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Threaded ring work size calculation

by:CSSSLD     2021-01-23
Theoretical analysis and production practice shows that the lack of big size plastic injection processing mold cavity stiffness is the main contradiction, cavity wall thickness and the stiffness conditions shall prevail, for the small size of the mold cavity, in the event of large elastic deformation, the stress is often more than the allowable stress of mold material, so the insufficient strength is the main contradiction, therefore, design of cavity wall thickness to meet strength conditions shall prevail. When high pressure melt injection mold, the mold cavity of some of the mating surface will produce clearance, clearance is too large, a flash, at this time should be based on the characteristics of the plastic viscosity on the premise of do not produce material overflow, will allow the biggest gap as a condition of the rigidity of the cavity.

plastic pieces of the convex platform, grooves or between convex platform with grooves between the distance between center line is called the center distance. As a result of the center distance tolerance is two-way contour tolerance, at the same time, the result of wear and tear will not make the center distance size changes, don't have to consider when calculating the wear volume. Mold center distance is by forming holes or install core hole center distance. Core and template for clearance fit, fit clearance can produce fluctuations affect parts center distance, then should make clearance error and manufacture error accumulation value is less than the required parts center distance tolerance.

by the strength and stiffness calculation to determine the cavity wall thickness, especially for high precision or large mold cavity, more can't simply by experience to determine the thickness of cavity wall and bottom plate. Mold cavity wall thickness calculation and the maximum pressure shall prevail. Maximum pressure is generated at the moment of the melt filled cavity in injection molding. As the plastic cooling and gate freeze, the pressure in the cavity is gradually reduced, close to atmospheric pressure in the cavity.

thread parts out of the mold molding, radial size and pitch will be contractive decrescent. In order to make the thread parts with the standard metal better cooperate, improve molding plastics screw thread after screwing in performance, molding plastic parts of screw thread core type or ring radial size should be consider the influence of shrinkage, the appropriate to reduce the thread type ring radial size and increase the radial size of core. Threaded ring among the cavity size class size, and threaded core job dimensions as part of the core size.

because of the many different kinds of threaded connection, cooperating with nature also each are not identical, the factors affecting parts of threaded connection is more complex, thus to satisfy the requirement of the plastic screw thread with accurate is difficult, there is no plastic thread standard, also does not have mature calculation method. Because the thread pitch diameter of thread with nature is the most important parameters, he decides the thread can be screwing in sex and connection reliability, so the calculating mould threaded the size of large, medium and paths, are based on plastic thread pitch diameter tolerances.

to smoothly, demoulding cavity or core design draft. At this time, to calculate the cavity size, should be based on big end size, on the other side according to the draft corresponding to reduce, to calculate the core size, should end with small sizes as the benchmark, at the other end according to the draft corresponding increase, so easy to leave allowance when injection molding processing and repair the mold. When calculating the cavity depth and the height of the core size, due to the bottom cavity or core end surface wear is small, so can not consider the wear volume.

when the thread with more teeth, thread pitch cumulative error constriction, you must calculate the shrinkage pitch. Processing with irregular decimal type special pitch of thread ring or cores, can use to configure special teeth of variable speed on the lathe hanging wheel and other methods to carry on the processing. Plastic mold cavity by the melt in the process of forming high pressure effect, should have sufficient strength and rigidity. If the cavity wall and bottom plate thickness is too small, may be due to insufficient strength and plastic deformation and destruction, may also be due to insufficient stiffness of flexure deformation, lead to flash, flash and reduce plastic parts dimension precision and smooth demoulding.

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