The drying box of the gravure printing machine has a large volume and a complicated structure. In addition, it uses a thin plate material with a thickness of 1 to 6 mm. It is prone to various deformation problems during the manufacturing process, so it has become more difficult to manufacture in all riveted and welded parts 1. One of the parts with high technical content.
1. Deformation problems and preventive measures during the cutting process
In order to prevent the drying box from deforming during the blanking process, the diagonal dimensions of the blanking should be detected while the blanking is being carried out, and the dimensional tolerances of the materials should be strictly controlled. For example, the inner plate of the inner tank of the movable box is generally made of stainless steel, and the expansion coefficient of the stainless steel material is 1.5 times that of the ordinary steel plate, and the thermal conductivity is poor, and its thickness is usually between 1.5 and 2 mm, which belongs to the category of thin plates, so it is used. When the CNC plasma cutting machine cuts, the inner panel will inevitably appear wave deformation.
First, the oxide film and burrs around each cut plate must be removed, and then placed on the platform, tapping with a slat or using a wooden hammer to spread the hammer along the edge of the wave deformation to release the stress, so that the wave deformation can be achieved Flatten out.
2. Deformation problems of ventilation pipes and preventive measures
The bending angle of the ventilation pipe should generally be designed from 330 ° to 345 °, and the requirements for the materials are: flat, straight and accurate. The bending angle is realized by the bending function of the bending machine. In the bending process, a suitable mold must be selected. In view of the inherent resilience of the material itself, the angle during bending should generally exceed the predetermined bending angle by 8 ° to 10 °.
In addition, it is necessary to ensure the consistency of the angle of the air duct nozzle panel and the drying box panel after molding. For this reason, the anti-deformation method can be adopted when assembling the inner liner of the drying box, that is, firstly maintaining a certain angle between the panel of the air duct nozzle and the panel of the drying box, so that after molding, a certain arc will be recessed at the junction The distance between the depth of the depression and the horizontal plane is 2 ~ 3mm, which can be automatically leveled after the welding is completed.
3. Deformation problems and preventive measures in the manufacturing process of the outer plate of the drying box
Generally, the thickness of the outer plate of the drying box is 6mm, which belongs to the category of medium and thick plates. After the blanking is completed, first use an angle grinder or slag hammer to remove burrs and splashes around the plate. If the deformation area of ​​the outer plate is not large, use a hand hammer to strike and disperse the leveling; if the deformation area is large, you can use the three-roller plate machine to place the outer plate on the liner above the roller plate. Just reverse scroll.
4. Deformation problem of inner liner and preventive measures
During the assembly process of the inner liner of the drying box, the air nozzles at the connection between the air ducts on both sides and the middle ventilation pipe will be convexly deformed. In order to avoid this deformation problem, a symmetrical manufacturing method can be adopted when assembling the inner liner, that is, first positioning and welding the air ducts on both sides, and then connecting the middle ventilation pipe; when welding, the middle side plate and the ventilation are first welded inside the air cavity The tube, and then the method of closing the back wall is changed to the method of integrally welding the inner liner after the assembly is completed, and the form of the welding seam is changed to a piecewise symmetrical welding method.
The liner air cavity is one of the core components of the drying box. It is mainly composed of the air duct, the ventilation pipe between the air ducts, the front and rear panels, the upper and lower sealing plates, the air inlet, the arc plate, the air distribution plate, the rear wall, etc. composition. In the assembly process of the inner cavity air cavity, the ventilation tube between the front and rear panels and the air duct should be connected to the inner cavity and the outer panel first, and then the front panel of the air cavity is used as a reference to assemble it by flip-chip To ensure that the four corners of the front panel are always in contact with the platform surface, and then assemble the inner panel, the upper and lower sealing panels and the back wall panel. After the assembly is completed, the alternate seam is hammered with a hand hammer to release the stress generated during welding. It is worth noting that after welding, the two ends of the liner should be fixed and then welded in all positions.
5. Deformation problems and preventive measures of the outer plate of the fixed box of the drying box
There are many holes on the outer plate of the fixed box of the drying box for installing the guide rollers, and the width of the plate surface is narrow (generally 150mm), so the parts with holes on the outer plate of the fixed box are prone to deflection. Based on years of experience, the author believes that the deformation of the fixed box is slightly different due to the total height of the box. According to incomplete statistics: after the assembly of the fixed box with a total height of 1.4m is completed, its deformation is approximately 2.5-3mm After the assembly of the fixed box with a total height of 1.6m is completed, the deformation amount is approximately 3 to 4mm; after the assembly of the fixed box with a total height of 2.4m is completed, the deformation amount is approximately 5 to 7mm. In order to avoid the above-mentioned deformation problems as much as possible, the reverse deformation method can be adopted when assembling the outer plate and the surrounding plate of the fixed box, that is, before welding, the upper and lower edges of the outer plate are hammered with a hand hammer to cause a certain pre-reverse deformation, The amount of pre-reverse deformation is adjusted according to the total height of the fixed box, which is generally about 2% of the total height. After the welding is completed, the internal stress generated by the welding deformation will deform the outer plate, which will cancel out the pre-reverse deformation in advance, so as to achieve the purpose of correcting the deformation of the outer plate of the fixed box.
6. Deformation problems and preventive measures of the peripheral board
Under normal circumstances, the width of the outer plate of the drying box is 1000 ~ 2500mm, and the thickness of the plate is generally 3mm. Because the peripheral board and the outer board have large differences in width and thickness, when welding the two together, the area of ​​the welding heat affected zone is often different due to the difference in welding speed and method, resulting in welding stress Unevenness, which in turn causes uneven wave deformation of the peripheral board.
In order to prevent the occurrence of the above-mentioned deformation problems, the peripheral board should be placed on the platform before welding, and hammered along the outer edge of the peripheral board with a hand hammer to make the plate at this part extend to 1 to 1.5 mm in the fiber direction. After the welding of the peripheral board and the outer board is completed, the pre-deformed peripheral board is restored to its original state due to heat shrinkage, which can alleviate the wave deformation of the peripheral board during the welding process.
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