Facing challenges

Variable velocity profiles incorporate multiple dwells, making it possible to adjust product gaps onthefly. As with trapezoidal commands, the addition of S-curving (though not shown) removes abrupt velocity changes, treating products and machinery more gently.

One challenge when designing a sorting system is knowing how to select the appropriate technology for each subsystem. Depending on the required speeds, the technologies may run the gamut from ac induction motors to steppers and servos to mechanical devices such as clutch/brakes to pneumatic cylinders. The increasing use of servos for sorting operations reflects the upward trend in system speed as well as the desire to create "all electric" systems, eliminating the need for shop air and other ancillaries.

Another challenge is having to manage several products on a sorting line, requiring different speeds and motion profiles. In many cases, sorting machines are asked to manage these changing products on-the-fly. This makes electrically based servo and stepper systems preferable because they can be configured to make changes quickly and automatically. Information from sensors out on the sorting line can identify the product, telling the motion controller how to operate the servo amplifier and motor.

Sorting system designers also are tasked with optimizing performance, for example, maximizing the speed for a given product while handling it properly. This requires selecting and implementing the appropriate motion profiles for each subsystem and each product to be handled.

Making a difference

Replacing mechanical or pneumatic diverters with servo-controlled diverters is one way to increase speed and throughput. It also eliminates the need for shop air (pneumatics) and offers greater flexibility in operation, including on-the-fly response to changing product makeup.

Induct subsystems can also benefit from smoother operation, through the use of sophisticated motion profiles (like Scurving), while maximizing system speed and maintaining accurate product placement. Not only do products move better, but the machine mechanics see less stress which boosts overall system reliability.