Part 1: Brief talk on the optimization design of injection molding machine platen
A brief talk on the optimization design of injection molding machine platen
Abstract: The various excellent properties of plastics have made them indispensable and important materials in many fields, such as the national defense industry, machinery, aviation, construction, medicine, etc. An injection molding machine is the main molding equipment for making thermoplastic or thermosetting materials into various shapes of plastic products using plastic molding molds. This article talks about the optimization and parameterization of the structure of the injection molding machine platen for reference only!
Keywords: injection molding machine platen optimization
The platen is the main body of the mechanical structure of the injection molding machine. The weight of the platen accounts for about 70% of the weight of the entire injection molding machine. According to the results of the finite element analysis and calculation, the structural topology optimization design of the key components of the injection molding machine can greatly reduce the raw materials and has excellent performance. Economic Value. Therefore, it is of great significance to optimize the design of the injection molding machine platen.
1 Structural topology optimization of platens
1.1 Overview of Structural Optimization
Structural optimization is the optimal design of the structure’s size, shape, topology, and layout by optimally distributing materials to the area of the predetermined structure with certain external loads and boundary conditions. Shape optimization is only the optimization of the boundary conditions of the structure; the topology of the structure is the spatial arrangement of the regions that make up the structure. Structural topology optimization is the most difficult in structural optimization, and topology can improve the performance of the structure. Optimizing the continuum structure is usually done by adjusting these parameters to change the shape of the boundary.
1.2 Topology Optimization of Discrete Structures
Topology optimization is the most difficult because many structural topologies need to meet certain functional requirements. The field to be designed is unknown, which is difficult to describe quantitatively or parameterize, which increases the difficulty of solving the problem. Later, numerical methods were introduced into this field, and the research on topology optimization became active again, and some analytical and numerical theories were put forward one after another. The base structure is a structure that is connected by many components, including all load application points and support points.
1.3 Topology optimization of continuum structure
1) Homogenization method continuum. It is the most widely used method in structural topology optimization. This method has been applied to the topology optimization of two-dimensional and three-dimensional continuum structures and the topology optimization of thermoelastic structures. It has been used in the design of composite materials. To generate composites consisting of intermediate-sized unit cells to expand the design space due to the elastic properties and density of macroscopic materials, this achieves a unified and continuous topological size optimization model of the structure.
2) Variable thickness method. This method is a geometric description method. The seven theoretical bases are that the element thickness in the base structure is used as a topology design variable, and the optimal topology is determined by analyzing the thickness distribution in the results. Topological optimization problems of thin plate and shell structures cannot be used for topology optimization of three-dimensional continuum structures.
Part 2: Solution to the slippage of the injection molding machine platen
The best solution to solve the slippage of injection mold
A threaded screw sleeve (wire screw sleeve) is a new fastener, a spring-shaped inner and outer thread concentric body precisely machined from stainless steel wire with a high-precision diamond cross-section. The thread set can meet the international standard of high-precision internal thread after the product, and its performance is better than the thread formed by tapping.
- It can form high-strength, wear-resistant, and high-precision standard internal threads when installed on mechanical parts of metal or non-metallic materials (such as aluminum, magnesium, and other light alloy engineering materials).
Typical applications: high voltage switchgear, hydraulic machinery, welding equipment, tobacco machinery, microwave communications, auto parts, air separation equipment, coal machinery, power machinery, textile, chemical fiber machinery, etc.
- When the thread processing is wrong, or the damaged internal screw hole is repaired, the threaded socket (wire screw socket) can be used as a repair method, which can be quickly and effectively repaired
Typical application: Repair after the threaded hole of various important parts is tripped, such as repair of the threaded hole of the injection molding machine platen.
- It is very convenient and fast to use the threaded socket for metric ←→ inch threaded hole conversion.
Typical application: imported equipment or mechanical inch threads need to be changed to metric threads due to the supply of spare parts.
Part 3: The principle of injection molding machine and the role of main parts
The working principle, technical parameters, and the function of the main parts of the injection molding machine
Section 1 Overview of Injection Molding Machine
Injection molding is a method in which thermoplastics or thermosetting plastics are uniformly plasticized in a heating barrel and then pushed into the cavity of a closed mold by a screw or plunger. Injection molding is carried out on an injection molding machine and is an important method for molding plastic products. Almost all thermoplastics and various thermosetting plastics can be molded by this method.
(1) Characteristics of injection molding
Injection molding can process plastic products with complex shapes and precise dimensions or simultaneously with metal inserts and long molding holes.
The molding cycle is short.
The surface roughness of the product is low, and the amount of post-processing is small.
High production efficiency and easy automation.
It has strong processing adaptability to various plastics and can produce some plastic products modified with fillers.
(2) Injection molding process
The injection molding process is that the thermoplastic or thermosetting plastic is heated, sheared, compressed, mixed, and conveyed in the heating barrel to make it uniformly plasticized (temperature, uniform molten state of components), and the plasticized molten material is in the nozzle. Under the blocking action of the mold, it accumulates at the front end of the barrel and then enters the closed low-temperature mold cavity through the pouring system of the nozzle and the mold with the thrust exerted by the screw or the plunger. After cooling and solidification, open the mold and take out the product; that is, a molding cycle is completed, and then the production process of the above cycle is repeated continuously. Take the screw injection molding machine as an example to illustrate:
1. Closing and locking the mold
The molding cycle of an injection molding machine generally starts when the mold is closed. The mold clamping mechanism of the injection molding machine completes the mold closing action. The mold clamping mechanism pushes the movable mold plate and the movable mold part of the mold to quickly close at low pressure (shortening the molding cycle). When the mold is completed quickly, the power system of the mold clamping mechanism automatically switches to low pressure. (Trying pressure) slow speed to protect the mold from damage. When it is confirmed that there is no foreign matter in the mold or the insert is not loose, switch to high pressure and low speed to lock the mold to ensure injection molding, and the mold is tightly closed when the pressure is maintained.
- Move the injection seat forward and inject
After the mold is locked, the injection seat moves forward, the nozzle is closely attached to the main gate of the mold, and then the injection cylinder generates high pressure. The melt at the front end of the barrel is injected into the mold cavity at high pressure and high speed, and the gas in the mold cavity is injected. It is excluded from the parting surface of the mold, and the pressure acting on the melt by the screw head at this time is called the injection pressure.
- Pressure holding
When the melt fills the mold cavity, to prevent the melt from reversing and the cooling effect of the low-temperature mold, the melt in the mold cavity will shrink in volume to ensure the compactness, dimensional accuracy, and mechanics, mechanical properties of the product. It is also necessary to maintain a certain pressure for the mold cavity to feed until the melt at the gate freezes. At this time, the pressure acting on the melt by the screw is called the holding pressure. The screw has a small advance due to replenishing the in-mold melt. 4. Product cooling and pre-plasticizing
- The injection seat retreats
- Open the mold and eject the product
After the product is fully cooled and shaped, the mold is opened. The product is automatically ejected under the combined action of the plastic machine’s ejection device and the mold’s ejection mechanism to prepare for the next molding process. According to customs, an injection molding cycle is called the working cycle of the injection molding machine.
(3) Structural composition of injection molding machine
A general-purpose injection molding machine mainly consists of an injection molding system, mold clamping system, hydraulic transmission, electrical control system, etc.
- Injection molding system
- Clamping system
- Hydraulic transmission and electrical control system
To ensure that the injection molding machine works accurately and effectively according to the predetermined requirements of the process (pressure, temperature, speed, time) and action procedures, the hydraulic transmission is mainly composed of various hydraulic components, hydraulic basic circuits, and other auxiliary devices. The electrical control is mainly composed of various It consists of various electrical components, instruments, electronic control systems (heating, measurement), and microcomputer control systems. The hydraulic transmission and the electrical control system are organically combined to provide power and control to the injection molding machine.
(4) Classification of injection molding machines
- According to the plasticizing and injection molding methods, it can be divided into plunger type and screw type
- The shape of the injection molding machine can be divided into vertical injection molding machine, horizontal injection molding machine, angle injection molding machine, and multi-mode injection molding machine.
- According to the processing capacity of the injection molding machine, it can be divided into ultra-small (clamping force 16T, injection volume 16CM3), small (clamping force 16-200T, injection volume 16-630CM3), medium (clamping force 250-400T, injection molding Quantity 800-3150CM3), large (clamping force 500-1250T, injection volume 4000-10000CM3), super large (clamping force 1600T, injection volume 16000CM3 or more), the characteristics of the clamping system can be divided into mechanical type, hydraulic type, and hydraulic-mechanical type.
Section 2 Basic Parameters and Model Representation of Injection Molding Machine
(1) Basic parameters of injection molding machine
The basic parameters of the injection molding machine can better reflect the size of the injection molding product, the functional ability of the injection molding machine, and the evaluation of the type, grade range, and product quality of the processed material. It is the injection molding machine’s design, manufacture, selection, and use. in accordance with.
1 Basic parameter of injection molding system
(1) Injection volume – the maximum injection volume achieved by the injection molding system when the injection screw or plunger makes a maximum injection stroke under the condition of air injection. This parameter reflects the processing capability of the injection molding machine to a certain extent. It marks the maximum quality of the plastic products that the injection molding machine can form. It is an important parameter of the injection molding machine. Generally, there are two ways to express the injection volume. Density ρ=1.05g/cm3) is expressed by the mass of the injected melt (g), and the other is expressed by the volume of the injected melt (cm3),
According to the definition, the theoretical value of the maximum injection capacity that the injection screw can inject at one time is the product of the maximum projected area of the screw head in its vertical and axial directions and the injection screw stroke. QL =π/4 D2S
The injection molding machine cannot reach the theoretical value during the working process because the density of the plastic changes correspondingly with the change in temperature and pressure. Therefore, the injection capacity needs to be properly corrected, and the corrected injection capacity is Q=αQL=π /4 D2 Sα,
α——Ejection coefficient, generally 0.7∽0.9,
Processing plastic products on injection molding machines, the quality of generic products, and the total amount of materials used in the gating system
It is better not to exceed 25%∽to 70% of the injection molding machine’s injection volume.
(2) injection pressure – the force of the end face of the screw or plunger acting on the unit area of the melt, the size of the injection pressure and the structure of the injection molding machine, the flow resistance, the shape of the product, the performance of the plastic, the plasticizing method, the plasticizing temperature, Mold structure, mold temperature, and product accuracy requirements are related. In actual production, the injection pressure can be adjusted within the allowable range of the machine. The size of the injection pressure should be selected according to the actual situation. The general injection pressure selection range is as follows.
A. The material has good fluidity, the product’s simple shape, the arm thickness is large, and the general injection pressure is less than 340∽540Kgf/cm2. It is suitable for processing LDPE, PA, and other materials.
B. The melt viscosity of the material is low, the product precision is general, and the injection pressure is 680∽980Kgf/cm2. It is suitable for processing PS, HDPE, and other materials.
C. The melt viscosity of the material is medium or high, the product precision is required, the shape is complex, and the injection pressure is 980∽1370Kgf/cm2. It is suitable for processing PP, PC, and other materials.
D. The melt viscosity of the material is high, the product is thin-walled, long process, high precision, complex shape, and the injection pressure is 1370∽1670Kgf/cm2. It is suitable for processing reinforced nylon, polysulfone, polyphenylene ether, and other materials.
E. When processing high-quality precision micro products, the injection pressure can reach more than 2260∽2450Kgf/cm2.
To meet the processing requirements of injection molding precision products or products with complex shapes and structural engineering parts, the injection molding machine processing adaptability is enhanced, the molding cycle is shortened, the product quality is improved, and the injection pressure has a tendency to increase.
(3) Injection time (injection speed) – the melt begins to cool after passing through the nozzle. To inject the melt into the mold cavity in time and obtain a dense, uniform, and high-precision products, the melt must be filled in a short time. In addition to sufficient injection pressure, the mold cavity must also have a specific flow rate; a parameter used to express the speed and slowness of the melt filling speed.