Rockwell Automation 1398-PDM-xxx IQ Master Version 3.2.4 for IA-2000 and IQ-5000 Positioning Drive Modules, IQ-55 - Manual (Page 403)

Application Examples • Thermoformer Application 381
Publication 1398-PM601A-EN-P — October 2000
APPENDIXES
Thermoformer Application
Description
Thermoformers are used in many applications where plastic sheet material is formed into shapes to
make a product or package. The basic operation of a thermoformer requires the plastic sheet to feed into
the machine where it is heated and formed, and then indexed again to a cutter which cuts out the formed
part. An Allen-Bradley motion controller drives the sticker chains which pull the plastic material
through the machine. An interface terminal allows the machine operator to easily change the move dis-
tance, dwell, speed, and other variables.
Advantages of Servo System
•
The operator interface capability of the controller allows quick set-up and change-over between
different product lengths.
• Advanced microprocessor control produces maximum accuracy and speed.
• Programmable motion controller provides a flexible system for future enhancements.
Design Considerations
Mechanics
The servo motor should be chosen based on the torque and speed required plus the reflected inertia of
the mechanics. Gear reduction through belts and pulleys or a gearbox can help reduce the system inertia
reflected to the motor. If a gearbox is used, a low backlash type, such as a planetary technology, should
be specified to maintain accuracy. If timing belts and pulleys are used, HTD tooth profile belts are rec-
ommended. Except for the main sticker chains, timing belts are recommended because belts provide
higher stiffness and less stretch.
Thermal Management
Thermal management within the thermoformer has a significant effect on the performance of the
machine. Even cooling of the plastic material is critical to maintain consistent accuracy. Uneven cooling
can create stresses that will pull the material out of position as it shrinks, and requires high torques to
overcome the additional friction.
Accuracy
The accuracy of the system is determined by the mechanics of the system and the performance of the
position control. To achieve a given accuracy, the resolution of the position feedback should be at least
five times better than the desired accuracy. The tuning of the position and velocity control loops also
affects the accuracy of the system, as well as the settling time for the system to be in position after a
move.
Interfacing
The ULTRA Plus or IQ controller provides great flexibility as a programmable motion controller for
interfacing to the machine. The program illustrated in this application note provides an output which
turns on to indicate that the material is in position and the forming or cutting operation can begin. A
ready input indicates that the operation is complete and the controller can begin the next move. Another
output is provided which can be set to turn on before the move is complete and can be used to initiate an
action, such as a preheat, prior to the material being in position.