1, injection oil road
Injection and back pressure adjustment oil circuit diagram Solution: The injection oil circuit is closed by improving the oil circuit, and the injection oil hole is not connected to the oil return hole. In this way, the injection cylinder piston is locked, and the injection component is protected from the inertia caused by the movement of the switch mold (the injection screw does not generate relative motion with the component), the injection amount can be precisely controlled, and the nozzle flow can be effectively reduced.
2, pre-plastic feeding and pumping loose
When the oil motor drives the screw to rotate, the heat-softened plastic material is pushed forward and passes through the check ring to reach the front end of the screw. As the screw rotates continuously, the front end of the screw is more and more melted. In this area (measuring chamber), pressure is generated and acts on the screw and the check ring, pushing them up to allow more space to accommodate more melting. material. In order to prevent the screw from rising too fast and to ensure uniform compaction of the melt, it is necessary to provide a reverse pressure to the screw. When the screw rises, the injection cylinder piston is lifted, and the injection chamber hydraulic oil flows back to the oil tank. By controlling the pressure of these hydraulic oil backflows in a certain way, it is possible to control the resistance of the screw rise. The return pressure in the injection cylinder at the time of the melt is usually referred to as the feed back pressure. The application of the back pressure of the melt can make the screw generate enough energy to melt and mix the plastic during the rotary reset, and has the effect of exhausting and enhancing the color mixing, which helps the melt to be uniformly and stably plasticized. It is one of the important parameters to control the quality of the melt and the quality of the product in the injection molding process. Suitable back pressure plays an important role in improving the quality of the product. The current vertical injection molding machine back pressure control method is to connect a one-way throttle valve in series on the oil injection line of the cylinder, as shown in the above figure. By adjusting the size of the throttle opening to control the flow rate of the injection cylinder returning oil during the melt, the back pressure of the screw rise is controlled. However, when the throttle valve is a back pressure valve, the pressure value changes with the flow rate (the back pressure control is not accurate). The back pressure is unstable, the plastic melting does not meet the requirements, and the quality of the finished product is certainly not high. At the same time, in order to prevent the nozzle from flowing easily due to the back pressure being too high, the melt plastic is overflowing from the nozzle. It is necessary to use the function of pumping back, that is, the pressure oil is introduced from the lower chamber of the injection cylinder through the cylinder. The piston pulls the screw up. However, when the lower chamber enters the oil, the oil returning from the upper chamber of the cylinder is restricted by the back pressure throttle valve, and the pumping loosening action must be performed under a large pressure (the pressure loss is large). From the perspective of energy saving, this oil circuit is also not desirable. Solution: Improve the oil circuit design and use the relief valve as the back pressure valve. Compared with the throttle valve, the relief valve can better maintain a constant back pressure and the plastic melts better. At the same time, the action of pumping loosening is not affected by the feeding back pressure valve, and the action is quick and the anti-flowing effect is better.
Dongguan Taiwang Machinery Co.,LTD
Add:NO.127,longyan road,Chongkou Industrial district,Dongguan city,China.