There are many factors that affect the shrinkage and deformation of plastic products in the mold and after the mold is released, such as temperature, injection pressure, materials, and holding time. The factors affecting plastic threads are more and more complicated. So far, from the data point of view, there is no mature method to solve the problem of plastic thread coordination. In order to better realize the processing and matching of the plastic thread, the following is a discussion on the problems of the plastic thread of the ordinary fastening connection, such as the metric thread of the cusp angle of 60° and the calculation of the size of the core and the ring of the square thread.
The threaded core is used to form the internal thread, and the ring is used to form the external thread. The calculation method is as follows:
The outer diameter, the median diameter and the inner diameter of the core thread can be calculated according to the following formula:
The outer diameter, the median diameter and the inner diameter of the type ring thread can be calculated according to the following formula:
However, the calculation of the core and the thread pitch of the ring, if it is done according to the above method, will inevitably produce a decimal. For example, the thread M75×3 of the ABS material has a pitch calculation of 3.02 mm. If the material is polypropylene, the pitch is calculated to be 3.06 mm. It is very difficult to machine the core or the thread of the ring on a lathe according to this pitch. However, since the difference between the calculation result and the original pitch is small (0.02 mm or 0.06 mm), the shrinkage ratio may not be considered in the pitch of the core and the ring thread.
In the case that the pitch of the thread core and the ring does not take into account the shrinkage rate, the screwing property and reliability of the product thread must be ensured. For this purpose, the diameter of the retaining ring thread can be changed, and the core thread is appropriately increased. The method of diameter (ie, increasing the diameter of the medium to fit the gap) to achieve the fit of the plastic thread. The increased value can be determined according to the diameter of the outer diameter of the thread and the material of the thread. Generally, it should be about 0.2-0.6mm. The formula for calculating the outer diameter, the medium diameter and the inner diameter of the core thread is as follows:
In practice, it has been found that the above calculation method is feasible for a cusp angle of 60° metric thread, but sometimes it does not work for a square thread. The reason for this is that the shrinkage and deformation occurring in the axial direction of the thread change the pitch so that the gap between the teeth of the mating inner and outer threads and the teeth is small or even without a gap, which makes it difficult to screw in or to be screwed in. In order to solve this problem, the author took the first process of machining the square tooth ring, and using this type of ring to machine the threaded product, and then measuring the pitch and the tooth width with reference to the threaded product to determine the width of the tool for processing the core thread. The width of the general tool should be smaller than the groove width (0.1 to 0.2 mm). The core machined with such a turning tool can solve the problem of the cooperation between the square threads.
The above discussion is about the calculation of the size of the core and the ring of the 60° metric thread of the cusp angle and the calculation of the size of the core and the ring of the square thread and the technical measures taken in the actual work. Practice has proved that this method is effective and has reference and promotion value.
Landscape Light,Waterproof Strip Lights,Colorful Strip Lights,Waterproof Flexible Led Strip Lights
Jiangmen Duramp Electric Co., Ltd , https://www.durampled.com