Injection curve is the indicator light in the process of injection molding. In the process of process debugging, the injection curve can improve the efficiency, reduce debugging waste and reduce debugging cost.
From the pressure speed curve, we can see the actual pressure and speed changes, the pressure and speed state during the pressure holding switch, and the matching between pressure and speed, so as to assist debugging and set up the process scientifically.
The injection pressure setting is the maximum allowable injection pressure during injection.
Injection pressure setting
Example 1:
It can be seen from the figure that the right horizontal axis of the curve is the screw position, the left horizontal axis is the pressure holding time, the right vertical axis is the speed scale, the left vertical axis is the pressure scale, and the curve is viewed from right to left.
The red speed line of the curve is sharp peak, the speed rises sharply and then drops sharply, and the filling is fast. Because there is no pressure retaining set, there is rebound at the end of the curve. The Yellow pressure curve increases with the velocity and tends to be stable after the peak value appears.
The opening position of the injection pressure control valve at the injection pressure peak value ensures that the injection pressure is not higher than the set value. After the pressure control valve is opened, the pressure is the maximum value and the curve tends to be stable. A sudden drop in pressure indicates that the injection time has been reached.
Example 2
This curve is the curve change process after increasing the pressure gradually. The effect of increasing pressure on the second half of the injection process was obvious, and the injection volume was increasing. This is due to the too small pressure setting (premature peak).
Selection of pressure maintaining switching position
Example 3
It can be seen from this curve that the injection process continued for 2 s after the injection speed was reduced to 0. This is because the injection has reached the end point and the injection time is too long. It is suggested that the injection time should be about 0.8s according to the integrity of the product, so that the pressure curve does not appear peak as far as possible, and the long injection time should be replaced by holding pressure to prevent the product from overfilling and excessive stress.
Pressure and speed adjustment
The working pressure in the injection process depends on the resistance, and speed is one of the factors determining the working pressure. The injection pressure is set according to the injection speed, so that the speed can reach the set value, and it is not easy to be too large. It is suggested that the injection pressure should not exceed 10% of the maximum injection pressure.
Example 4
In order to make the injection speed stable, enough injection pressure should be set. The method is to increase the injection pressure so that the curve does not appear peak before it is stable. When setting multi segment speed, the actual speed at the speed switching position can be seen from the curve, and the speed or position can be adjusted as required.
Example 5
It can be seen from the figure that there is no pressure peak in the process, the injection speed is stable, the injection pressure is set reasonably, the injection speed at the beginning of pressure maintaining is small, the pressure holding can be switched accurately, and the position is reasonable.
Making good use of the pressure velocity curve is an important method to improve the debugging efficiency and optimize the process.
