Supersized Surface Profiling System Inspects Large Bearings

A system for measuring bearings up to 84 inches in diameter involves moving the gage and granite surface plate to the workpiece with air-bearing assists.

Case Study From: 4/3/2007 Modern Machine Shop

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Air-bearing assists move the gage

Air-bearing assists move the gage, which is placed on a granite surface plate, to the workpiece so that the operator need not orient the piece to the gage.

Inspecting the surface finish of bearing parts often entails mounting the parts on a sine plate positioned near a surface-finish drive unit. This traces the part profile parallel to a granite surface plate that supports the sine plate and the traverse unit. Though normally sufficient, this approach may be impractical when the parts weigh nearly 1 ton.

One bearing manufacturer worked with Detroit Precision Hommel to develop a custom surface-finish measuring system for a range of particularly large bearings. A total of four of the ergonomically-designed systems have been purchased for manufacturing plants in the United States, Europe and Asia.

The company’s cylindrical and tapered raceway bearings for industrial applications measure 4 to 30 inches high and range in diameter size from 8 to 84 inches. Because of their unusually large size, the bearings require an innovative workholding strategy that minimizes material handling while maximizing operator safety. The solution involves moving the gage, which is placed on a granite surface plate, to the workpiece with air-bearing assists. This eliminates the need for the operator to orient the piece to the gage.

The bearings are positioned on their faces on the granite plate. The traverse unit is tilted to orient the drive unit parallel and square to the raceways to measure outer and inner cylindrical races as well as tapered cups and cones.

To stretch measuring flexibility, the traverse unit can be positioned in virtually any orientation, including vertically, horizontally and upside down. It can be mounted at any angle between -45 degrees and 135 degrees to measure all surfaces of the large parts without the need to move them.

Also essential is extreme traverse straightness, which must be less than 2-microinch deviation per inch of traverse. The traverse unit travels back and forth on the races for positioning and does not require “homing” prior to measurement. The motor-driven column provides X- and Z-axis control of final positioning to ±0.050 mm or less. The smallest measurement range is ±80 microns.

A Windows-based software package provides bearing raceway profile information and key performance data to allow the customer to evaluate the profile for process control and inspection purposes.

Specifically, the bearing measuring system includes a Hommel Tester T8000 with Windows-based programs for checking roughness, topography and contour for the evaluation, recording and graphical representation of measured values.

The traverse unit, the Hommel waveline 200, has tracing speed ranging from 0.01 to 0.03 mm/sec. and positioning accuracy of less than 10 microns over a total traverse length of 200 mm. The unit permits a high data-logging rate and bidirectional measuring, the manufacturer says. All waveline components are controlled by a CAN bus. An eight-piece pickup set permits tracing grooves, collars, faces and other features.

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