The manufacturing precision of molding parts is one of the important factors affecting plastic parts dimensional accuracy.
Molding parts machining accuracy is lower, the size of the injection molding processing accuracy is lower.
Mould in use process, because of the plastic melt flow scouring and stripping of the friction and the corrosive gas may be produced in the process of forming rust and due to the causes of forming parts grinding polishing surface roughness increases, it will result in changes of the molding parts size.
Wear cavity size larger as a result, core size smaller.
small core molding plastic pieces of the holes or slots.
Small core is made separately, and then embedded in the template.
For different core, in order to facilitate processing, often core design into two segments, the connection and a fixed period of circular, connected by convex shoulder and templates.
Thread core and ring are respectively used for molding plastic pieces of the set piece of female and male activity.
In addition, the threaded core and the thread type ring can also be used to fixed with screw hole and screw insert.
factors affecting plastic parts dimension precision is very complex, these factors should be used as the basis for determine the forming parts work size.
After plastic molding shrinkage rate and the variety of plastic, plastic pieces of the shape, size, thickness, mold structure, molding process conditions and other factors.
In the mold design, it is difficult to accurately determine the shrinkage, because there are differences between the actual shrinkage rate and calculated shrinkage rate after molding, production process conditions change, batch change also cause plastic shrinkage rate fluctuations, these can cause the change of size of plastic parts.
thread core can be divided into direct molding plastic parts according to the use and fixed nut insert two threaded holes.
Two cores on the structure principle of distinction, used for plastic forming parts of threaded hole thread core must be considered in the design of plastic shrinkage rate, surface roughness, the beginning of the thread, the end will be designed according to the requirements of the structure of the plastic screw thread.
And fixed nut insert thread core don't have to consider of plastic shrinkage rate, according to the common thread can be made.
thread core installation within the mold, molding to reliable positioning, not for clamping vibration or the impact of the material flow and produce mobile, open mold with plastic parts can be removed and is convenient for loading and unloading.
Common thread type ring structure with integral and modular two.
Integral thread ring precision is high, but the loading and unloading time consuming;
Combined ring by two disc split, two disc with a guide pin positioning in the middle.
After molding plastics external thread left to trim the spell joint, only for the occasion of thread accuracy is not high.
punch and core are the inner surface of injection molding processing parts.
Punch generally refers to the plastic forming parts in the larger, main parts, its inner cavity therefore also known as the main core, core generally refers to the hole and slot parts in plastic forming parts.
The main core according to the structure can be divided into integral type and combined two kinds, simple in integral is mainly used for small die core.
General mold core are separate processing, and then inserted into the template.
Using some structure or the core circumferential or axial positioning.
For the convenience of processing, the core of complex shape is used mostly with spell type composite structure.
directly on molding parts work size refers to the forming parts is used to constitute the dimension of the plastic parts, main cavity and the depth of the radial size of core and cavity size and the height of the core size, between the core and core size, etc.
Any plastic parts have a certain amount of geometry and dimensional accuracy requirements, if any, fit the requirements of size, higher accuracy.
In the mold design, should be determined according to the dimension precision of plastic parts molding parts working size and precision grade.
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