Integrated Motion Control
Applications
Electronic Cam and Mechanical Cam with Ultra5000 Intelligent Positioning Drive
As the power of electronic motion control systems has increased, the ability to duplicate the functions of mechanical cams has become possible. One of the fundamental drawbacks of mechanical cam systems is that once the cam has been created (machined); and later the user desires to modify the cam profile, a new cam must be created. This is particularly a problem in prototype mechanisms where cam profiles are determined experimentally. The ability to replace mechanical cams with programmable electronic systems allows designers to build machines that change cam profiles quickly. Different profiles stored in the controllerÕs memory can be selected to optimize the operation of the machine or accommodate different product types. Furthermore, as engineers become more familiar with the capabilities of electronic cam in motion controllers, new machine designs are possible that previously were not feasible.
Replacing a Cam and Lifter System with an Electronic Cam System
An easy way to begin to understand the operation of electronic cam systems is to replace the cam and lifter system with an electronic cam system. The electronic system detects the rotation of the original motor using an incremental encoder. The shape of the mechanical cam is effectively stored in the memory of the Ultra5000 motion controller. The motion controller then commands the servo motor to move in relation to the original motor in a manner that duplicates the action of the mechanical cam and lifter. The ballscrew actuator and servo motor replace the lifter.
Since the motion controller can store several different cam profiles, the cam-lifter relationship can be changed simply by loading a new motion program. An interesting benefit of the electronic cam system in this application is the ability to attain faster cycle rates. If we imagine that the motor in mechanical cam systems is rotating at a high speed, the lifter will eventually get thrown away from the cam surface and position accuracy will be lost. This is not a problem in the electronic cam system.