According to Barudan project manager Wayne Rhine, the company originally installed in its single head embroiderers a linear ball bearing for motion along one axis of a two-axis pantograph. The pantograph holds a hoop that contains the fabric, Rhine said. Although the ball bearings kept friction down, they vibrated the pantograph. As a result, the machine would drop a stitch intermittently. Some customers complained of noise.

Such quality-control problems sent Barudan engineers off exploring. With a switch to polymer bearings, Rhine said, vibration stopped but so did the machine. Friction, though not a problem before, became one with the change to polymer bearings. The company tried a number of competing brands to no avail.

It was a polymer bearing from Igus that eventually solved things. What was different about this particular bearing? According to product manager Scot MacGillivray, Igus uses a ribbed design to connect glide pads with thin webs. Other competing designs do not relieve the material between the bearing surfaces in a like manner. The Igus bearings are thus less constricted by thermal expansion than other polymer designs. So, the Igus bearings can run with tighter clearances.

Another benefit, said Igus's technical salesman, Aubrey Butler, is that polymer bearings actually run better along shafts that are slightly rougher, with surface finishes of 8 to 16 microinches, than the polished shafts used for steel linear ball bearings. That, he said, has allowed the introduction of extruded aluminum shafts, which are both lighter and more corrosion resistant than their steel counterparts.

Alternating layers of metal and elastomer in this main rotor bearing ready it for battle with motions and forces from all corners.

A main rotor blade subjects its bearing to many forces and motions, explained Ernest Gaudette, a Chicago Rawhide sales manager. Centrifugal force, the largest load, compresses the bearing, which resides between the rotor hub and blade. A blade's changing pitch, as it makes its way full circle, imparts torsional rotation to the bearing. Rotor flap and lead/lag motion create angular rotation. And rotor thrust generates a radial load.

To contend with these forces and motions acting at once, designers at Chicago Rawhide develop a bearing from a number of different geometries, Gaudette said, mainly using spherical, conical, and flat shapes. By varying the number of elastomeric layers, and the stiffness of the elastomer used in each layer, the designers suit each bearing to its particular application.

This technology, proven in such aircraft as the Sikorsky UH-60 Blackhawk, replaces what might normally be a collection of distinct components with a single bonded assembly that requires no lubricant. Chicago Rawhide is searching for applications outside of aerospace where such bearings could solve other load and motion-attenuation problems. Gaudette said the company is talking with various transit authorities about the possibility of using these bearings for railcar suspension. The company is also looking at off-highway construction vehicles whose complex suspensions today require frequent lubrication.

Two-stroke bus diesels in search of lower particulate emissions mandated by the EPA will find answers in a rebuild kit from Johnson Matthey.

The new camshafts reduce exhaust scavenging by opening the exhaust valves later in the combustion cycle and closing them earlier, according to Johnson Matthey diesel engine specialist Ray Conway. Exhaust gases are thereby trapped and burned during combustion, he said. The trapped exhaust gases lower the overall combustion temperature, keeping NO_x emissions below certified limits.

A replacement turbocharger delivers extra air to lower the amount of particulate matter produced. And by exploiting the relationship between NO_x and particulate matter—where lowering one raises the other—the cam converter kit advances fuel injector timing to decrease particulate matter while holding NO_x output below the regulated limit. A catalytic exhaust muffler, which bolts in place of the original equipment, uses a diesel oxidation catalyst to finish bringing particulate matter within the EPA's mandated levels.

The Southeastern Pennsylvania Transportation Authority is one of several transit agencies that is using the Johnson Matthey cam kits to retrofit its bus fleet. Jim Hathaway, chief automotive officer for the Philadelphia-based transit authority, said that the 75-plus buses his agency has modified to date have been "easy, basically drop-in" procedures. SEPTA is meeting the EPA guideline without disturbing fuel economy or power, he said.

A typical high-speed bottling line may need to apply labels near rates of 1,000 a minute, explained API Controls' president, Greg Woods. Aligning and adhering pressure-sensitive labels to the sides of bottles shuttling randomly along a conveyor, takes a motion control system that can exactly match the speed of the labels with the speed of the bottles.

API takes a position-based approach, Woods said. Rather than assuming that the bottling conveyor moves at a constant speed, and applying a label after an interval of time calculated from that assumption, API monitors conveyor position with an encoder. Even when the conveyor speeds up or slows down in response to load, demand, or product, the encoder transmits accurate position data to the drive. Meanwhile, other sensors determine bottle presence and label position on the unwind. These data are sent to the drive as well.

Using a macro that API calls "turbo phase adjust," the drive first synchronizes the labeler with the conveyor, then compares the known position of the label against the tracked position of the product. The drive ticks off a number of pulses, then accelerates the dispenser up to speed. By varying the number of pulses that the dispenser waits before accelerating, the drive positions the label precisely on the bottle. After the sensor sees the end of the label, it counts off a second set of pulses before decelerating the dispenser.

The phase adjust registration command can compare the detected position of the label with the expected position, then initiate motion, in 100 microseconds.

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