Leadscrews: Not just economical
New leadscrews are more than an economical ballscrew alternative. New materials are boosting their efficiency.
| Particle Emission Rates |
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| Mechanism | Test Velocity (RPM) | Emission Rate (Particles Per Min.) |
| Stepping Motors DC Brush Motors Shielded Ball Bearings Linear Bearing Linear Leadscrew Ballscrew Spricket and Poly Chain |
900-1,200 3,000-7,500 600-1,200 150-1,200 50 ft/min @ 1,200 50 ft/min @ 1,200 600-1,200 |
0-1,000 0-30,000 0-4,000 300-10,000 20-100 2,000-3,000 4-300 |
Low cost ball screws often have imperfect thread forms that cause the ball to skid rather than roll. This behavior leads to accelerated wear. The smooth motion (and no impacting) of leadscrews means they actually generate less particulate than other wear components. |
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Saving a bundleOmega Design Corp., Exton, Pa., manufactures packaging equipment systems — plastic bottle and puck unscramblers, shrink bundlers, stretchbanders, and orienters. One of the company's products (the Classic Series of shrink bundlers) is in worldwide operation. This pneumatically-driven, PLC-controlled machine was designed for automatic shrink packaging of containers into predetermined bundle configurations. It helps eliminate the cost of cardboard boxes and creates a more secure package, which lends itself to further automation down the line, such as case packing. With unique packaging on the rise, Omega needed to accommodate alternative package configurations. After incorporating several changes, the company focused on the product pusher, a pneumatic-driven actuator that pushed product into film or other packaging material. Inherent to pneumatic actuators is play and uneven motion control, causing inconsistent product flow through the pusher area, misaligned products, and machine stoppage. Air compression is also expensive. After discussions with applications engineers, Omega decided to replace the pneumatic pusher with a high-speed Kerk RGS (Rapid Guide Screw) 10000, a cost-effective, screw-driven slide. Omega's engineers then worked with Kerk to incorporate a servomotor and a few additional components to create an intelligent motion system. "It was a simple swap-out," says Devendra Shendge, a product development specialist with Omega Design. "The slide was retrofitted to the unit we were using and easily met the space constraints." Speeds over 60 in./sec are possible, rivaling belts and cables while maintaining axial stiffness. The screw generates 150 lbf, while the original air cylinder only produced 80 lbf. Also: "Before it was just a continuous motion, 0-50 in./sec," says Shendge. "Now we can accelerate or decelerate the machine. This is critical, because when you're dealing with unusual shapes and heavier mass, you can't just thrust them through the machine at top speed. You can damage the machine as well as the product." Omega first put the new Classic shrinkbundler on exhibit at the PMMI Pack Expo Show in Las Vegas, 2005. |
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© 2012 Penton Media Inc.
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