Interpretation of Injection Pressure Velocity Curve

Time:2022-08-04 08:57:55 / Popularity: / Source:

Injection curve is an indicator light in injection molding process. Combining injection curve during process debugging can improve efficiency, reduce debugging waste and reduce debugging cost.
From pressure-speed curve, we can see actual pressure and speed changes, pressure-speed state when pressure is switched, matching of pressure and speed, so as to assist debugging and scientifically set process.
Injection pressure setting is maximum allowable injection pressure during injection.

Injection pressure setting

Example 1:
Injection Pressure Velocity Curve 
As can be seen from figure, right horizontal axis where curve is located is screw position, left horizontal axis is holding time, right vertical axis is speed scale, left vertical axis is pressure scale, and curve is viewed from right to left.
Red speed line of curve is a sharp peak, speed rises sharply and then falls sharply, and filling is fast. Because there is no holding pressure, tail end has a rebound. Yellow pressure curve increases with speed and plateaus after a peak.
Opening position of injection pressure control valve at peak of injection pressure to ensure that injection pressure is not higher than set value. After pressure control valve is opened, pressure is maximum value and curve tends to be stable. A sudden drop in pressure indicates that injection time has been reached.
Example 2
Injection Pressure Velocity Curve 
This curve is curve change process after gradually increasing pressure. Increasing pressure has a significant effect on second half of injection process, and injection volume continues to increase. This is due to pressure settings that are too small (premature spikes).

Pressure holding switch position selection

Example 3
Injection Pressure Velocity Curve 
It can be seen from this curve that after injection speed is reduced to 0, injection process continues for 2s. This is because injection has reached end point and injection time is set too long. It is suggested that injection time should be about 0.8s according to complete condition of product, so that pressure curve does not appear sharp peaks as much as possible, long injection time is replaced by holding pressure to prevent product from being overfilled and stress is too large.

Pressure and speed adjustment

Working pressure during injection process depends on resistance, and speed is one of factors that determine working pressure. Injection pressure is set according to injection speed, so that speed can reach set value without being too large. It is recommended not to exceed 10% of maximum injection pressure.
Example 4
Injection Pressure Velocity Curve 
To make injection speed stable, it is necessary to set enough injection pressure by increasing injection pressure so that curve does not have a peak before it stabilizes. When setting multiple speeds, actual speed at speed switching position can be seen from curve, and speed or position can be adjusted as needed.
Example 5
Injection Pressure Velocity Curve 
It can be seen from figure that there is no pressure peak in process, injection speed is stable, injection pressure is set reasonably, injection speed is small at beginning of pressure holding, pressure holding can be switched accurately, and position is reasonable.
Making good use of pressure-speed curve is an important method to improve debugging efficiency and optimize process.

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