Chapter 2 – Using Cascade Control
TestEquity F4T Controller Page 7
Chapter 2 – Using Cascade Control
Overview
Cascade Control is the technical
name for a multi-loop control
system where the air temperature
set point (Inner Loop) is
determined by deviation of the
part temperature (Outer Loop)
from its set point. The graph
shown here represents Air
Temperature vs. Part Temperature
when Cascade Control is used.
The Air Temperature is allowed to
overshoot or under shoot as
required in order to achieve the
desired Part Temperature while
minimizing lag time.
The controller is configured at the factory to allow the Air Temperature to deviate no more than
+15°C or –15°C from the Part Temperature set point. This means if the set point is 85°C, the Air
Temperature could go as high as 100°C if the Part Temperature lagged sufficiently during a heat
up condition. In the example shown here, the Air Temperature went as high as 90.7°C when the
Product Temperature achieved 83.0°C. Conversely, the Air Temperature went as low as 18.6°C
when the Product Temperature achieved 23.4°C in order to reach a 23.0°C set point. In both
instances, The Air Temperature then began to approach the Part Temperature as the part began to
stabilize, until the two temperatures were ultimately nearly identical.
Without Cascade Control the Part Temperature will take longer to stabilize due to its thermal
mass as shown in the graphs below.
Air Temperature vs. Part Temperature without Cascade Control
Part Temperature’s approach to set point with and without
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