Integrated Motion Control
Applications
Press Feed with 1394 Motion Control System
In a typical press feed system without electronic cam capability, the servo motor drives a set of nip rolls that feed material into the press system. A position encoder on the press flywheel must monitor the location of the press mechanism (the press angle) and determine when material can be fed into the press. The system must allow operator control of the move length. To minimize wear-and-tear on the machine and improve throughput, it is desired to feed the material into the press over a fixed percent of a machine cycle using non-linear acceleration rates. When the press is running slow the feeding of the material is also slow and at high speed the feed is fast. Registration capability is also required for some materials. A high dynamic response servo is necessary for high hit rates and stiffness.
However, in every electronic motion controller, there is a delay between the point when the master encoder distance triggers the infeed motion, and when the infeed motion actually occurs. The error that can develop from this delay is significantly affected by the cycle rate of the system and the speed with which the motion controller executes each program statement. In general, the higher cycle rates produce greater errors. An easy way to correct this problem is with the use of position locked electronic cams.
Using this method, the delay to execute the infeed motion is eliminated and subtle modifications can be applied to the cam profile to optimize the motion of the infeed.
Rockwell Automation Solution
The 1394 Motion Control System with Cam and operator terminal allows a customized operator interface for a press feed machine. An electronic cam profile is used to define the position of nip rolls as a function of the press's main drive. The user program can prompt the operator for the necessary feed. The program variables make changes easy even during a run. Non-volatile variables maintain the operator data without power. The 1394 system position latch and interrupt inputs provide the fast response necessary for accurate registration, and the optically isolated I/O makes the interface simple.