In the development of the automotive industry, the demand for plastic parts is increasing, because the construction of the plastic parts of the application of plastic is very high, that is the quality of plastic parts of the development and construction of the automotive industry has a huge role in promoting, which requires plastic In the production of the need for quality assurance, and determine the quality of plastic parts is the mold, because the mold of things and made out of the plastic parts in the application process to the various areas of the loss of the case is not a few, so the production of plastic parts Mold to improve the quality of plastic parts, efficiency for the purpose of research, China's economic development is very helpful.
First, the basis of injection mold design
1.1 plastic product design is the key
Plastic products is definitely a key point in the design of injection molds, the design of plastic products, the requirements are nothing more than as much as possible to simplify the model of plastic products, especially the undulating design is best not to appear in the plastic products design.
Plastic products in the design of the simple requirements is a general direction, because the plastic product design has a lot of small links, simple design is a plastic products for each refinement of the requirements, on the basis of the requirements to meet the various Link the basic requirements, such as the design of the thick mold design, it is necessary in the evolution of the mold as much as possible to achieve uniformity of the wall thickness, to avoid inappropriate thickness of uneven glue bit. In the stiffness and hardness also need to meet the standards, which is to ensure the quality of plastic parts of a key link.
1.2 Classification of plastic products in structural design
Plastic products on both sides of the inside and outside have to meet the stripping standard stripping slope, which is more conducive to stripping. In order to make its appearance smooth, stripping from friction and obstruction, plastic products as far as possible in the curvature and texture to do streamline and smooth. Plastic products have sharp corners, these corners are rounded, for the curvature of the plastic products inside and outside the sides of the circumference of the corner, the curvature of the arc should be larger, it is necessary.
Second, a molding die on the basic requirements of the parts
In the strength and hardness to achieve a certain standard, or can not withstand the friction, will affect the construction quality, the hardness requirements of the minimum can not be lower than the HRC35, very special requirements in the hardness of the requirements of 50 ~ 52HRC above, The surface is shiny, can be achieved by polishing, the other needs to be polished part of the cavity, the product sample can not deviate from the product requirements, and then through the management and construction technology to improve production efficiency and cost savings.
Third, clear the number of cavity
The method of determining the number of cavities can take advantage of the total injection machine and then confirm how much it is by the amount of injection and the rated clamping force of the injection machine. In the process of the number of models need to be combined with other factors to complete, such as: molding process, precision and maintenance and economy.
Fourth, look for fractal lines and mold parting surface
Fractal line to determine the method can be determined according to the shape of the part, the role of fractal is nothing more than the product is divided into two parts, the same line of existence. Divided into two parts of a fixed molding, dynamic mold is another part of the molding. To get the mold parting surface can use the fractal line, with the fractal line in the two mold around the scan can determine the mold parting surface.
4.1 Partial design considerations
Step shape surface, in the face of the step surface generally need to have 3 to 5 degrees of insertion angle, angle can not be less than 1.5 degrees. Sometimes a sub-surface will appear in a number of steps at the same time, in this case, with the same angle to the role of angle A, which makes the processing can become more simple and convenient.
There is a need to pay special attention to the parting of the mold, that is, to ensure that each surface has a sealed distance, but also need to protect the effectiveness of the distance, so that the plastic melt in the injection process is not easy outflow, This name is because of this performance and corresponding, you can lock the goods. In the creation of the parting surface, if you meet the surface or slope and the level of the difference between the height of the larger parting, whether it is one or more, you must set the datum plane, which can facilitate processing and measurement.
4.2 Basic principles of parting design
Shaped plastic in the mold after the need to retain on the mold, of course, this is the introduction of institutions as a prerequisite for the situation, the general launch of the semi-modal institutions are dynamic mode, only a very special circumstances, On the mold.
Some plastic products will be attached with metal inserts, because the inserts do not have the function of shrink wrap punch, shape cavity design is usually in the dynamic mode side, if not set, then open the mold will make plastic products in the mold area, In the event of such a situation, stripping will become very difficult. In the coaxial structure are in the dynamic or fixed mold internal, if the two models on both sides of the shape, coaxial degree is difficult to guarantee its accuracy, this situation is due to manufacturing errors and assembly errors Caused by.
The lock of the mold is a certain requirement, the request must be met, in order to meet the requirements of the ground in the geometric model of the plastic mold placed in the mold, the direction of choice to choose a smaller projection area, the projection area of the larger direction For lateral fractures. This can greatly reduce the locking force, in addition, the parting surface sometimes appear surface, when this phenomenon must be added to the positioning mechanism, the choice of the parting surface as much as possible not to affect the appearance of plastic products Of the choice of parts, if the plastic products in the shape of the line and tangent line, nor is it suitable for the choice of parting.
Select the parting surface must choose a relatively smooth and no obvious sharp corners, so that the division will not affect the quality and shape, although not absolute, but the probability is still too large. Be sure to arrange the size and number of internal mold inserts.