Gas-assisted injection molding and water-assisted injection molding are based on similar process technologies, so the scope of application is similar. So, what is the difference between the two technologies? What is the scope of application of each of these two technologies? As a very mature technology, gas-assisted injection molding has been used in the plastics processing industry for many years. One of the most important applications of this technology is the production of thick-walled plastic parts, such as production handles and similar products. Plate-shaped parts or other plastic parts with locally thickened areas are also important applications for gas-assisted injection molding. The corresponding water-assisted injection molding technology is a new technology. From the German Plastics Processing Research Institute (IKV), the preliminary results of water-assisted injection molding technology have only been published for six years. However, this technology has been developing rapidly. With. Soon after the invention of water-assisted injection molding technology, it was convenient to use this technology to process a supermarket trolley accessory. After that, people used water-assisted injection molding to mass-produce handles and rod-shaped plastic parts with large cross-sectional areas. From the point of view of actual production, plastic parts with functional space or flow path are beginning to use water-assisted injection molding technology more and more. Battenfeld developed a combined water-assisted injection molding production system based on basic research completed by IKV and its experience in gas-assisted injection molding technology. The production system consists of a pressure generator, a pressure control module and a control unit. At the same time, special syringe assemblies adapted to specific requirements have also been developed. Battenfeld has two products under the trade name "airmold" (gas-assisted injection molding) and "aquamold" (water-assisted injection molding). Comparative advantage of water and nitrogen Gas-assisted injection molding technology is used to reduce part weight and cycle time when producing rod-type components. Gas-assisted injection molding also helps to greatly reduce or completely eliminate the wall thickness area, deformation and shrinkage marks of the flat plastic parts, thereby improving the quality of the plastic parts. The thermal conductivity of water is about 40 times that of nitrogen, and the heat capacity is 4 times that of nitrogen. In addition to the normal mold cooling, water injection can cause "internal cooling" of the plastic parts. Compared with the gas, the cooling time is shortened by 70%, and the plastic parts reach the required demoulding temperature much faster. At the same time, water is also an incompressible and inexpensive medium. Replacing nitrogen with water will result in better surface quality of the cavity. In addition to being able to machine larger parts, water-assisted injection creates a more uniform wall thickness and reduces residual wall thickness. Water-assisted injection molding and gas-assisted injection molding can be used in different processes. They do not differ in the use of the machine, but there are differences in mold design and process control. Water-assisted injection molding is a two-step process similar to gas-assisted injection molding: first, the cavity portion is completely filled with the melt; in the second step, the injected water forms a cavity. Features of water-assisted injection molding equipment Water-assisted injection molding equipment must be designed to meet similar conditions to gas-assisted injection molding. This is because most process technologies are based on gas-assisted injection molding. However, water-assisted injection molding also has its own characteristics. From the perspective of plastic parts, in addition to drainage is more complicated than the removal of nitrogen, it is necessary to complete the "drainage" of the plastic parts by gravity and by introducing compressed gas. To prevent corrosion, the water must not come into contact with the mold surface. Water-assisted injection requires extremely high water injection capacity to ensure uniform wall thickness distribution and high surface quality. To this end, Battenfeld developed a suitable pressure control mode. The water supply operates at very high flow rates and can reach pressures of 350 bar. In order to inject water into the melt, it is necessary to utilize an injection assembly having a larger cross-sectional area than gas-assisted injection, which is essential for the penetration of water into the melt at a sufficient rate. Battenfeld's water-assisted injection pressure generation device is designed as a stand-alone unit that provides pressure to multiple injection molding machines simultaneously. The water pressure control components are controlled by the Unilog B4 mobile control unit. In general, they can also be used on machines from other manufacturers. Economic comparison between gas-assisted and water-assisted In order to make the right decision on the economic production of plastic parts, Battenfeld collaborated with Cologne University of Technology to compare the following five processes using experimental molds: Traditional injection molding Short shot gas injection molding Full injection gas-assisted injection Short shot water auxiliary injection Full injection water auxiliary injection In order to achieve meaningful results, it is necessary to utilize materials that are easy to handle in all processes. However, raw material manufacturers are just beginning to optimize materials for water-assisted injection molding. When plastic processing is performed by water-assisted injection molding, some materials are liable to form foams, shrinkage cavities or side grooves. In addition, there are some materials that can cause cracking, blistering and non-reproducible properties due to water. In some fiberglass filled materials, the glass fibers may be washed away, resulting in a rough inner surface. Therefore, the following three materials were selected for this experiment: Bayer's Pa66 Durethan BKV30GH DuPont's PBT Crastin T803 DSM's PP. The plastic parts are machined on the BattenfeldTM 4500/2800 Unilog B4 injection molding machine. The press has a clamping force of 4500kN and is equipped with an interface for gas-assisted and water-assisted injection molding. Water-assisted injection molds are generally more expensive than gas-assisted molds because of the different steels used to make the molds. The quality of the steel used in the water-assisted injection mold is higher (a strong nickel-plated or titanium nitride coating is essential to protect the water-assisted injection mold from corrosion). The experiment assumes that the operation time is 24 hours per day, the working day is 300 days, and the system utilization rate is 90%. The depreciation period is assumed to be 8 years. Variable costs, such as labor, energy and other costs (cooling water, cleaning costs, etc.) are included in this calculation. In water-assisted injection molding, the cost of water is also included. The cost of nitrogen formation is taken into account in procurement and energy costs. The procurement cost of gas-assisted and water-assisted injection molding is 100,000 to 145,000 euros higher than that of solid plastic injection. In the short injection process, the procurement cost of gas-assisted injection molding is much lower than that of water-assisted injection molding, which means that the critical production capacity of the gas-assisted injection molding process is 5000±500 units lower than the critical production capacity of the water-assisted injection molding process. In special times, for example for test parts of polyamide materials, the critical production capacity of gas-assisted injection molding is 38,206 units, and the water-assisted injection molding is 43,203 units. The calculations are based on component weights and cycle times obtained in a series of tests for various materials. The weight of the polyamide plastic part as a solid injection molded part is 224g, the gas-assisted injection molded part is 114g, and the water-assisted injection molded part is only 104g. The number of critical plastic parts depends on the process and materials In a direct comparison of gas-assisted and water-assisted injection molding, after less than 65,000 production volumes, short-shot water-assisted injection molding brought profit to the Pa test plastic parts. In this process, material prices play an important role in the absolute number of critical production. For the cheapest PP in the material to be tested, the critical production capacity of water-assisted injection molding and solid plastic injection molding is 75,000. In the full injection process, the cost situation is different. For all three materials, the production cost of plastic parts for water-assisted injection molding is below the cost of gas-assisted injection molded parts. One of the main reasons is that the use of full injection gas-assisted injection molding requires a license fee. Due to the higher production capacity, the variable cost of water-assisted injection molding is lower than that of gas-assisted injection molding. It has been found through experiments that the critical throughput of the full injection process is much higher than the critical throughput of the short injection process. High procurement costs mean that material prices have little to do with the cost of plastic parts. Water-assisted injection molding technology is an ideal complement to gas-assisted injection molding technology. The advantages of water-assisted injection molding include better distribution of residual wall thickness, more uniformity, and shorter cooling time. From an economic point of view, the water-assisted injection molding process is cheaper than gas-assisted injection molding because it does not involve license fees. If a short shot process is utilized, the more economical process is entirely determined by throughput and materials. Of course, to take full advantage of this advantage, more information on the factors affecting the process must be collected. For the special requirements of water-assisted injection molding, raw material manufacturers also need to adjust their product grades. Lever Block,Lever Chain Hoist,Ratchet Lever Hoist,Ratchet Hoist Guangdong Gongyou Lift Slings Machinery CO.,LTD , https://www.workmateslift.com