Gears for torque and tuning

Open gearing. Image courtesy Intech Power

Gears complement electric motors in industrial and consumer designs. For example, everything from amusement rides to consumer-grade beard trimmers make use of spur gears.

These roll through meshing for up to 98% or higher efficiency per reduction. The only caveat is that they exhibit tooth sliding and noise due to initial tooth-to-tooth contact and audible shock loads.

DieQua Corp. PGW Series reducers come in variations that are particularly suitable for belt and leadscrew-driven axes. Ratios are 3:1 to 1,000:1. Backlash is to ≤ 6 arc-min. and efficiency is to 95% or better. The PGW speed reducers are also quiet — generating operating noise that is less than or equal to 63 dB(A).

Helical gear reducers are costlier upfront than spur sets, but work in designs needing high horsepower and efficiency. Textile machinery, conveyor drives, rolling mills, and elevators all use helical gear teeth to engage gradually over the tooth faces for smooth operation and high load capacity. The only caveat is that the machine setup must include framing or supports to resolve thrust loads originating from the gears.

Non-parallel and right-angle gears go into motion applications for material handling, aerospace and defense, packaging equipment and food-processing machinery.

Consider a consumer-grade application. The Hoover Rogue 970 robot vacuum is capable of up to two hours of cleaning before recharging. Note the precision geartrain on the wall-edge brush assembly. Image courtesy HOOVER • Techtronic Industries TTI

Input and output shafts protrude in different directions; gear teeth are worm, hypoid, bevel (straight, spiral or zerol), skew or crossed-axis helical. Common bevel gearsets often go into material-handling and packaging equipment.

Hypoid gears (useful for high-toque applications) are like spiral-bevel gearsets, but output and input shaft axes don’t intersect — and that simplifies integration of supports. Common in aerospace, zerol gearsets have curved teeth that align with the shaft to minimize thrust loads.

Planetary gearing is a mainstay in myriad applications.

BEHIND THE SCENES: MAKING GEARS TO MAKE GEARS

Consider another machine-tool application. When Taiwanese company Chien Wei Precise Technology needed new CNC grinders to manufacture gears for robotics, they partnered with CNC supplier NUM. NUM’s Flexium+ 68 CNC systems on their machines let Chien Wei make both involute and cycloidal precision gears.

Chien Wei makes vertical grinders, jig grinders, machining centers, coordinate measuring machines, and now gearing for robotic automation. The latter is typically planetary gearing (with involute gears) or cycloid gearing (with a reduced-epitrochoid rotor and cycloid stator). Planetary gearboxes are an industry mainstay, but cycloid drives have fewer moving parts and are more efficient at high reduction ratios. That’s because a speed reducer with a ratio of 200:1 might need three planetary stages with 12 involute gears. 200:1 with a cycloid drive needs just a single stator-rotor pair. The catch is that cycloid gears are difficult and expensive to manufacture.

In 2015, Chien Wei brought gear manufacturing in-house for integration in its machines and for sale to machine builders. Initially its gear-grinding machine included a Fanuc series 0i-MF CNC, Mastercam CAD/CAM software, and a Chien Wei CMM. But the profile complexity of cycloidal gears meant that CMM data was inadequate — and customers purchasing the machines also had to buy expensive CAD/CAM software. So now, Chien Wei gear grinders include NUM profile grinding technology for simple, accurate, and flexible manufacture of both cycloid and involute gears.

Cycloidal gearing has few moving parts and efficiencies of 93% or better. Single stator-rotor combinations have ratios to 300:1.

Chien Wei’s internal gear grinder is a nine-axis machine. A workpiece table rides a linear axis that moves towards a belt-driven grinding wheel on a linear-motor-driven vertical axis. The grinding wheel spins as the linear motor moves it up and down … all while the workpiece table continually advances. Both gear flanks are ground simultaneously. The machine also handles gear dressing with a disc and grinding wheel.

The external gear grinder is an eight-axis machine — also with a direct-drive grinding wheel. Both machines include Flexium+ 68 CNC controls, FS153i HMIs, DXF file compatibility, and extensive machining databases. For more information, visit designworldonline.com and search Chien Wei. Planetary gearing is a mainstay in myriad applications.