How to choose the right injection molding machine
2021-11-17
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 application of various modified plastics, engineering plastics and composite plastics, the requirements for the accuracy and complexity of plastic products are higher and higher, and the selection of appropriate injection molding machine becomes more and more important.
1、 Factors affecting the selection of injection molding machine:
Generally, 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 granulated 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, angular injection molding machine or horizontal injection molding machine. There is little difference in the structural form of glue injection machines of major 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 clamping force is determined by the design structure of product mould and plastic. The mold locking force is an important parameter of the injection molding machine. When the high-pressure plastic melt fills the cavity, a large mold expansion force will be generated in the cavity, causing the mold to expand along the parting surface. If the 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 overflow and material running will occur. This force is the mold locking force.
If the clamping force is too large, it will not only increase the purchase cost of customers, but also increase the wear of molds and the difficulty of venting in the mold cavity, resulting in scorching 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 more accurate clamping force through the customer's product projection area, the ratio of process length to wall thickness, material and mold cavity pressure. The clamping force, like the injection volume, reflects the product processing capacity of the machine to a certain extent, and is often used as the main parameter to represent 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 inner spacing determines the width of the overall dimension of the die. The inner spacing of the guide column is large, and the molds that can be accommodated are also large, and the inner spacing of the guide column is small, and the molds that can be accommodated are 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 in the connecting column. Otherwise, it is easy to cause uneven stress on the engine template, flash occurs in part of the product, and the template is easy to crack.
2. Die size: the template is a nodular cast iron plate supported behind the mold, and the mold shall not exceed the inner distance area of the template. To prevent the mold from bending during injection. If the die is too small, it will produce too high bending stress on the template, and even break the template. 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. Volume modulus: the minimum to maximum molds accommodated by the injection molding machine. The difference between them is the modulus adjustment 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 mold adjustment effective thread of the guide post shall be increased, and the minimum value of the program shall be changed). Similarly, when the thickness of the available mold is greater than the maximum volume modulus, special engineering shall be considered (the frame and guide column and their threads shall be lengthened, the steel strip moved by the second plate of the frame mold locking shall be lengthened, and the maximum value of the program shall be changed.) however, there is an upper limit value for increasing the volume modulus, and the bearing capacity of the guide column (the bearing weight of the maximum mold) shall be considered. The maximum and minimum volume modulus of the dumpling 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 bulk modulus is large, the deeper the depth of the product is; On the contrary, the shallower the depth of the product. The capacity modulus and mold opening stroke of the full hydraulic large two plate injection molding machine are larger than those of the same level of dumpling injection molding machine, which is more suitable for deep cavity products and high height products.
1、 Factors affecting the selection of injection molding machine:
Generally, 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 granulated 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, angular injection molding machine or horizontal injection molding machine. There is little difference in the structural form of glue injection machines of major 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 clamping force is determined by the design structure of product mould and plastic. The mold locking force is an important parameter of the injection molding machine. When the high-pressure plastic melt fills the cavity, a large mold expansion force will be generated in the cavity, causing the mold to expand along the parting surface. If the 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 overflow and material running will occur. This force is the mold locking force.
If the clamping force is too large, it will not only increase the purchase cost of customers, but also increase the wear of molds and the difficulty of venting in the mold cavity, resulting in scorching 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 more accurate clamping force through the customer's product projection area, the ratio of process length to wall thickness, material and mold cavity pressure. The clamping force, like the injection volume, reflects the product processing capacity of the machine to a certain extent, and is often used as the main parameter to represent 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 inner spacing determines the width of the overall dimension of the die. The inner spacing of the guide column is large, and the molds that can be accommodated are also large, and the inner spacing of the guide column is small, and the molds that can be accommodated are 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 in the connecting column. Otherwise, it is easy to cause uneven stress on the engine template, flash occurs in part of the product, and the template is easy to crack.
2. Die size: the template is a nodular cast iron plate supported behind the mold, and the mold shall not exceed the inner distance area of the template. To prevent the mold from bending during injection. If the die is too small, it will produce too high bending stress on the template, and even break the template. 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. Volume modulus: the minimum to maximum molds accommodated by the injection molding machine. The difference between them is the modulus adjustment 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 mold adjustment effective thread of the guide post shall be increased, and the minimum value of the program shall be changed). Similarly, when the thickness of the available mold is greater than the maximum volume modulus, special engineering shall be considered (the frame and guide column and their threads shall be lengthened, the steel strip moved by the second plate of the frame mold locking shall be lengthened, and the maximum value of the program shall be changed.) however, there is an upper limit value for increasing the volume modulus, and the bearing capacity of the guide column (the bearing weight of the maximum mold) shall be considered. The maximum and minimum volume modulus of the dumpling 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 bulk modulus is large, the deeper the depth of the product is; On the contrary, the shallower the depth of the product. The capacity modulus and mold opening stroke of the full hydraulic large two plate injection molding machine are larger than those of the same level of dumpling injection molding machine, which is more suitable for deep cavity products and high height products.
