Thermoplastic Injection Molding
In the injection molding process of thermoplastic, the plastic raw materials mainly undergo physical changes, which makes the products reusable and environmentally friendly, and widely used in the field of sustainable development.
Injection Molding Company | Strict Manufacturing Process
Injection molding process mainly involves putting granular or powdery materials into the hopper of the injection machine, the raw materials are heated and melted into a flowing state. Pushed by the screw or piston of the injection machine, they pass through the nozzle The pouring system of the mold enters the mold cavity, and after cooling treatment, it hardens and shapes in the mold cavity.
For the production of injection molds, to achieve precise control of mold manufacturing, manufacturers generally need to pay attention to injection pressure, injection time, and temperature. The ABS injection molding process is mainly used in the production of thermoplastic plastics. In addition, some thermosetting plastics can also be used for injection molding, and the process has the characteristics of high efficiency and stable product quality.
For example: plastic injection molding of low anti-foaming plastic (density 0.2-0.9g/cm3) can produce plastic parts with excellent properties such as buffering, sound insulation, and heat insulation; two-color or multi-color injection molding can produce a variety of colors, beautiful appearance, and application Plastic products, which have obvious advantages in obtaining large plastic parts and reducing or eliminating condensation in the pouring system.
Advantages of Injection Molding Manufacturing Services:
- The injection molding process is generally suitable for companies that are eager to obtain molds and are ready to put them into production. This process has a short molding cycle and good production efficiency. For some emerging companies, it can easily realize automated production.
- For some relatively complex molds or products that require high precision, the injection molding process can produce plastic parts with complex shapes, precise dimensions, and metal or non-metal inserts. For the automotive industry, aerospace, and aviation, Production and manufacturing in the precision manufacturing industry play a big role.
- Generally, products manufactured through the injection molding process are of high quality, and both precision and hardness can be controlled through the process.
- Its application range is very wide. Among industrial products, injection molded products include kitchen supplies (trash cans, bowls, buckets, pots, tableware, and various containers), casings of electrical equipment (hair dryers, vacuum cleaners, food mixers), etc.), toys and games, various products for the automotive industry, parts for many other products, etc.
Generally, injection molding service companies mainly perform the following steps during the mold manufacturing process:
Preparation Before Mold Forming
To make the injection process go smoothly and ensure that the quality of plastic parts meets the standards required by users, generally, injection molding service companies will need to carry out some necessary preparations before injection, such as the appearance of the raw materials (such as color, particles, etc.) Size and uniformity) and process properties (fluidity, thermal stability, shrinkage) are inspected and measured. This is mainly used to determine whether the various properties of the raw materials are consistent with the required parameters or within the required range.
Injection molding companies will dye the raw materials. After getting the desired color, engineers will detect the moisture content and dry some water-absorbent plastics (Especially during ABS injection molding) to prevent the product from being removed after demoulding. During the production process, defects such as silver threads, markings, bubbles, and degradation may appear on the surface. If the service provider discovers decomposition in the plastic before molding, the barrel needs to be cleaned immediately;
Many molds require inserts before molding. To better embed the inserts into plastic products, service providers generally perform preheating treatment to prevent the plastic around the insert from cracking due to stress. For plastic parts that are difficult to mold, injection molding service providers should also prepare release agents in advance. Due to the different types and shapes of injection raw materials, the structure of the plastic parts, the presence or absence of inserts, and the use requirements, the preparations before molding various plastic parts are not the same.
Plastic Injection Molding Process
The injection process generally includes several steps: feeding, plasticizing, injection filling, and de-molding:
- Adding Ingredients
Since injection molding is an intermittent production process, injection molding companies need to add materials quantitatively as needed to ensure stable operation during the entire process, uniform plasticization, and ultimately obtain ideal plastic parts. If engineers perform improper operations, such as adding too much material or heating for too long, this can easily cause thermal degradation of the material and increase the power loss of the injection machine. If too little material is added, it will easily lead to a lack of pressure transmission medium in the barrel, and the pressure of the plastic melt in the cavity will decrease, making it difficult to feed (i.e., pressure compensation), which will easily cause defects such as shrinkage, dents, and holes in the plastic parts.
- Plasticization
When the plastic in the barrel is heated in the factory, it will change from a solid state (granular or powdery) to a viscous flow state. This process with good plasticity is called plasticization. The main factors that determine the quality of plasticization are the heating conditions and shearing effects of the material.
The requirements for plastic plasticization are: the plastic melt must be fully plasticized before entering the mold cavity. It must not only reach the specified molding temperature, but also the melt temperature must be uniform, and the content of thermal decomposition products must be minimized, It can provide enough molten plastic to ensure that the plasticization of the plastic is accelerated, and it also strengthens the mixing effect of the plastic to extend it to the level of polymer molecules (not just static melting). It changes the temperature distribution of the plastic melt. , the material composition and molecular morphology have changed and become more uniform. Therefore, the plasticizing effect of the screw injection machine is much better than that of the plunger injection machine.
- Injection Filling
Injection filling refers to the process of using a plunger or screw to push the plasticized plastic melt to quickly fill the mold cavity and to allow the melt to cool and solidify under pressure. The injection process can be divided into several stages such as mold filling, pressure holding, backflow, and cooling after the gate freezes.
- Demoulding
Demolding is the final step in an injection molding cycle. In this process, after the mold is cold-solidified by the cooling system, the factory needs to completely separate it from the equipment. This process seems simple, but it causes a lot of trouble for many injection molding companies. Irregularities in the molding process will have a great impact on the quality of plastic products. For example, when the operator performs the ejection step, the plastic product will be unevenly stressed, which can easily cause product deformation.
Generally, injection molding factories use two main methods of de-molding: ejector pin de-molding and stripper plate demolding. For these two molding methods, engineers will choose the appropriate molding method based on the structural characteristics of the product when designing the mold to ensure the quality and accuracy of the final manufactured product.
Not only that, for molds that use ejector pins for demolding process, the injection molding manufacturing factory needs to ensure process that the ejector pins are set as uniformly as possible, and their position should be selected at the position with the greatest de-molding resistance, and the place with the greatest strength and stiffness of the plastic part should also be selected. Prevent damage to the mold during molding. The stripper plate is generally used for the molding of thin-walled containers with deep cavities and transparent products that do not allow traces of push rods. The characteristics of this mechanism are large and uniform demoulding force, smooth movement, and no obvious traces left behind.
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