Effect of precision injection molding on hydraulic cylinder
Injection molding parts with high dimensional accuracy, which can be used in precision injection parts injection pressure plastic technology in the production of hydraulic cylinder The control and adjustment system of the injection machine must ensure that the continuous processing step is the plastic, the measurement, the injection, the pressure keeping and cooling can be repeated.
The accuracy of the injection molding parts can be achieved and maintained more depends on the injection mold design and mold design and processing. Standard of judgment is whether suitable for processing plastics parts in the injection molding design and mold gate filling performance is good, the mold cooling system can uniform cooling.
Injection molding parts with residual stress must be used for injection molding. In the injection molding technology, the hydraulic cylinder successfully completed each step of the overlap. The injection machine must be fitted with a quick response of the hydraulic system, and the measuring device used in the machine must have a high accuracy.
Injection molding reduced residual stress
In addition to the size of the injection must be accurate, but also to meet other quality requirements. Therefore, optical parts must not produce residual stress. For example, the residual stress in a hydraulic cylinder lens can produce a double refraction, thus reducing the reproduction of the real. For optical carriers, this limits the density of information stored.
Injection molding parts of the production is actually not the residual stress, which is mainly to melt into the mold, the mold has been maintained a certain gap. The size of the gap varies depending on the injection, ranging from 1mm-20mm, even to 50mm. Only after the injection is complete, the mold is completely closed, and the clamping force is established. Therefore, the opening of 200 liters large iron injection pressure plastic need positive mold.
The compression process may be required at the same time as the final 1/3 of the injection cycle, according to the injection conditions and the requirement of the injection conditions. On the other hand, there are a number of cases such as the mold of the laminate decorative materials, the injection mold just open a certain distance. Until the final stage of the injection is to start the compression.
As the material is injected into the half open mold this process in a large flow channel, so the injection pressure required by the injection pressure than the traditional injection process 5-10 times. Even in the molding process of the melt agglomeration, the pressure of the mold cavity and the shear stress of the melt are also very low. Therefore, the compression molding part does not exist the residual stress.
The storage capacity of the disc is 650MB, while the low stress digital optical disc (DVD) can be used for injection compression molding, and the storage capacity of the hydraulic cylinder is 17000MB. The cause of this difference is the birefringence, and the birefringence of the injection part is much larger than that of the injection part.
In addition to the important quality criteria of the stress induced birefringence, the surface of the disc storage carrier on the pinhole structure must be able to reproduce the true. For example, the only ROM DVD required for the is only 10nm, compared to the RAM DVD, which requires a high fidelity, the required depth of the pin hole is increased to 30nm, which is because the RAM DVD contains additional information. In order to obtain such a pinhole structure, all the processing capacity must be fully utilized. This requires not only a high mold temperature, but also a high compression speed of the complex compression process.
In addition, injection and compression can also be used before the car inner decoration molding fabric decoration material or soft foam films compressed to automotive interiors. In this case, the low mold chamber pressure causes the decoration material to be unaffected by shear, stress and pressure.
Fast measurement technique for reciprocating movement
Injection compression using the same machine molding machine. In injection molding, the process sequence is completed. Because of the clear division of labor, the control system of hydraulic cylinder of the machine can be in control of every process.
In the process of injection compression, the lead time of the injection process is determined by the pressure and time. The error of these two processes must be very small. The installation procedure of the injection machine is as follows:
In order to accurately measure the position, speed and pressure, high precision and high hydraulic pressure measurement system is needed;
In order to ensure that the control system works effectively in a short injection cycle, the high speed scanning rate is required and the reading speed is converted into a parameter which can be processed;
A hydraulic system is required to adapt to the change of the parameters of the control parameters.
Compared with the traditional injection machine, the first two points do not need to increase the additional investment will be able to achieve. The screw forward and mobility template by using ultrasonic positioning measuring device is favorable, the hydraulic cylinder for control system receives the absolute value, returns the position measuring device of reading accuracy on the + 10 m.
The pressure sensor and the cavity pressure sensor of the hydraulic system should be accurate to 0.01% of the final measurement value. As for the temperature measurement, the accuracy and power of the 45MN steel plate standard sensor is enough, because the change of temperature is much slower than the parameters of the measurement.
If the measuring device is scanned at a relatively high frequency 1kHz (sampling rate 1ms), the control system is able to receive enough data to determine the existing position and the speed, and the accuracy is sufficient.
Hydraulic servo valve
For the hydraulic device, the hydraulic oil storage device must ensure that all the machines are performed independently and simultaneously. Hydraulic cylinder to reduce energy consumption and the installation of a direct electric motor driven by the screw injection machine is also true.
Another problem to be considered for the control response of different hydraulic circuits is the compressibility of oil. When the volume of the oil is large, the compressibility may cause time lag, such as the injection curve and the speed of the mold.