Electric Motion Control for Plastics

Two Rexroth experts, Neal Gigliotti , manager of Plastics Machinery Group and Paul Stavrou , manager of system applications, wrote an article for Plastics Technology on choosing the right drive.

In plastics in the early 20th century, hydraulic pumps were the method of choice for driving motors powering extrusion machines. Later, the pumps powered electric motors, but in the late 20th century it became clear that electric servo drives offer some real advantages:

• *Low noise
• *High speed
• *No leaks
• *Dynamic speed changes
• *Greater precision

The old style was able to put more sheer power behind the machinery, but now multiple drives and servo motors can be linked, and electric motion control is more energy efficient than it used to be.

Electric servo drives, controls, and motors may have a greater initial cost than some other types of motion control used in the plastics industry, but the long-term cost is lower.

One reason for this is simply the cost of energy. Maximum power is no longer the only factor to consider, given the cost of energy and also the pressure from consumers and regulations to move toward a more sustainable method. Energy savings vary from one facility to another, but experts estimate that 30-35% energy savings are possible with the use of servos.

Electric servos also have a long lifespan, and trouble shooting is likely to be easier. These factors mean that maintenance is often less of an issue.

One of the unintended consequences of that long, trouble-free lifespan is that the engineer who first has to cope with a failure may be younger than the servo he or she is trying to repair. Chances are good that none of your team has ever seen one of these babies before it stops working, so they have no experience in dealing with this type of machinery.

Give us a call. We’re specialists, and we can provide phone service, field service, and factory repair for your legacy Rexroth components as well as the newer ones.