Future Design MCT-CM, User Manual

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MCT-CM
102
NOTE: Delta control is only active during the wait condition of the step. Once the wait conditions have been
met, delta control will be terminated. The loop(s) selected for delta control will then use the set point
programmed in the step. Therefore, you must make sure you program the loop set point(s) of the
step properly to maintain proper control of the process once the wait condition is met and delta control
is no longer active.
Example:
During manufacturing, a large, steel roller must be tempered in an oven after the hardening process is complete.
If heated unevenly or too quickly, the roller could warp. In order to evenly temper the roller, four thermocouple
monitor inputs of MCT are placed eve
nly across the length of the roller’s surface. This allows the operator to
monitor the temperature of the roller from one end to the other to insure it is being heated and cooled evenly.
The program must heat the roller to 400 degrees and then hold that temperature for an hour to ensure that the
core of the roller is up to temperature. After the one hour long soak at 400 degrees, the oven temperature is
lowered down to 100 degrees to complete the tempering process. In order to ensure even heating and cooling,
the program must limit the maximum temperature difference between the roller and the air temperature within
the oven to 50 degrees. If the air temperature rises or falls too quickly, or a temperature gradient between any
two points on the roller exceeds 50 degrees, it could cause the roller to warp.
In order to maintain this 50 degree difference, delta control is used to control the set point of loop 1, the oven
temperature. A Delta SP of 50 is entered and monitor inputs 1
– 4 are selected as the “wait” inputs, which are
the thermocouples placed on the roller’s surface. By using these temperature inputs, the delta control function
can add the 50 degree set point to the lowest monitor input for the heating step and subtract it from the highest
monitor input for the cooling step. The resulting value is then automatically used as the set point for loop 1.
Step 1 Loop 1 set point = 400
Time = 0
Wait Type (Increase) = monitor inputs 1, 2, 3, 4 selected
Wait set point = 400
Delta Loop = loop 1
Delta SP = 50
When the program is started, it will enter the wait condition and wait for each of the four monitor
inputs to rise to 400 degrees. During the wait condition, the Delta SP will be added to the lowest
monitor point and the result will be set to loop 1 set point. Once the wait condition is met, the delta
control function will be turned off and loop 1 set point will become the program specified set point,
i.e., 400 degrees as set for the step.