Analysis: China's automotive plastic parts applications and advantages
December 23, 2022
The special appearance and size requirements of injection molded parts for automotive complex components have increased the threshold for the development of automotive injection molded parts and the risks involved. Moldflow 3D software helps companies analyze the molding feasibility of plastic parts at the product design stage, evaluates and optimizes product design through the analysis of parts deformation and molding process, and guides downstream manufacturers' mold and injection molding optimization.
Because the plastic parts of automobile complex parts have unique characteristics, the injection molding needs to fully consider the following factors: drying treatment of materials, new requirements for screw of glass fiber reinforced materials, driving forms, and mold clamping structure. Wait.
First of all, when the commonly used resin materials such as bumpers and dashboards are modified resins such as modified PP and modified abs, the resin materials have different moisture absorption properties to meet the water content requirements during molding (general requirement 0.2). Before entering the injection molding machine screw pre-molding measurement, the resin raw materials must be dried by hot air or dehumidified and dried. The modified PP (PPEPDM) resin is less hygroscopic and generally uses a hot air dryer at 80-100°C for 2-3 hours. The modified ABS (PCABS) has a strong hygroscopicity. Before the molding and drying, the desiccant dryer is used for the desiccant drying treatment. We have fully considered the function of the dehumidifying and drying system in the design of automotive molding systems for complex plastic parts.
Secondly, at present, the domestic automotive plastic parts are basically glass-fiber-reinforced plastic products. Compared with the use of chopped glass fiber-reinforced resins, the material and structure of the screw of injection molding machines used to form glass fiber-reinforced plastic parts are not limited. Big difference. When the injection molding machine is designed, it is necessary to pay attention to the alloy material of the screw barrel and the special heat treatment process to ensure its corrosion resistance and strength.
Third, because the automotive parts and conventional products are different, its cavity surface is very complex, the stress is not equal, the stress distribution is uneven, in the design, it needs to consider its processing capacity. The processing capacity of the injection molding machine is reflected in the mold clamping force and the injection capacity (indicated by the maximum theoretical injection volume). When the injection molding machine is molding a product, the mold clamping force must be greater than the mold opening force generated by the mold cavity pressure, or the mold parting surface will be separated to generate flash.
The formula for determining the mold clamping force of the injection molding machine is as follows: P mold clamping P cavity F/100. In the formula: P mold clamping mold clamping force (or clamping force) KN; P cavity mold cavity average pressure , MPa, and product structure shape, accuracy requirements and number of cavity per model and so on, the value range is generally between 25-40MPa; F mold cavity, horizontal overlap projection area of the runner and feed inlet CM3.
In order to ensure a reliable clamping, injection molding process clamping force must be less than the injection molding machine rated clamping force. The maximum theoretical injection volume of the injection molding machine matches the tonnage of the mold clamping force of the injection molding machine. It is the injection capacity of the injection molding machine that is nominally based on polystyrene (PS) before delivery.
Fourthly, according to the characteristics of automobile complex plastic parts, the drive form of the injection molding machine and the design of the mold clamping mechanism are currently used hydraulically mechanically or fully hydraulically. Institutional injection molding machine. After many years of efforts, Terry Machinery Co., Ltd. broke through the traditional constraints and developed a mechanical structure with two-plate clamping and direct compression and composite clamping. The advantage of this structure is that its open stroke is far greater than the hydraulic toggle clamp structure, at least more than 2 times, to meet the production needs of large automotive plastic parts (such as bumpers, dashboards, etc.). Secondly, the mode locking uses four composite oil cylinders to lock synchronously, and the large-tonnage smooth clamping is realized with a small flow rate. The clamping force can be higher than the hydraulic toggle clamp structure with the same tonnage. Accurately guarantee the precision of molding composite surfaces of large-scale complex plastic parts of automobiles.
Fifth, because the cavity surface of auto parts is very complex, the injection molding machine must consider its particularity when designing, and configure some special function programs: such as multi-group core pulling function, timing control function, injection molding machine matching mold changing device function , matching pick-up robot device features. These special features have obvious advantages in producing automotive plastic parts. For example, in order to shorten the production cycle, this type of injection molding machine is used to automatically remove the large-scale plastic product parts after the mold is ejected by the pick-up robot, and the multi-group pull cores make the large-scale plastic products steadily integrated. Out, no whitening or cracking. At present, most of the robots used in this injection molding system are 3-axis pick-up robots and 6-axis pick-up robots.
Advantages of Plastic Parts for Vehicles Advantages of Automotive Complex Plastic Parts:
1. The plastic can be processed at one time. The processing time is short and the accuracy is guaranteed.
2. The elastic deformation characteristics of plastic products can absorb a large amount of collision energy and have a large buffer effect on strong impacts, thus protecting the vehicle and the occupants. Plastic car dashboards and steering wheels are used in modern cars to enhance cushioning. Front and rear bumpers and body trims are made of plastic to reduce the impact of objects outside the vehicle on the body. Plastic also absorbs and attenuates vibration and noise, improving ride comfort.
3, plastic corrosion resistance, local damage will not corrode.
4, through the addition of different fillers, plasticizers and hardeners to produce the desired properties of plastic, in order to meet the requirements of different parts of the vehicle. More convenient is that the plastic color can be changed to different colors by additives, eliminating the need for painting. Some plastic parts can also be electroplated.
Shenyang Zhongda Huanxin Refrigeration Technology Co., Ltd.
