'Smart' Gaging Helps Pump Maker Gain Production Efficiency

A FedCheck computer and custom gage fixtures from Mahr Federal give Haldex Barnes the ability to maintain process consistency.

An intelligent shopfloor quality inspection strategy is helping Haldex Barnes Corp. manufacture hydraulic gear pumps accurately and efficiently at its Rockford, IL, facility. Using a FedCheck gaging computer and software, plus special bench fixtures engineered by Mahr Federal Inc. (Providence, RI), Haldex Barnes can monitor and maintain the quality of three different parts concurrently at a single shopfloor gaging station.

The company's W Series high-performance hydraulic gear pumps and fluid motors are used in material handling, turf, and construction equipment, as well as other applications. Three product families, each with a different aluminum housing, form the basis for a wide range of sub-models. The aluminum housings contain numerous machined features, including two bearing bores, four dowel pin bores, two overlapping gear pockets, tapped inlet and outlet ports, and precision upper and lower faces. Most of these features have tight tolerances and geometric dimensioning for out-of-roundness, distances between centers, flatness and parallelism of faces, pocket depth, and more.

Periodic Inspections
Haldex Barnes machinists need to check many of these features during setups, and periodically during production to maintain process control. Because the need for inspection at this stage of production is periodic, not constant, the company determined that a single shopfloor gaging station — equally accessible to machinists working on all three product families — would meet the need. The trick, however, was to make the inspection process so efficient that parts from all three families could be checked randomly by several machinists without causing delays that would slow production.

"We considered a CMM for the application, but that wasn't practical," said Haldex Barnes Gage Calibration Technician Deb Miller. "The shopfloor environment where we perform the measurements isn't conducive to CMM reliability, and taking the parts out of the production area to a stable environment would be terribly inefficient. CMMs are also too slow to measure these parts efficiently, and most of them just aren't accurate enough for our needs."

So the manufacturer contacted Mahr Federal Inc. (Providence, RI), which responded with three custom-engineered bench fixture gages connected to a single FedCheck gaging computer/software package and an air plug gage connected to the computer through an air-to-electronic conversion module.

Gaging Station in Action
All four gages sit side-by-side on the bench, with the computer on a shelf above. When a machinist needs to measure a part, he or she begins by selecting the appropriate part program from a screen menu on the FedCheck. The computer displays the part image, with all relevant tolerance specifications.

The operator inserts the air plug into a dowel bore, and the FedCheck records the inside diameter measurement. Then the operator turns the plug 90°-for a second I.D. reading, and the computer calculates a two-point out-of-roundness value from the difference between the two measurements. The second dowel bore on that side of the part is measured the same way.

Next, the part is placed on the appropriate bench fixture, using the dowel bores as references. Each fixture has seven LVDT-type transducers contacting various part features, either directly or through linkages. The computer uses some LVDT signals in isolation, and combines others mathematically, to capture and/or calculate values for two gear pocket diameters, center distance between two dowel bores, and position of the two gear bores relative to the dowel bores. The part is then flipped over, a similar series of measurements are performed on the reverse side, and the two sides are compared.

The FedCheck displays all the dimensions simultaneously in "column gage" format. Because the columns change color, depending upon whether a dimension is in or out of tolerance, the operator can check the computer screen to confirm that production remains in tolerance. If a part does contain an out-of-tolerance condition, the operator has the option of printing out a summary sheet of all the part's dimensions; this is tagged to the part for future analysis.

Saving Time, Building Efficiency
According to Miller, it takes less than 20 seconds to measure 27 critical dimensions using the multistation gage. Consequently, the single gaging station is able to efficiently serve the shopfloor QC needs for the entire W Series product line, enabling operators to return to their machines without delay. The system provides high accuracy and 100% data capture for quality documentation, helping the company maintain overall quality as well as ISO-9001 certification.

Miller said that Mahr Federal's local sales engineer, Steve Cobert, provides Haldex with invaluable help in determining the nature of the gaging required, coordinating its design by Mahr Federal's special gaging engineering staff, setting up the gages, and programming the gaging routines. "Mahr Federal's sales force is somewhat unique, in our experience, among gage suppliers," she added. "They're not distributors' agents, they're gaging applications specialists. We depend upon Steve and Mahr Federal to help us solve quality and inspection problems."

The 32-bit FedCheck gaging computer and software can interface with virtually any dimensional gaging device. Available in both hardened industrial and benchtop versions, the system supports up to 32 gaging inputs and handles all aspects of computer-aided metrology including gage operation, closed-loop machine control, and networking. FedCheck software incorporates dynamic gaging functions; full equation capabilities; selectable resolution, offset, and calibration methods; multilevel security access; and customizable online help screens and reports. Statistics capabilities include real-time charting of variables and attributes; control limits; full SPC functionality; and flexible report generation.

For more information, contact: Mahr Federal Inc., 1144 Eddy St., P.O. Box 9400, Providence, RI 02940-9400. Tel: 800-FED-GAGE (U.S.) or 401-784-3252; Fax: 401-784-3246.