Discussion on the hottest double mold curing press

2022-08-24
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Discussion on dual-mode curing press

the first common application of dual-mode curing press is the mechanical curing press, which adopts the crank gear connecting rod (or four connecting rod) structure, and the mechanism principle is simple. The clamping force is added at the moment of clamping, and a larger clamping force can be obtained with a smaller motor power. After clamping, the motor will no longer work, and the clamping force can always be maintained until the mold is reopened. At present, although the mechanical vulcanizers used in the world have different manufacturers, different specifications and models, and have been continuously improved for many years, their basic structures are the same and have not changed

at the same time of the popularization and application of mechanical vulcanization, hydraulic vulcanizers also appeared. However, at the beginning, the superiority of hydraulic curing press over mechanical curing press was not obvious, and the hydraulic technology was not very mature at that time, and the tire factory did not adapt to the maintenance of hydraulic curing press, so hydraulic curing press was not widely promoted as mechanical curing press for a period of time. However, with the continuous development of automobile industry and tire industry, higher and higher requirements are put forward for the uniformity of tires and the working accuracy of vulcanizers. The advantages of hydraulic vulcanizers are fully displayed. At the same time, hydraulic technology is becoming more and more mature, and maintenance is no longer a big problem. So now the major tire companies in the world have gradually adopted hydraulic vulcanizers to replace the traditional mechanical vulcanizers. They have basically adopted hydraulic vulcanizers when building new plants or carrying out technical transformation of old plants. Hydraulic curing press has become an indisputable development trend to replace mechanical curing press

mechanical curing press has its structural characteristics, but this structure also brings some inherent weaknesses

the clamping force of the mechanical curing press is obtained by the elastic deformation of the stressed components. When clamping and applying clamping force, the two ends of the upper beam deflect downward, the two ends of the base deflect upward, the connecting rod is lengthened and its two ends deflect outward, and the lower end of the crank gear and connecting rod deflect outward, as shown in Figure 1. Therefore, even if the new curing press has good manufacturing quality and no wear, these deflections must occur during mold closing. The axis of the vulcanization station will deviate from the theoretical vertical position and be twisted, and this axis will repeat every time the mold is opened and closed from the theoretical vertical position to the twisted position. In other words, the axis has angular rotation at the moment of opening and closing the mold

due to the bending deformation of the stressed member, the clamping force on the mold is not evenly distributed along the circumference, and the force on the outside is greater than that in the middle, as shown in Figure 2. Some vulcanizing machine manufacturers have taken some remedial measures against this problem, such as making the lower end of the crank gear incline inward in advance (the crank gear shaft inclines outward and downward by a small angle) when the mold is not closed, and using wedge-shaped fillers on the upper beam, which plays a certain compensation role for the tires of a specific specification when the vulcanizing machine is not worn, but this compensation role is greatly reduced when the tire specification is changed or the parts of the vulcanizing machine are worn

the dual-mode vulcanization manufacturing process produces a structure equivalent to that produced by the FFF method. The structure of the machine is left-right symmetrical, but due to manufacturing errors, it is impossible to achieve absolute symmetry. Vulcanizing machine manufacturers take various measures to ensure the symmetry of parts, such as connecting rods are processed in pairs, wallboards are processed in pairs, and numerical control machine tools are used as much as possible. However, it is difficult to achieve absolute symmetry for the design seat, crank gear, transmission shaft and transmission gear of the upper beam, bottom body and dynamometer. Due to the problem of symmetry error, in order to ensure the flexible operation of the machine, loose fitting tolerance is generally adopted for the fitting of all moving parts. For example, the fit between connecting rod hole and upper beam shaft and crank pin is (e8/e8), the fit between crank gear shaft and base hole is (e8/e8), the fit between upper beam shaft and roller is (f8/e8), the fit between roller and wallboard guide groove is (h9/f8), and the cumulative gap between upper beam end face, base end face and connecting rod plane is 1.15 ~ 1.5mm. This asymmetry and the existence of these tolerances further adversely affect the clamping accuracy of the vulcanizer, especially the repetition accuracy. The structure of the mechanical vulcanizer also determines that the force exerted by the pin shaft of the upper crossbeam on the upper copper sleeve of the connecting rod, the force exerted by the crank gear shaft on the lower copper sleeve of the connecting rod, and the force exerted by the crank pin on the lower copper sleeve of the connecting rod are uneven, as shown in Figure 1. Moreover, these connecting parts rotate under heavy load, which inevitably leads to uneven wear of these copper sleeves and more serious problems. The wear of the copper sleeve will further reduce the clamping accuracy of the vulcanizer. In order to maintain a certain clamping accuracy of the vulcanizer, the wear degree of these copper sleeves must be checked frequently and replaced in time

in addition, the clamping force of the mechanical vulcanizer is determined by the elastic deformation of each stressed member at the moment when the crank pin reaches the bottom dead center. The change of temperature will change the size of the stressed component, and the clamping force will also change. Therefore, the clamping force of mechanical curing press is sensitive to temperature. Be sure to preheat before putting into use or restart after a period of shutdown. The fluctuation of ambient temperature or working temperature in the production process will cause the fluctuation of clamping force

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