Plastic products are common in our daily living, such as the 3C products we use every day "mobile phone, computer shell", "computer keyboard"; daily household items "fresh-keeping box", "portable water bottle"; plastics are used in automobile and locomotive shell panels”, “furniture”, etc. The extent to which plastic materials are widely used is closely related to our daily living. What does plastic injection have to do with us? We would like to discuss what points should be paid attention to in plastic injection molding, and what processes are required for injection molding to produce the general the products we see in the markets? Let's find out!
What is plastic injection?
Plastic injection technology is mainly used to manufacture various plastic products that we see in our daily living. The principle of injection molding is to first heat and melt granular plastic pellets into a liquid and flowable state through an injection molding machine at high temperature, and then use high pressure mode. The molten plastic raw material is injected into the mold, and after a period of cooling down, the final plastic product is completed after the mold is finally opened.
Five plastic injection molding process
There are 5 stages of plastic injection molding: plasticizing, injection, pressure holding, cooling, demoulding. These 5 stages will continue to circulate in the manufacturing process, and with the trend of automated production, the required plastic products can be efficiently produced in large quantities .
1. Plasticization
The plastic raw material is melted at high temperature in the material tube, and the plastic processing temperature is set on the injection molding machine according to the characteristics of the selected plastic material, so that the plastic pellets are dissolved at the correct temperature.
2. To shoot
The plastic material is filled and injected into the mold through the screw, and the plastic is shaped by using the mold design space. At this time, the parameters of the injection machine must be adjusted according to the plastic injection molding conditions or the mold condition, which can avoid subsequent problems such as size mismatch and burrs.
3. Holding pressure
After the plastic raw materials are filled into the mold, continue to pressurize the space in the mold, mainly to ensure the tightness of these plastic raw materials and avoid the backflow of the raw materials.
4. Cool down
The product is quickly cooled and shaped in the mold.
5. Demoulding
Finally, the plastic product is completed, and the product is released from the mold.
Three key points of plastic injection molding
1. Dryness of plastic raw materials
Plastic raw materials are usually in the state of solid or elastomer at normal room temperature. During plastic injection processing, the raw materials will be heated, so that these solid plastic raw materials will be transformed into a molten liquid with fluidity and shape, so as to facilitate subsequent injection. When the finished product is formed, during the plastic injection process, special attention should be paid to the dryness of the plastic raw material. If the raw material with moisture enters the high temperature material tube, it is likely to make the plastic injection process unstable, and even affect the injection molding product. appearance and properties. Common raw materials in the industry include PP, PA, PE, PC, ABS, etc. In fact, some of the plastic raw materials have a small amount of moisture attached to the surface, such as PA and PC, which need to be additionally dried. Therefore, it is necessary to confirm which plastic raw material ingredients are used before the product is produced? And ensure the dryness of the plastic material before proceeding with the injection process.
2. Selection of injection molding machine
There are many types of plastic injection machines on the market. The choice of model is a key to plastic injection. Because the size, weight, and plastic materials of the products you want to create are different, the suitable injection machines will also be different. In addition to considering the nature of plastic injection products, we recommend that you also consider the mold opening stroke, clamping force, injection volume, screw compression ratio, injection speed, etc., to select the most suitable injection model for your product.
3. Adjustment of plastic injection parameters
In the process of plastic injection molding, the operation technology of personnel is very important. The so-called operation technology is actually to control the setting of injection parameters and make adjustments at any time. We divide the adjustment range of plastic injection parameters into 5 categories: "temperature", "pressure", "speed" ”, “position” and “time”, among which the temperature part is special and needs to be used to adjust the drying temperature of the plastic raw material, the heating temperature of the injection machine barrel, the cooling temperature of the mold, etc. Other parameters are set according to the steps of plastic injection and Each product’s injection status needs to be adjusted in detail in a timely manner. In the early days, the master would rely on feeling or experience when adjusting the machine. However, with the advancement of the technology era, the current injection molding machine can transmit real-time data to make parameter adjustments.
Applications of plastic injection
Construction
Injection molding various construction and building components is becoming increasingly popular due to the innate versatility of plastic injection molding. Some of the most commonly-produced elements in the construction industry include small and large accessories, fasteners, and various hand tools.
Food industry
Parts used in the food and beverage field must follow stringent health and safety rules and regulations, such as the GMA-safe program and FDA certification. All this is necessary to ensure the wellbeing of individuals using such products. To abide by the aforementioned standards, molded parts have to be BPA-free and completely non-toxic.
Medical industry
Similarly to the food and beverage industry, plastic parts made for the medical and pharmaceutical field have to follow even more stringent guidelines. In order to meet those standards, manufacturers must use FDA or medical-grade resins and manufacture their components according to ISO certification. What’s more, components for the medical field require various chemical properties, such as high tensile strength, resistance to very high temperatures, and others.
These components have to be both decorative and functional, which means the manufacturer has to achieve the balance between aesthetics, usability, and durability. The components you can create through plastic injection molding are so varied it’s difficult to name the most common ones. Some of the frequently used parts are product stops, hooks for pegboards, shelf dividers, but also many more.
Automotive components
Due to its innate design flexibility, but also high durability and longevity, plastic injection molded parts are very frequently used in the automotive industry. This process makes it easy to design and create various items you find in and on your car every day, such as mirror housings, cup holders, bumpers, but also entire dashboards.
Conclusion
Plastic injection is a processing method that can quickly produce plastic products. There are many points to be considered and paid attention to in the process of plastic injection molding. From the selection of injection models, plastic selection to mold making, they all need to undergo strict review and evaluation. In addition to the importance of selecting the injection model at the beginning, the plastic injection process also requires the cooperation of product designers and experienced technical operators to truly make perfect plastic products to be used in various applications.
