonable and the connection is reliable. When the parting surface is front or back, the strength of the joint should be higher.
2.2 Separate structure before and after layer thickness stratification
For the super-tonnage bending machine, after the front and rear split, the weight of the front part of the column is still overweight and wide, and it cannot be transported normally. At this time, due to the limitation of the throat depth, it is impossible to carry out the front and rear splits, and it is necessary to layer and combine in thickness. As shown in Figure 5, the 3000t throat has a depth of 1100 mm. The inner and outer parts of the front part of the column are positioned by the pin, the screws are pre-tightened, and then connected to the rear of the column. The screws are pre-tightened so that the three reach a rigid body. The three pieces are individually controlled within transport limits for easy transport and installation.
Figure 5——Schematic diagram of the split structure before and after the thickness of the column
1.The inside of the front part of the column 2.The front side of the column 3.The rear part of the column 4.Vertical positioning key 5.Front and rear flange screws 6.Layered connection screws 7.Layered positioning pins
3.1 Slider split structure
In order to meet the strength and rigidity of the slider, the larger the tonnage of the bending machine, the higher the height of the slider, the longer the slider of the same tonnage bending machine, the higher the height of the slider.
Separate or layered treatment is required when the slider exceeds the transport limit requirements to ensure that the weight and dimensions of each individual piece are within transport limits. As shown in Figure 6, the 3600t slider has a length of 14000mm. The height H of the slider is divided into two parts: the slider lower body H1 and the upper slider body H2. The two ends are positioned and expanded by the clamping plate and the pin shaft, and the flange is pre-tensioned with the flange screw. The connection makes the upper and lower bodies a rigid body. The key is the selection of the upper and lower parting surfaces. The parting surface is selected in the section of the slider body which is not elongated and deformed along the length direction. At this time, the pin shaft and the screw are only subjected to the tensile force, the force is reasonable, and the connection is reliable. When the parting surface is lowered or raised, the strength of the connecting piece should be higher.
Figure 6——Schematic diagram of the upper and lower split structure of the slider
1.Lower slider body 2.Upper slider body 3.Plywood 4.Pin shaft 5.Flange screw
3.2 Slider thickness layered upper and lower split structure
The large tonnage long specification bending machine slider is still overweight after being separated from the upper and lower parts. It needs to be separated and then layered in the thickness direction to achieve the purpose of transportation and installation. As shown in Figure 7, the structure of the 3000t slider is 14200mm. The slider consists of the front part of the lower part of the slider, the rear part of the lower part of the slider and the upper part of the upper part of the slider. The front and rear parts of the lower part of the slider are positioned by the pin. The front and rear flange screws are pre-tightened and connected to the upper part of the slider. The multi-row key is positioned and the flange screws are pre-tightened to achieve a rigid body.
Figure 7——Schematic diagram of the upper and lower split structure of the slider
1.The lower part of the lower part of the slider 2.The rear part of the lower part of the slider 3.The upper part of the slider 4.The pin shaft 5.Front and rear flange screws 6.Positioning keys 7.Upper and lower flange screws
3.3 Workbench split structure
The workbench is divided into two types according to the machine structure. As shown in Fig. 8a, the upper and lower body connection modes are used. The structure is mostly used in the long workbench or the gantry type column, and is composed of the upper body of the workbench and the lower body of the workbench. Both ends of the profile are positioned and expanded by the pinch pin, and the middle is fastened by a locking screw. As shown in Fig. 8b, the front and rear split connection modes are mostly used in the C-type column type, which consists of the table front body and the work table rear body. The semi-circular block connected by the work table and the column is positioned, and the thickness direction is passed. The front and rear connecting screws are pre-tightened. The front and rear split type has no parting surface problem, and the rigidity is better than the upper and lower split type, but the width of the table is limited by the delivery limit.
Figure 8——Schematic diagram of the upper and lower parts of the table
1.Workbench upper body 2.Workbench lower body 3.Plywood 4.Pin shaft 5.Flange screw 6.Workbench front body 7.Workbench rear body 8.Front and rear connection screws
The multi-layer split combination structure of the bending machine column, work table and slider solves various problems that the integral parts of the large-tonnage long-size bending machine cannot be transported and installed. The single-piece main plate of the combined structure is made of medium-thick steel plate, and the material has high strength limit and material cost is reduced. The thickness of the combined structure is increased over the overall thickness, so the strength is increased, the stability is better, and the final formed workpiece is more precise. It has been used for many years on the CNC bending machine above 2500t, and the effect is very good. It can be promoted in the design of large tonnage bending machine.
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