In recent years, with the development of resin industry, mold industry and machine automatic control component manufacturing industry, the application range of injection molding products has been widely promoted and popularized. With the wide range of application of various modified plastics, engineering plastics and composite plastics, the requirements for the accuracy and complexity of plastic products are becoming higher and higher, so it is more and more important to select the appropriate injection molding machine.
1、 Factors affecting the selection of injection molding machine:
Generally, the important factors affecting the selection of injection molding machine include product weight repetition accuracy, mold opening position, cycle time, etc. Therefore, the following information must be collected or available before selection:
1. Product: size (length, width, height, wall thickness), net weight and total weight, etc.
2. Material: the proportion of raw materials or pelletized materials and other materials and crushed materials.
2、 How to select the model of injection molding machine
After obtaining the above information, you can select the appropriate injection molding machine according to the following steps:
Models and series are determined by products and plastics. When customers choose an injection molding machine, they should first determine the structural form of the injection molding machine according to the product removal direction and mold structure: vertical injection molding machine, angle injection molding machine or horizontal injection molding machine. There is little difference in the structural form of the glue injection machine of the main manufacturers, and the structural difference is mainly in the mold locking structure.
3、 Selection of mold locking force of injection molding machine:
The determination of the clamping force is determined by the design structure and plastic of the product mold. The mold locking force is an important parameter of the injection molding machine. When the high-pressure plastic melt fills the mold cavity, a large mold expansion force will be generated in the mold cavity, causing the mold to expand along the parting surface. If mold expansion is not allowed, the injection molding machine must provide a force greater than the mold expansion force to lock the mold, otherwise the phenomenon of edge overflow and material running will occur. This force is the mold locking force.
Too much clamping force will not only increase the customer's purchase cost, but also increase the wear of the mold and the difficulty of venting in the mold cavity, causing the products to be scorched or lack of materials. More importantly, when the machine is stressed, it will aggravate the wear of the machine, shorten the service life of the clamping mechanism and hydraulic system, and also cause a waste of energy. Therefore, when calculating the clamping force, it is necessary to calculate the customer's product projection area, the ratio of process length to wall thickness, materials Mold cavity pressure to calculate more accurate clamping force. The clamping force, like the injection volume, to a certain extent reflects the product processing capacity of the machine, and is often used as the main parameter to indicate the size of the machine specification.
4、 Select the appropriate injection molding model according to the mold
1. Connecting column (also known as guide column): the width of the overall dimension of the mold is determined by the internal spacing. The mold that can be accommodated by the large internal spacing of the guide column is also large, and the mold that can be accommodated by the small internal spacing of the guide column is also small. The minimum contact area between the mold and the template shall not be less than 60%, and the maximum effective area of the mold shall not exceed the area of the spacing between the connecting columns. Otherwise, it is easy to cause uneven stress on the engine template, local flash of the product, and the template is easy to crack.
2. Mold size: the mold is a ductile iron plate supported behind the mold, and the mold shall not exceed the internal distance area of the mold. To prevent the mold from bending during injection. Too small die will produce too high bending stress on the formwork, and even make the formwork break. When injecting thin-walled products, the injection pressure is high, the injection speed is fast, and the cycle time is short. The template should be thickened, and the reinforcing rib plate should be strengthened to increase the stiffness.
3. Capacity modulus: the minimum to maximum molds that the injection molding machine can accommodate. The difference between them is the adjustment modulus of the injection molding machine. The available mold thickness should be larger than the minimum volume modulus, so that the injection molding machine can open and lock the mold. Otherwise, special engineering shall be added (the effective thread of mold adjustment of the guide post shall be increased, and the minimum value of the program shall be changed). When the thickness of the same available mold is greater than the maximum capacity modulus, special engineering shall be considered (the rack and guide post and their threads shall be lengthened, the steel strip moved by the rack mold locking second plate shall be lengthened, and the maximum value of the program shall be changed.) However, there is an upper limit value for the increased volume modulus, and the bearing capacity of the guide post (the maximum bearing weight of the mold) should be considered. The maximum and minimum capacity modulus of the dumpling type injection molding machine are respectively the distance between the moving and fixed templates when the dumpling is straightened and the mold is adjusted to the maximum and minimum. This parameter determines the mold opening space and product depth. If the volume modulus is large, the product depth is deeper; On the contrary, the shallower the product depth is. The full hydraulic large-scale two plate injection molding machine has larger capacity modulus and mold opening stroke than the machine dumpling injection molding machine of the same level, which is more suitable for deep cavity products and high height products.