In general, the so-called ultra-high-speed injection molding has two meanings. One refers to the machine forming thin-walled products at ultra-high injection speed, and the other refers to high-speed cycle molding. In any case, the former should be a necessary condition for the latter, so in this article, Only a brief introduction is made for the purpose of ultra-high-speed injection moulding, the main characteristics and technical applications of moulding machines.
1. Purpose of Ultra-high-speed Injection Molding
Generally speaking, the injection speed below 300mm/sec is classified as a traditional injection machine.
The injection capacity of 300mm/sec~600mm/sec (800mm/sec in a word) is classified as a high-speed injection machine.
The injection capacity above 600mm/sec (or 800mm/sec) is called an ultra-high-speed injection machine.
The ultra-high-speed injection molding machine is generally used for thin parts molding. The so-called definition of thin-walled products generally means that the finished product with an L/T ratio of 150 or more, or a wall thickness of 1.0~0.8mm or less, is regarded as a thin-walled product.
No matter what kind of product, in order to achieve ultra-thin wall, we must first use the molding material with good fluidity, and make the material maintain a sufficient flow state during the filling process of the cavity. In general injection molding, during the melt filling process, affected by the cooling of the mold, a solidified layer will be formed on the contact surface of the molten glue and the mold. The solidified layer will gradually thicken as the filling time increases, thereby reducing the time when the molten glue passes through the runner. The cross-sectional area is increased, and the flow resistance and injection pressure increase, resulting in an increase in the residual stress of the finished product, and the increase in the guide caused by the flow alignment causes warpage. If the solidified layer completely obstructs any cross-section of the filling runner At this time, the melt cannot completely fill the cavity and cause short shots.
In addition, the melt flow behaviour is a non-Newtonian fluid, and its viscosity is inversely proportional to the shear rate. When the shear rate is greater, the viscosity becomes lower (this is the so-called shear-thinning characteristic). Therefore, when using ultra-high-speed injection, In addition to using ultra-high-speed to complete the filling instantly to avoid the problem of solidified layer blockage or closed flow channel, the double effect of shear-thinning and shearing reduces the viscosity of the melt, improves the fluidity of the melt, reduces the injection pressure, and achieves thin parts The purpose of molding.
2. The Required Characteristics of Ultra-high-speed Injection Molding Machines
Compared with traditional injection molding machines, high-speed injection molding machines have the following characteristics
(1) High-horsepower drive unit
The basic requirement of ultra-high-speed injection molding is to provide ultra-high injection speed and higher injection pressure. What it represents is that the injection machine needs to have high injection horsepower; but because in the entire cycle, not every action is required Such a high-pressure flow is required, so in general design, pressure accumulators are used as the power source for rubber injection to provide the large flow required instantaneously. When other actions are used, the oil volume required by the pressure accumulator is supplemented to reduce Design the required horsepower and cost, and achieve the energy-saving effect.
(2) High response hydraulic system
System dynamics are the overall performance of the electronic control system, hydraulic system and actuation system. In the selection of hydraulic components, the ultra-high-speed injection is mostly controlled by a servo valve or a proportional valve. The servo characteristic curve must indeed cover the load of the injection project. The curve must be at least 0.01sec in the servo response.
In the design of the hydraulic system, in order to achieve high responsiveness and control accuracy requirements, in addition to the small size of the hydraulic pipeline, the mass of the piston and the load should also be small, and the equivalent elastic modulus E between the hydraulic oil and the pipeline should be high. Must have Meter-in and Meter-out design.
(3) High precision and stable control system
When the high-speed injection is required to achieve high-precision control, the update capability of the servo control must be within 0.001sec. At the same time, the nonlinear characteristics of the servo valve and the flow variation caused by load variation must be compensated to achieve stability. Rate of fire control.
(4) High rigidity clamping mechanism
The rigidity and parallelism of the template body of the ultra-high-speed injection machine are required to be high, so as to avoid the production of burrs due to high-speed impact and good fluidity.
(5) Feeding mechanism with high plasticizing power
Under ultra-high-speed molding, because the injection process is very short, the overall molding cycle speed depends on the plasticizing ability of the machine. How to achieve high plasticization and high-precision plasticization effect of high-mix chain from screw design and processing is to achieve precision The key to molding.
3. Application of Ultra-high-speed Injection Molding Technology
The application of ultra-high-speed injection molding on thin parts is generally divided into three categories.
The first category is the meagre products belonging to people's livelihood products, which are characterized by meagerness, but require less precise forming dimensions, such as aviation cups, food containers, food plates, vases, etc.;
The second category is electrical machinery parts, in addition to ultra-thin characteristics, some dimensional accuracy requirements, such as intake manifolds, oil seals, bearings, oil seals, ABS pistons, pinions, horn nets, plastic filters;
The third category is electronic information products, which not only require precise molding dimensions, but also have different requirements for the mechanical, optical, and even electrical characteristics of the finished product, such as CD, DVD, non-contact IC card, optical fibre connector, connector, Reading head socket, IC slot, IC tray, clock or camera parts, etc.
4. Conclusion
With the rapid development of global 3C, optoelectronics and communication industries, short, small, light and thin have become the inevitable trend of related products in the future, and the demand for ultra-high-speed injection molding machines will also increase every year. As an excellent injection molding machine Machine manufacturers, we have produced various specifications of high-speed injection molding machines to meet customer needs. If you plan to buy a high-speed injection molding machine, you might as well take a look at the machines we provide.