1. Pressure switch means that the priority of the machine is pressure. When the machine detects that the pressure at the moment of injection reaches the V / P switching pressure set by you, the injection action will be switched to the pressure maintaining action until the pressure maintaining is completed.
Because this method is based on stable and reliable pressure absolute value signal, this switching is the most effective. Because the influence of screw stroke and check valve is eliminated by using pressure monitoring, this method can not compensate the change of hydraulic oil, melt and mold temperature, that is, the change of injection rate.
The faster the pressure increases in the compression stage, the more effective this method is, because in this case, accurate and timely switching avoids the generation of pressure peaks. When the pressure is switched, because the minimum detection data of pressure can reach 1kgf, it is sensitive to the pressure accuracy, so it is suitable for making small precision parts.
2. The position switching (or stroke switching) is different. When the screw injection action reaches the V / P switching position set by you, the injection action will be directly converted to the pressure maintaining action.
This method is the most commonly used method and has been proved to be effective in practice. The switching signal is sent out by the limit switch at the pressure maintaining position. Since the injection stroke is basically constant, it can be considered that the switching occurs once when the same volume is filled.
If the pressure maintaining travel is very short, this method is very unreliable, because a small change will cause the switch to fail to start accurately every time. In this case, it is better not to switch. Since the switching pressure is not considered in the position switching, the maximum injection pressure should be as loose as possible.
3. The method of time switching requires that a switching signal be released after a predetermined time after the injection, and the pressure will be changed when the time is up.
This method does not consider the change of melt compression, melt viscosity, feeding accuracy or hydraulic pressure at the front end of the screw, nor does it consider the change of screw advance rate. The change of hydraulic pressure will cause the change of screw position (the end of feeding stage and the beginning of pressure maintaining stage) and the corresponding stroke change (feeding stroke and injection stroke), and the product quality is special The weight and size of the parts fluctuate greatly.
Suitable for making some ordinary products with low requirements. Therefore, time-based switching is not recommended.
