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Automotive Injection Mold Analysis
Jun 05, 2018

The core hint: In the development of the automotive industry, the demand for plastic parts is increasing day by day, because the application of plastic parts to the construction of automobiles is very high, which means that the quality of plastic parts has a tremendous role in the development of the automotive industry. The need for plastic parts in the production of quality assurance, and determine the quality of plastic parts is the mold, due to the mold of the things that make out of the plastic parts in the application process to cause losses in various fields is not a small number of cases, so the production The study of plastic molds for the purpose of improving the quality and efficiency of plastic parts is very helpful for China's economic development.


We all know that the application of plastic parts to automobiles is very dependent on them. At the same time, as automotive products are continuously updated, only the key difficulties in the production of plastic parts for molds can make mold production meet the development needs of the automotive industry.


Injection mold design basis


1.1 Plastic product design is the focus


Plastic products are absolutely a key link in the design of plastic injection molds. The requirement for plastic products is nothing more than simplifying the model of plastic products as much as possible. Especially, it is better not to appear in the design of plastic products.


The simple design requirements of plastic products are a general direction, because there are many small links in the design of plastic products. The simple design is a requirement for every detailed link of plastic products, and meets the requirements on the basis of each The basic requirements of the link, such as the thin and thick design of injection molds, must be as uniform as possible in the evolution of the wall thickness of the mold to avoid inappropriate thick and uneven thickness of the glue. The rigidity and hardness also need to meet the standards, which is a key link to ensure the quality of plastic parts.


1.2 Classification of Plastic Products in Structural Design


The inside and outside surfaces of the plastic product must have a draft angle that conforms to the demoulding standards, which is more conducive to demoulding. In order to make the appearance smooth, the mold release is not hindered by friction, and the plastic product is as streamlined and smooth as possible in arc and texture. Plastic products have sharp corners. These corners are all rounded corners. The curvature around the inner and outer sides of the plastic product must be large. This is necessary.


The basic requirements of a forming mold for parts


In the strength and hardness to reach a certain standard, or can not withstand the friction, will affect the construction quality, the minimum hardness requirements can not be less than HRC35, very few special requirements in the hardness requirements of 50 ~ 52HRC above, the product after molding to make The surface is shiny, which can be achieved by polishing. In addition, there is a cavity part that needs to be polished. The sample of the product can not deviate from the product requirements, and then the production efficiency can be improved and the cost can be saved through the management and construction technology.


 Clear cavity number


The method of determining the number of cavities can utilize the entire injection machine, and then confirm the amount by the amount of injection and the nominal clamping force of the injection machine. In the process of carrying out the number of model cavities, it needs to be combined with other factors, such as: molding process, precision and maintenance, and economy.


Look for fractal lines and mold parting surfaces


The determination method of the fractal line can be determined according to the shape of the part. The function of the fractal line is nothing more than to divide the product into two parts, the existence of the same dividing line. The two parts that are divided into one are located in a fixed mold and the other is a part of a dynamic mold. To obtain the parting surface of the mold, it is possible to use the fractal line and scan the circumference of two molds with the fractal line to determine the parting surface of the mold.


4.1 Design Considerations for Parting Surfaces


The sub-profile surface, in the face of the sub-division surface generally requires a 3 to 5 degree penetration angle, the angle can not be less than 1.5 degrees. Sometimes there will be more than one step surface in a parting surface at the same time. In this case, using the same angle to act the angle A, this can make the processing easier and more convenient.


One part of the parting surface of the mold needs special attention, that is to ensure that each one has a sealed distance from the same surface, but also need to guarantee the effectiveness of the distance, so that the plastic melt can not easily flow out during the injection process, the sealing distance This name corresponds to this performance and can be blocked. In the creation process of the parting surface, if you encounter a parting surface with a large difference in height, such as a curved surface or an inclined surface, or a step, whether it is one or more, a reference plane must be set for it, which can facilitate processing and measurement.


4.2 Fundamental Design Principles


Molded plastics need to be retained on the mold halves after the mold is opened. Of course, in the case where there is an ejecting mechanism as a precondition, the ejector mold half molds are usually movable molds, and only the ejector mold half molds appear under very few special circumstances. On the fixed mold.


Some plastic products will come with metal inserts. Since the inserts do not have the function of shrink-wrapping punches, the shape of the cavity is usually on the side of the moving mold. If not, the plastic products will be in the fixed mold area after the mold is opened. Once this happens, demoulding can become very difficult. If the concentricity structures are both inside the moving mold or the fixed mold, if the two models are molded on both sides, it is difficult to ensure the accuracy of the coaxiality. This is mostly due to manufacturing errors and assembly errors. Caused.


There is a certain requirement for the locking of the mold. This requirement must be met. In order to meet this requirement, plastic products are generally placed at the closing position of the movable mold, and the direction of the projected area is selected to be smaller, and the projected area is larger. Used for lateral fractal surfaces. This can greatly reduce the degree of locking force, in addition, the mold surface sometimes appears curved surface, when this phenomenon occurs must be added to the positioning mechanism, in the selection of the parting surface, as far as possible in the shape of plastic products The choice of parts, if plastic products in the shape of the ridge line and tangent, is not suitable for the selection of the parting surface.


Selecting the parting surface must be relatively smooth and without obvious sharp corners. This division will not affect the quality and appearance. Although it is not absolute, the probability of occurrence is still too large. It must be reasonable to arrange the size and number of inserts.