Federal Products Model 832 Gaging Amplifier Benefits Digital displays eliminate subjective measurements Factory calibrated system Requires fewer calibrations www.fedgage.com

Digital Gages Improve Accuracy

Haldex Barnes, a large manufacturer of hydraulic gear pumps and power units, realized substantial productivity and quality improvements by switching from analog to digital display technologies in a variety of shop floor gaging applications. Haldex Barnes found the displays on Federal Products Co.'s Model 832 Gaging Amplifier, used with Federal Products' LVDT electronic gaging probe, to be more reliable and less subject to subjective interpretation. With the help of these digital gages, Haldex Barnes' downstream assembly operations that depend upon the machinists' shop-floor readings are now performed more accurately, resulting in better pump assemblies and fewer rejects.

 Haldex Barnes' GC series of gear pumps have cast-iron housings whose machining requires strict control over multiple critical dimensions, including bore diameters, gear pocket depths and diameters, and distance between bearing bore centers. The most critical is gear pocket depth, which machinists measure at several locations on each pump housing.

 For this application, Haldex Barnes used to rely on analog amplifiers, which often produced unclear readings. The analog displays left too much room for operator interpretation, especially when the needle fell between two ticks on the dial. "We've eliminated assembly errors, because the digital display can't be misinterpreted," explains Deb Miller, gage calibration technician.

 Federal Products' gaging system eliminated the uncertainties associated with the analog gaging process. The LVDT is clamped in a flat, hand-held fixture that the machinist references against the part's mating surface. To take a measurement, the user locates the LVDT contact on the feature, presses down and reads the Model 832 amplifier's digital display. Miller notes that users can also program the Model 832 amplifiers to automatically classify parts into size categories using built-in indicator lights.

 Haldex Barnes completely eliminated analog gaging throughout the GC pump production area, replacing dial indicators on bore gages with Federal Products' Maxum electronic indicators and exchanging analog air gages for Federal Products' Digital Dimensionair air gages. The air gages, which are used to measure distance between bearing bore centers, are equipped with custom gage tooling, also from Federal Products. Another Model 832 amplifier is used at a surface-plate setup to capture total indicated reading data for flatness and parallelism of the parts' upper and lower surfaces.

 "The gaging itself hasn't changed, but we're doing more accurate work and producing better products because of the switch to digital displays," adds Miller. "It also gives us the capability to capture measurement data electronically." Miller notes that all of the digital display technologies from Federal Products support direct output to data loggers or computer networks.

 The digital gages also require adjustment less frequently than do analog systems. "Prior to going digital, the gages in this department had to be calibrated every 30 days," Miller points out. "Now, we calibrate every six months, and most of the gages don't require any adjustment on that schedule." This decreased need for recalibration results in overall greater physical reliability.