A D V E R T I S E M E N T

Hypoid Gears and Gearmotors

example, gearmotors generally see intermittent use, not continuous full-load operating conditions. Yet Bison Gear has tested SRH designs that lasted more than 10,000 hours under continuous full-load, where most competing designs survived only about 4,000 to 5,000 hours. The SRH designs higher efficiency and cooler running is definitely noticeable in terms of longer life, regardless of the duty cycle.

ARE THEY MORE EXPENSIVE THAN COMPETING DESIGNS?They do carry a slight premium.

Gearmotors with hypoid gear sets are more costly than more-traditional gearmotors because they require a more-exacting manufacturing pro-cess. But compared to conventional units, a premium hypoid gearmotor will more than pay that back with anywhere from 10 to 20% greater life in normal operations, and up to double the life under the most-demanding conditions. Higher energy efficiency adds to the savings when one considers overall lifetime costs.

WHERE SHOULD HYPOID GEARMOTORS BE USED? Really, in any power-transmission

application where compact size, long life, and energy efficiency are important. In packaging machinery and conveyor systems, for instance, theyre recommended because theyre lightweight and will reduce power consumption. Other recom-mend applications include machining centers using chip augers, filters, skimmers, or chip conveyors. Users will notice a significant drop in electrical costs in many of these machines and applications.

material such as 4140 steel. The machined parts are then heat-treat-ed to increase the hardness. Typical hardness levels for gearmotor com-ponents range from 51 Rc for small-er gears to 62 Rc for larger sizes. After hardening, the gears are

then ground to the final dimensions. For SRH gears, the tolerances are extremely tight. For example, the outer diameter of the gear, inner diameter of the bore, and runout on the motor shaft are all held to tolerances of less than 0.0002 in. Finally, each tooth is ground to a highly precise profile to get almost theoretically perfect dimensions and roll patterns. The resulting gears have the same AGMA rating as precision aerospace-grade gears.

DO THEY HAVE SPECIAL LUBRICATION REQUIREMENTS?They do. Because the sliding force

between a hypoid gear and pinion might be five times greater than the forces seen in a typical cylindrical gear, these gear sets cannot rely on a general-purpose lubricant. Instead, experts recommend a synthetic grease that contains a high-pressure additive. Such a formulation will handle the contact pressure between the teeth, properly lubricate the gear set, dissipate the generated heat, and ensure that the lubricant remains grease and does not become a liquid under extreme localized pressures.

DO HYPOID GEARS PROVIDE GOOD SERVICE LIFE?Properly lubricated and used

within recommended engineering guidelines, gearmotors with hypoid gears will last a long time. For

hypoid gears generate much less heat due to friction, and experience less tooth wear. And they can pro-duce the same output power with a smaller motor, further reducing heat generation. The end result is lower gearbox temperatures that extend the life of lubricants and other com-ponents, and possibly eliminates the need for costly supplemental cooling.

ARE ALL HYPOID GEARS THE SAME?No. Gleason, the leading producer

of gear-manufacturing machine tools, has coined two terms for hypoid gears: high reduction hypoid (HRH) and super reduction hypoid (SRH) the latter being an improved version with higher efficiency. The SRH design is the latest hypoid tech-nology and is more efficient gearing than the older HRH profile, making it preferred in high-end gearmotors.

DIFFERENT MANUFACTURING PROCESSES ARE USED TO MAKE THESE GEARS? Correct. The general manufactur-

ing processes used to make HRH and SRH gears are similar, but the math behind them is a bit different. The pattern, gear geometry, and tooth geometry all differ slightly. With an SRH gear set, the pressure angle and spiral angle are adjusted to get a better mesh between the two, and the pinion and gear are both ground to reduce the sliding force, generating less friction and heat and improving efficiency. The initial step is to take a cone-

shaped blank with the basic gear geometry and cut the teeth into the gear and motor-shaft pinion. Blanks are made of a high-hardenability

COULD YOU GIVE A BRIEF OVERVIEW OF HYPOID GEARS?Hypoid gears are similar to

other spiral bevel gears in their general appearance. They have curved teeth that contact each other smoothly and gradually from one end of the tooth to the other. However, hypoid gears have axes that do not intersect.

WHAT ARE SOME ADVANTAGES OF HYPOID GEARS?The distance between the axes,

called the offset, permits higher reduction ratios than is practical with other bevel gears. The offset axes also result in meshing conditions that improve the running properties and load-carrying capacity of the gear teeth. Theyre noted for gener-ating little or no noise and vibration, even at high operating speeds. So the end result is a quieter gear set that is capable of higher loads.Among the advantages of hypoid

gears, the non-intersecting axes often result in space savings and greater design flexibility. They can be used to transmit power between shafts at most any angle and speed. Hypoid gears can also be significantly more efficient than cylindrical and worm gears.Hypoid gears are recommended in

industrial applications that demand extreme smoothness and low power consumption. For example, theyre used in high-performance gearmotors that demand high torque capacity for a given size, low backlash, and quiet operation.They also operate at higher

efficiencies than is possible with traditional right-angle gearmotors. Compared to worm-gear drives,

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