Page 90 - Injection Molding Advanced Troubleshooting Guide
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74 8 Machine Performance
A machine can also have issues with the ability of the valve to respond as the
machine transfers from velocity control to pressure control. Tuning issues for
the valve can impact the ability of the machine to react. There will be cases
where the back pages of the machine controller must have adjustments made to
ensure that the valve is responding adequately.
Figure 8.13 Poor velocity to pressure response machine control screen; notice the dip and
spike in pressure.
This issue is not isolated to just hydraulic response. Electric presses will have a
velocity setting for the second stage that will also have a significant impact on the
process (see Figure 8.14). This RJG eDART screen shows the machine pressure,
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velocity and cavity pressure for three cycles. The three different sets of curves are
for three different set hold velocities. Note that on this process transfer actually
occurs at the bottom of the machine pressure curve not at the peak point.
