Tip of the Day 66: Injection Integral Depends on Injection Time

Tip # 61 showed how variation in screw run time can affect the Cycle Integral calculation. Remember that the Integral is an area and the “width” of the area is defined by the time over which the integral is computed. The eDART’s summary value of type “Injection Integral” also depends on an end time. For Injection Integral the end of integration is the end of Machine Sequence / Injection Forward.

Adjusting Hold Time Changes Injection Integral

Two scenarios have tripped up our customers recently. In the first someone may adjust the hold time from one setup to the next. Changing hold time will change the area over which the integral is computed. If alarms are set on Injection Integral then the part may be considered bad.

Notice that a change in Injection Integral may indicate a real problem. For example, if someone sets a shorter hold time then the gate may not seal causing material discharge and a change in part quality. Thus the Injection Integral alarm would pick up the change and the diverter could discard the part.