An intelligent shop floor quality-
inspection strategy is helping Haldex Barnes Corp. manufacture hydraulic gear pumps accurately and efficiently at its Rockford, Illinois, facility. Using Mahr Federal Inc.'s
FedCheck Gaging Computer and Software with special bench fixtures, Haldex is able to monitor and maintain the quality of three different parts concurrently at a single shop floor gaging station.
Haldex Barnes' 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 lines, each with a different aluminum housing, form the basis for a wide range of submodels. The aluminum housings
offer 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.
Haldex 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 not constant, Haldex determined
that a single shop floor gaging station--equally accessible to machinists working on all three product lines--would serve the need. The trick, however, was to
make the inspection process so efficient that parts from the three lines 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," says Deb Miller, a gage calibration technician at Haldex. "The shop floor
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 Haldex contacted Mahr Federal, which responded with three custom-engineered bench fixture gages connected to a single FedCheck
Gaging Computer and Software package. A Mahr Federal air plug gage, whose use is common to all three parts, is also connected to the computer
through an air-to-electronic conversion module.
All four gages sit side by side on the bench, with the computer on a shelf
above. When machinists need to measure parts, they begin 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 (ID) measurement. Then the operator turns the plug 90 degrees for a second ID 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 of the LVDT signals in isolation and combines others mathematically to
capture or calculate values for two gear-pocket diameters, center distance between two dowel bores, and the 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 need only glance at 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.
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 shop floor quality control needs for the entire W Series product line, enabling operators to return to their machines without
delay. The system provides high accuracy and 100-percent data capture for quality documentation, helping the company maintain overall quality, as well as ISO 9001 certification.
FedCheck Gaging Computer and Software is a 32-bit system that 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 powerfully 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.