What is the impact of injection molding process on product function?

Plastic materials are taking up a higher and higher proportion in daily life, and the regulations for their quality are also getting higher and higher. The injection molding process is a key manufacturing method, and it is more and more urgent to improve the technology, more factors are affecting the products of the injection molding process, but the standard of the production process of the injection molding process is one of the key influencing factors, and the following may introduce in detail the hazards of the main parameters of each processing process for the characteristics of the products.

Traditional stamping tooling and processing process basic parameters depend on the working experience and methods of designers, and the rationalization of stamping tooling depends only on continuous trial parts and mold repair, and the setting of processing process main parameters can only rely on continuous trial parts to carry out changes, which lacks scientific proof and results in long production and manufacturing time, increased costs, and ensure quality.

The simulation of the whole process of forming can identify the problems in the design scheme before the processing of the die so that the basic parameters of the stamping die and processing process can be created above the basic analysis of scientific research, which can reduce the production cycle and improve the quality of the products. Along with the improvement of product quality regulations, the predictive analysis of the whole process of molding has become a stage that cannot be lacking in the design plan. Therefore, the creation of a mathematical analysis model of melt flow and heat transfer in the core of the whole process of injection molding, and the use of the scalar simulation method to complete the simulation of the whole process of molding has a key practical significance.

Because the main parameters of the whole molding process immediately determine the fluidity of the melt in the mold core, which has the most immediate and long-term harm to the quality of the products, it is important to find the optimal processing criteria for product molding and carry out processing process manipulation for the whole molding process to improve the quality of plastic products.

This is because of the whole process of molding, fine molding machinery, and equipment. Effective stamping dies and quality raw material characteristics can only be reflected in the effective forming process settings, on the other hand, forming machinery and equipment. On the other hand, the shortcomings of the molding equipment, stamping dies, and raw material characteristics can sometimes be filled by a suitable molding process setting. It is easy to see that the injection molding process has a particularly important effect on the quality of the product.

Injection molding standards and hazards

1. Injection molding process pressure

Injection pressure refers to the pressure applied by the extruder screw tip or plunger pump to the plastic melt during the entire injection process. Its effect is to mix and melt the wear-resistant material, and the extruder screw (or plunger pump) must produce the frictional resistance to the flow of solid particles and wear-resistant material in the barrel and nozzle. The injection pressure has the effect of compacting after the die is filled with the melt at a certain rate.

In turn, it promotes the high density of the plastic part, and carries out the replenishment of the wear-resistant material caused by the cooling, thus maintaining the precise appearance of the plastic part and obtaining the necessary characteristics. The injection pressure is determined by the type of plastic, the type of plastic machine, the temperature of the mold shell, the mold design, and the thickness of the plastic part.

2. Holding pressure

When the melt fills the concave mold, the injection pressure plays the role of tamping for the melt in the structure, then we call the injection pressure also holding pressure. When the holding pressure is the same as the injection pressure, the shrinkage of the part is usually reduced, and the reliability of the part and its physical properties are ensured.

However, it is often difficult to get the part out of the mold due to the increase in internal stress at the mold exit. This makes the part very susceptible to deformation. The surface layer is scratched, etc., and it is also very easy to make the plastic part cause burr, which endangers the quality of conduction rate. Therefore, all aspects must be taken into consideration when selecting the holding pressure and selected carefully.

Generally speaking, the quality hazard of holding pressure on products is similar to that of injection pressure. Most of the plastic holding pressure in the middle of the injection pressure, and the actual holding pressure is clear, the key to consider the characteristics of the raw material of the plastic parts and the structure of the product, and to get rid of the friction resistance of the melt from the barrel to the core of the mold mobility, wear-resistant materials into the concave mold and will be compacted.

3. Melt pressure

Melt pressure is the pressure that the wear-resistant material at the tip of the extruder screw needs to suffer when the extruder screw is backed up. The key to the harm it causes to injection molding is reflected in the actual effect of the injection machine on the melt of the raw material and the melt working capacity. Generally speaking, by expanding the melt pressure, the rate of extruder screw reversal decreases, and the pressure on the melt in the barrel increases. As a result, the cutting efficiency of the melt is increased and the actual melting effect is improved.

However, it is important to note that, in addition to expanding the condensation type, too high melt pressure reduces the melt volume due to the return and leakage of the melt at the edge of the screw groove on the one hand, which is likely to cause insufficient metering check, on the other hand, it will make the cutting heat too high shear stress, which may dissolve the raw material and cause vapor bubbles or scalding, and endanger the quality of plastic parts.

4. Mold temperature

The temperature of the mold shell is the temperature of the surface layer of the mold core during the whole process of forming, and the temperature of the mold shell endangers the individual behavior of the melt's mold filling fluidity. The cooling rate of the product and the characteristics of the product after molding. The key to the setting of the mold temperature is the viscosity of the wear-resistant material. The lower viscosity of the wear-resistant material can be injected at a lower mold temperature to reduce the cooling time and increase productivity. For high viscosity abrasion-resistant materials, high mold temperature injection molding should be used.

Generally speaking, raising the mold temperature can make the cooling speed of the product uniform and avoid molding shortcomings such as pits and cracks. The mold temperature manipulation of crystalline plastics immediately determines the cooling rate, which further determines the speed of crystallization. Mold temperature is high when the cooling speed is small, the crystallization speed increases, beneficial to the molecular structure of the relaxation of the whole process, the molecular structure tends to be small utility. If the mold temperature is too high, it will increase the forming cycle time and make the goods brittle.

If the mold temperature is low, the cooling speed is large, and the fluidity and crystallization of the wear-resistant material proceed smoothly because the waiting time of the wear-resistant material in the crystallization temperature zone is reduced, which is unfavorable to the growth and development of crystallization, resulting in the low degree of crystallization of the molecular structure of the commodity and jeopardizing its performance index. In addition, the mold temperature is too low, the plastic melt fluidity friction resistance is very large, the water flow slows down, and even in the filling mold condensation prevent afterward into the material, prompting the product short shot, forcing tendency is large, often lead to plastic parts under the material. Dent. The fusion seam and other shortcomings.

5. Barrel temperature

To better ensure that all the normal fluidity of the plastic melt in addition to not making it produce mold dissolution, must be suitable for the selection of barrel temperature, the average molecular quality of large, molecular mass throughout and more centralized plastic and its laminated glass elastomer materials should be selected for higher temperature barrel temperature. Barrel temperature is generally arranged according to the front of the high after the low standard, but when the plastic with too much water cost time can also moderately enhance the back end of the development temperature.

6. Nozzle temperature

To better prevent the melt in the nozzle caused by the flow of delayed conditions, generally must make the nozzle temperature is slightly lower than the maximum barrel temperature, in the manufacturing of low-speed gears to the empty injection conditions, the spray out of the solution flow without bubbles, smooth as the temperature suitable for the specification.

7. Melt temperature

The key to melt temperature lies in the temperature of both the barrel and the nozzle, jeopardizing the melting of raw materials and the injection of melt to fill the mold. The increase in injection temperature is critical to improving the flow of the melt, which is related to many characteristics of the product. Increasing the melt temperature leads to thermal stress in the molded part. Impact compressive strength and tensile strain of the streamlined orientation. The physical properties of mechanical equipment, such as tensile strength, are reduced, while the impact compressive strength, tensile strain, and tensile strain of the vertically parallel streamline orientation are reduced. Length of fluidity. Roughness and other characteristics are significantly improved and can reduce the product after closing.

Generally speaking, raising the melt temperature is beneficial to improving the mold filling and its transmission in the core, reducing the tendency, etc., which is beneficial to the improvement of the overall performance of the product, but too high a temperature is not desirable. When the melt temperature is close to the upper limit of the injection molding temperature range, it is very easy to cause more vapor on the one hand, which will cause bubbles and cracks in the molded parts. Cracks. Color loss. Burning paste, etc., but also because too much to improve the circulation and cause burrs, endangering the product conduction rate quality, on the other hand, too high a temperature will make the plastic dissolution effect, so that the compressive strength of plastic parts to reduce the loss of ductility, etc., endangering performance indicators.

8. Injection time

Injection time manipulation injection speed is one of the main parameters.

The less the injection time, the higher the injection speed, the size of the injection speed is very harmful to the characteristics of the plastic parts. Increasing the injection speed can make the mold filling pressure increase, which is beneficial to the whole process of mold filling, and make the heat evaporation in the mold filling lower, the mold core temperature is more uniform, the product is uniform, and dense. In addition, it can reduce the shrinkage rate of the product, reduce the tendency of the core of the plastic parts, and improve the compressive strength of the fusion joint.

The increase of injection speed is beneficial to the comprehensive performance of the products, but too high injection speed will increase the pressure damage, reduce the dry solid layer thickness, increase the surface tendency of the plastic parts, and even make the melt produce ductile seepage so that the plastic parts are very easy to produce burrs. Surface cracks, etc.

It has been confirmed that both high and low injection speeds can cause a decrease in impact compressive strength. On the other hand, too low injection speed reduces the compressive strength at the fusion joint of the plastic part, tends to expand the total efficacy, and increases the thermal stress, which endangers the physical properties of the product.

9. Holding time

The holding time and the length of the cooling time also cause immediate harm to the quality of plastic parts. Reducing the pressure-holding time will accelerate the pressure reduction of the mold core, which may cause backflow and shrinkage of the plastic parts. This may cause drawbacks such as shrinkage, denting, and other disadvantages, and jeopardize the reliability of the part specifications.

By extending the holding time, the reliability of the molded part can be improved the above-mentioned defects can be prevented, and high-density products can be obtained. In addition, the core pressure is increased and the thermal stress caused by uneven temperature is changed. However, it increases the difficulty factor of mold existing, and sometimes it is very easy to scratch or bend the molded part by surface pressing.

The length of the melt time of raw materials can endanger the melt quality and immediately endanger the characteristics of the product. If the melt time is too short, it is not possible to melt uniformly. It is easy to cause lumps and bumps because of the uniform temperature. If the time is too long, the wear-resistant material will dissolve due to the effect of the extruder screw. It also hurts the product quality.

10. Unique processing hazards

Vibratory injection molding process, under high vibration pressure, along with the increase in vibration frequency, the product's pulling characteristics and vacancy impact compressive strength is significantly improved. In addition, the addition of the ultrasonic processing process can also have excellent practical effects.

Conclusion

Each of the main parameters of the process standard affects each other and not individually, and the shortcomings of some products are the result of mutual influence.