v 2.0 — March 2023 Altanium Delta5
92 PID Control
7.10 PID Control
The sections that follow give typical PID values and possible causes of oscillation.
7.10.1 Typical PID Values
A list of some typical PID values is given in Table 7-20.
7.10.2 Possible Causes of Oscillation
It is possible to set the control terms incorrectly, which could cause an oscillation. Table 7-21
gives the most common causes.
Table 7-20 PID Values
Proportional Integral Derivative Type Example
015 010 002 Fast Probes or heaters with internally located
thermocouples
050 020 000 Fast
020 010 000 Fast
015 015 000 Fast
020 007 100 Medium Probes or heaters with internally located
thermocouples (larger mass)
020 005 200 Medium
100 003 000 Slow Manifolds or heaters with externally located
thermocouples
075 003 150 Slow
Table 7-21 Possible Causes of Oscillation
Cause Description
"P" too large Power change is too great with the degrees of temperature change.
"I" too large Power changes too quickly for the process to follow it.
"D" too large Stepped power change too large for the rate of change of temperature.
Shear An important issue often overlooked is the effect of shear in the material as
it passes through the gating area. This can cause an increase in temperature
in excess of 33 °C (60 °F) under severe conditions. Thus, if large
temperature variations occur during molding, it is worth plotting this
variation against the molding cycle time. As the controller cannot start
additional cooling, it is only possible to minimize this effect with correct PID
term selections.
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