ABS Blow Molding
ABS blow molding raw material is a high strength, good toughness, and flexible processing polymer material. Its blow molded products have high strength, corrosion resistance, and high temperature resistance, and are often used to manufacture plastic shells for some chemical and medical instruments.
Blow Moulding Suppliers| Adjustment of Mold Parameters
Blow Moulding Suppliers| Adjustment of Mold Parameters
Blow moulding suppliers not only provide blow molding manufacturing services but also offer selection services based on the model of the mold and plastic blow molding machine. Usually, the purpose of the mold and the raw materials used for production need to be considered. The role of molds in the manufacturing process is undoubtedly the most crucial. Whether it is HDPE or ABS blow molding, a good mold can accurately and effectively blow out various products, such as bottles, containers, etc., for various materials.
Adjustment of Overall Parameters of Blow Molding Molds
When using blow molding molds, blow moulding suppliers need to coordinate them with the blow molding machine and adjust the overall parameters to fully utilize the functions of both.
- During the molding process of blow molding molds, the main requirement for the change in mold opening speed is to start slowly, then fast, and finally stop; The requirement for the change in mold closing speed is to start fast and then slow, and finally lock the mold. In general, the clamping mechanism of modern molds can adjust the speed. When adjusting the opening and closing speed of the blow molding equipment, the cycle speed can be adjusted faster when there are no parts, slower when the mold is about to close, and then locked to the bottom. When opening the mold, slow opening is used first. After the mold is opened for a certain distance, the fast opening can be used. After the mold is fully opened, stop and prepare for the next work cycle promptly. The characteristics of each product are different, and the adjustment of the distance between the slow opening and slow closing molds must be based on the premise of smooth molding and demolding of the product, to improve production efficiency without affecting the service life and performance of the equipment.
- In the production of blow-molded parts, the adjustment of the clamping force and locking force of the clamping mechanism is crucial. The clamping force will change with the structure, size, and type of raw materials of the mold. Blow moulding suppliers need to adjust according to the specific production parameters of the product. Generally, the clamping force should be lowered as much as possible on the premise that the product can be smoothly formed. This not only extends the service life of the clamping mechanism but also saves energy in the production process and improves efficiency.
- Mold temperature is sometimes a key factor determining production efficiency and product quality. In general, the temperature of the cooling water for the mold is around 10-30 ℃, but blow moulding suppliers need to adjust it promptly according to changes in temperature conditions. In areas with relatively humid climates, it is best not to condense the mold, otherwise, it will directly affect the quality of the plastic parts, and it is easy to corrode the mold, shortening its service life. When the temperature is not adjusted properly and condensation occurs in the mold, the blow moulding suppliers should promptly handle it, especially for high-surface quality blow molding molds produced in large quantities. At the same time, it is necessary to regularly check the cooling water channel for blockages or leaks.
- Although blow-molded products come in various shapes and qualities, the demolding of most parts is relatively easy. Some industrial parts with special and complex shapes may be difficult to de-mold. For the molding of such products, the mold opening time can be advanced and removed before the product has cooled down, to facilitate its demolding; At the same time, the temperature of the mold can be adjusted appropriately. Even if the product is difficult to de-mold, steel parts should not be used to lift it out to prevent wear and damage to the mold cut and cavity.
Adjustment of Blow Molding Pressure
When manufacturing molds, blow moulding suppliers need to consider in advance the various pressures that the mold needs to withstand during operation, such as injection pressure, plasticizing pressure, holding pressure, etc. If these pressures can be adjusted appropriately, it will greatly improve the quality of the formed plastic parts.
- Injection Pressure. Injection pressure refers to the pressure applied by the top of the screw to the material, mainly to reduce the resistance of the material from the barrel to the mold cavity, accelerate the speed of molten material filling, and compact the molten material to leave no gaps.
- Plasticizing Pressure. Plasticizing pressure, also known as back pressure, is a pressure set in the opposite direction to prevent the screw from retreating too quickly. The relief valve in the hydraulic system can adjust the magnitude of this pressure, and the magnitude of the plasticizing pressure directly affects the quality of the plasticizing process of the billet. If a large plasticizing pressure is maintained within an appropriate range, the material will be fully plasticized, resulting in smaller gaps in the molten material, which is beneficial for exhaust, but the molding cycle will be extended; If the plasticizing pressure is too high, even if it can improve the surface quality of the billet, there is still a certain possibility of causing defects such as discoloration and performance deterioration of the billet, and the energy consumption is also relatively high. In actual production, the lower the plasticizing pressure, the better, while ensuring the quality of the billet. Insufficient injection pressure can easily lead to an uneven surface of the billet, resulting in pits. In severe cases, it can lead to insufficient filling modulus of the melt, resulting in defects such as billet gaps, bottom leakage, and insufficient threads, reducing the quality and strength of the plastic parts; Properly increasing the injection pressure can improve the fluidity and viscosity of the melt, accelerate the filling speed, enhance the fusion strength of the billet, and make the billet more compact. However, if the injection pressure is too high, it can cause the core rod of the billet to deviate, resulting in burrs and increasing the molding steps.
- Inflation Pressure. To expand the blank into a container in the blow molding mold, a certain amount of compressed air needs to be introduced, and this pressure is called the blowing pressure. When compressed air is injected into the billet, its pressure is controllable, and the level of inflation pressure can directly affect the inflation molding of the billet. If the pressure is too low, it cannot make the product closely adhere to the mold cavity, resulting in unclear text and patterns on the surface of the product, which reduces its aesthetics; At the same time, it will also reduce the cooling efficiency of the product; Excessive pressure will blow through the billet. The main factors affecting the inflation pressure are the temperature of the billet and mold, the variety and performance of plastic used, the wall thickness of the billet, product size, and the inflation ratio of the billet.
- Maintaining Pressure. After the melt is injected into the mold, especially for plastic raw materials with high shrinkage rates, the injection machine still needs to maintain sufficient pressure to obtain a billet with both aesthetics and quality strength.
Adjustment of Wall Thickness Parameters for Blow Molding Billets
When blow moulding suppliers carry out blow molding, the wall thickness of the blank should be adjusted according to the blow molding method and the type of blow molding product. Taking stretch blow molding as an example, the reasons and methods for adjusting the wall thickness parameters are introduced below.
- If a manufacturer wants to stretch and blow from a high-quality container, in addition to considering the molding process conditions and mechanical equipment, they also need to consider whether the geometric structure of the blank is reasonable. For example, a transparent container must have a transparent billet. If the thickness of the billet is large and the pre-molding cooling is slow, local crystallization will occur, causing a decrease in the transparency of the billet. For billets with a certain wall thickness, the temperature when injecting molten material into the mold cavity can reach over 200 ℃. At this time, the blow moulding suppliers need to use rapid cooling to carry out shaping treatment in a very short period. Due to the thickness of the billet, its surface has formed a transparent contact cavity, but the cooling of the inner layer is relatively slow, increasing crystallinity and affecting transparency.
- The thermal conductivity of the billet, heating system, crystal structure of plastic, production capacity, and equipment used for blow molding all have a significant impact on the thickness of the billet. The cooled billet is reheated in the heating system, and the heat from the heater can be transmitted to the outer surface of the billet, which then permeates towards the inner surface of the billet. Therefore, the efficiency of heating the billet needs to be jointly controlled by two parameters: thermal diffusion rate and billet thickness. When the thermal diffusion rate decreases or the billet becomes thicker, it can cause uneven temperature distribution in the transverse direction of the billet. Due to the temperature difference between the inner and outer surfaces of the billet, the stretching ratio may be inconsistent, resulting in the appearance of bead marks on the inner surface of the container.
- To better control the heating degree of the billet, the far-infrared heating method can be used. For example, in two-step molding, using the Calrod heating system, the maximum thickness of the billet can reach 4.2mm. With the development of new heating device technology, the thickness of the billet can be further increased.
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