Big or Small - Inspection is Key to Success
by Matthew Jaster, Senior Editor
While Hofmann, Rexnord and Ferry Capitain know big gears, companies like Carl Zeiss, Wenzel and Klingelnberg know a little bit about inspecting them.
"Nowadays, large toothed gears are subjected to the same requirements as smaller toothed gears in stationary transmissions or vehicle gearboxes. Beyond the quality of the gearing, inspections must be conducted on the surface of the tooth flanks and the dimensions and measurements of the workpiece must be analyzed as a whole," says Gunther Mikoleizig, product manager for precision measuring center, Klingelnberg GmbH.
The largest bridge type CMM Zeiss offers is a 2,000 mm x 4,200 mm x 1,500 mm (courtesy of Carl Zeiss).
"The actual inspection process for gears is quite simple," says Todd Woijoviets, technical sales engineer at Zeiss Metrology. "The challenge comes when we look at gear standards. Manufactures use different standards and different versions of the standard. This makes it difficult for everyone throughout the process because they must be up-to-date on all these standards and the changes between versions."
Klingelnberg offers measuring centers up to 4,000 mm O.D. (courtesy of Klingelnberg).
Safety, of course, is always one of the key parameters for large gears. "A precision test of all parameters on large toothed gears provides a higher level of safety for the components," says Mikoleizig. "An ongoing analysis of the results of the gear measurement can also provide helpful supplemental information, such as how to define or simulate the running conditions for the transmissions. This in turn produces shorter production and development times."
At Wenzel GearTec, the company manufactures traditional, horizontal arm gear testers called WGT, which are capable of measuring gears up to 3,000 mm in diameter (10 feet) and gantry-style vertical gear tester capable of measuring gears up to 4,000 mm (13 feet) in diameter. The vertical gantry-style machines called LHFGear also have the advantage of being able to measure large geometric, CMM parts, such as large bearing profiles and gearboxes on the same system and are also advantageous when measuring large internal gears.
Wenzel Inspection machines offer a full software suite, Barkhausen Noise Analysis and surface finish devices (courtesy of Wenzel).
"Portable gear testers can measure some gear features such as the pitch of adjacent teeth or lead and profile of individual teeth, but cannot accurately measure diameters (reference diameters or dimensions over pins), planes, run-outs and other geometry," says Andy Woodward, president, Wenzel America Ltd. "All Wenzel gear measuring machines offer a full software suite for any gear type and for gear cutting tools also. Barkhausen Noise Analysis (for measuring stresses or damage due to grinding burn) and surface finish devices can be added to any Wenzel system."
As a manufacturer of precision measuring centers, including for large and heavy workpieces of up to 4,000 mm outside diameter, Klingelnberg has been proactive in the development of equipment to test additional parameters within a clamping. This includes opportunities for measuring surface roughness or undertaking grinding burn tests.
"Measurement of the dimensions, shape and position of the drive components can also be undertaken, to deliver comprehensive measurements of all parameters for a workpiece," Mikoleizig says.
"Contact measurements are one of the best ways to inspect form and location of gear teeth. Plus with a Zeiss CMM, not only can you inspect the requirements of the gear but you can also inspect the housing of the gear, which is something that cannot be done with dedicated gear inspection equipment," Woijoviets says. "The largest bridge type CMM Zeiss offers is a 2,000 mm x 4,200 mm x 1,500 mm. Then we move into a gantry CMM. Our gantry type CMMs have a measuring volume of up to 5,000 x 7,000 x 3,500."
When Wenzel was presented the challenge of designing a CMM measuring solution for inspecting large ring gears and bearings for Liebherr Werk Bieberach GmbH, a German manufacturer of large construction cranes, the company designed and built a special CMM machine that combined their standard components and dual-arm measuring technology with the precision air bearing mechanics of the Wenzel WGT series of Gear Checkers.
"The inspection machine is capable of inspecting bearings and ring gears up to 6,000 mm (19.68 ft) diameter. The dual-arm machine design is similar to what Wenzel has applied in the automotive industry to measure car bodies and body components," Woodward says.
In this design, the CMM measuring arms are each mounted to a table that is mounted on a large corresponding granite base. The measuring arms feature high accuracy linear guideways for the X-axis. The Y- and Z-axes feature finely tuned preloaded roller bearings providing minimum friction and operational wear. The base units are positioned opposite each other with a rotary fixture table in between. Both arms measure the large rings concurrently, and the metrology of each measuring arm is harmonized through the use of a specially designed calibration tool.
"The ring gears and bearings are located and clamped on the 2,200 mm (7.21 ft) diameter hydrostatic rotary table that can handle loads up to 100,000 lbs. The complete circumferences of the rings are inspected by a single inspection part program. Application software is also provided that can calculate the optimum fitting tolerance for inner and outer bearing components."
So what's the moral of the story? Manufacturers of large and small gears can get technology that will make gear inspection easier and more user-friendly no matter the size requirements.