Applications

Crank Shaft 
Aluminum Engine cylinder and crank bores
Piston skirt ODs
Wrist pin ODs
Brake drums
Bearing races  
In-Process gaging


Application notes for other component gaging are available from Albion. Just call us at 858-792-9585

APPLICATION NOTE

CRANK SHAFT - ALUMINUM AUTOMOTIVE ENGINE

Customer: Big Three auto manufacturer

Application: 3.5/3.8L Engine Crank Shaft

Measurements: Gage measures diameters of four bearing journals, at three locations on each journal.

Compensation Approach: Albion’s GageComp Temperature Compensation System uses two sensors to monitor temperatures of

a) workpiece and master and

b) gage fixture.

GageComp computes and transmits a correction factor via RS232 signal to a semi-automatic gage computer (built by Detroit Precision Tool Co.), where correction amounts are calculated for each of the critical measured dimensions and mixed with gaged dimensions to give resulting net compensated measurements for each feature.

Gage Modification: An IS-1 workpiece/ master temperature sensor was mounted in the gage so that it would come in contact with bearing journal #2 of the part, and the respective location on the master, when each was in the gage. In addition, a GS-1 gage sensor was positioned to monitor the temperature of the gage fixture itself.

Characterization: To determine effective coefficients of expansion (COEs), empirical testing was performed on the master, sample crank shafts and gage fixture (the "elements" of the measurement system). The uncompensated gage was first used to make measurements for these tests with compensation turned off, so that true changes in dimension could be noted. Compensation was then turned on, to verify the results.

Since there were four journals (features) and three elements to be considered for each feature, twelve characterization studies were conducted. In each case, one element was varied in temperature while the remaining elements were maintained at stable temperature. Any variation in dimension could then be attributed to the element that had been subjected to varying temperature. From the recorded data a linear correction coefficient, which took into account expansion coefficients, thermal gradients and locational considerations relative to the temperature sensors, was determined for each element (see Fig. 1), and its affectivity demonstrated ( see Fig. 2).

Fig. 1 Effective COEs found for each element.
(µm/m/ºC= parts per million per degree C)

Fig. 2  Bearing OD data taken from gage while crank shaft was heated and gage was held at stable temperature. Note red line shows uncompensated growth caused by increase in temperature.

Implementation: This gage is used to measure crank shaft journals after they have been washed. They are warm to the touch when gaged and they are rotated while being measured. Each crank shaft is first hand loaded onto an elevator mechanism which then places the part into gaging position on V blocks. The temperature sensors are mounted in one of these blocks. The IS-1 workpiece/master sensor is positioned so that it makes contact with a journal.

The GageComp is programmed with four separate sets of feature parameters, one for each journal. Each feature contains settings specific to one journal.

The host computer communicates with the GageComp and cycles through the features to obtain the correction for each journal. It adds this correction to the measurements taken for the respective journal so as to arrive at a net temperature corrected measurement.

The output therefore represents the dimension of the journal as if it, and the gage and the master, were each at a steady 68°F (20°C).

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APPLICATION NOTE

ALUMINUM ENGINE CYLINDER AND CRANK BORES

Customer: Big Three Engine Plant.

Application: Aluminum 3.5 liter engine block with cast iron cylinder liners.

Measurements: Hand held gage heads (plugs) measure diameters of cylinder and crank bores.

Compensation Approach: Albion’s GageComp Temperature Compensation Systems on each gage use 2 sensors to monitor temperatures of a) workpiece and master and b) plug gage. GageComp receives dimensions via analog signal from LVDT conditioning circuit boards in electronic columns (built by Giddings and Lewis, Measurement Division), corrects the dimensions for thermal errors and outputs resulting net compensated measurements back to the columns for display .

Gage Modification: The gage heads, manufactured by Intra Corporation, were engineered to Albion specifications so as to minimize thermal effects. They were hollow, so as to reduce total mass, and had material removed from non-critical exterior surfaces so as to reduce contact between gage and workpiece. Bore holes were made in the gage heads to accommodate Albion’s IS-2 workpiece/master bore temperature sensors which make contact with the inside surfaces of the cylinder and crank bore walls and of the masters. GS-2 needle sensors were positioned inside the gage head walls to correct for thermal effects on the gages themselves.

Characterization: To determine effective coefficients of expansion (COEs), empirical testing was performed on the master, sample workpiece (engine block) and gage head (the "elements" of the measurement system). The uncompensated gage was first used to make measurements for these tests with compensation turned off, so that true changes in dimension could be noted. Compensation was then turned on, to verify the results of the thermal correction applied.

Interesting Observation: It was determined that the coefficient of expansion (COE) for the cylinder liners was that which you would expect for aluminum rather than for cast iron, indicating that thermal effects on the aluminum block created overriding stresses in the cast iron linings.

It was found that the cylinder bore expanded at the rate of 2 microns per °C, and the crank bore expanded at the rate of 1.5 microns per °C. Using the coefficient of 24 parts per million per °C, Albion’s system is able to compensate for over 97% of thermal effects in the cylinders over a 25°C range, from 20°C to 45°C (see Fig. 1).

Fig. 1 Sample data from characterization study, taken as cylinder block varied in temperature while measurements were taken. Temperature compensation was switched on, then off, each time a measurement was taken, so that results could be compared.

Fig. 2. Sample data from characterization study. Results from heating Crank Bore Gage Head and taking repeated measurements as it cooled. Note linearity of size contraction, and effectiveness of compensation.

Implementation: This hand held gage is being used to audit machining and automatic gaging processes. Whereas the block is machined in temperature controlled coolant, the auditing may take place several hours later, after the block has changed temperature. There had always been difficulty in correlating measurements until thermal variables were eliminated.

The solution to the problem was found through studies to determine the most effective placement and design of temperature sensors and gage head. Several new and innovative design concepts were incorporated into the final gage configuration as a result.

APPLICATION NOTE

PISTON SKIRT DIAMETERS

Customer: Big Three Automotive  Engine Plant.

Application: V8 Piston skirt OD gages built by Air Gage Co.

Measurements: Automatic and Bench Top Gages measure piston skirt outside diameters.

Compensation Approach: Albion’s GageComp Temperature Compensation System uses 2 sensors to monitor temperatures of A) workpiece and master and B) gage fixture. Sensor A measured the temperature of the piston body at the skirt dimension level. Sensor B was buried inside each of the gage fixtures. GageComp measurement via analog signal to the gage computer where correction amounts are mixed with gaged dimensions to give resulting net compensated measurements.

Gage Modification: The gage fixture was modified to include a 3/8" bore to house the workpiece/master temperature sensor. The workpiece sensor was positioned so that it came in contact with the outer body of the piston.

A 1/2" bore in the gage fixture housed a thermistor which monitored the temperature of the mass of the gage.

Characterization: To determine effective coefficients of expansion (COEs), empirical testing was performed on the master, sample workpiece and gage fixture (the "elements" of the measurement system). The uncompensated gage was first used to make measurements for these tests with compensation turned off, so that true changes in dimension could be noted. Compensation was then turned on, to verify the results of the thermal correction applied.

Characterization studies were conducted for each element. In each case, one element was varied in temperature while the remaining elements were maintained at stable temperature. Any variation in dimension could then be attributed to the element that had been subjected to varying temperature. From the recorded data a linear coefficient of expansion was determined  and its effectivity demonstrated (Fig1).

Fig. 1 Skirt OD data taken from gage while piston was heated and gage was held at stable temperature.

Fig. 2 Skirt diameter measurements when gage fixture was heated.

APPLICATION NOTE

BRAKE DRUMS

Customer:  American Axle Manufacturing Inc.

Application: Automatic gaging of drum and pilot bores.

Measurements: K.J. Law Engineers automatic gage (Ultragage) is used to control dimensions in the brake drum production process. The gage is positioned immediately after a hot washing process, so parts can vary considerably in temperature. The pilot bore is air gaged while part is stationary. The drum bore is measured with contact gaging while the part is rotated.

Compensation Approach: Albion’s GageComp Temperature Compensation System uses 4 sensors to monitor temperatures of a) workpiece and master and b) gage fixture in each of the two measuring stations. GageComp computes and transmits correction via analog signal to Ultragage, where correction amounts are mixed with gaged dimensions to give resulting net compensated measurements for each bore diameter.

Gage Modification: The gage heads were engineered to include 2 of Albion’s IS-1 workpiece/master temperature sensors. The sensors were positioned so that they came in contact with the machined surfaces of the drums. 2 GS-2 gage temperature sensors were also mounted in the gage heads.

Characterization: To determine effective coefficients of expansion (COEs), empirical testing was performed on the masters, sample workpieces (brake drums) and gage head (the "elements" of the measurement system). The uncompensated gage was first used to make measurements for these tests with compensation turned off, so that true changes in dimension could be noted. Compensation was then turned on, to verify the results of the thermal correction applied.

Since there were three elements to be considered for each station, six separate characterization studies were conducted. In each case, one element was varied in temperature while the remaining elements were maintained at stable temperature. Any variation in dimension could then be attributed to the element that had been subjected to varying temperature. From the recorded data a linear coefficient of expansion was determined for each element  and its effectivity demonstrated.

APPLICATION NOTE

BEARING RACES

Customer:  MRC Bearings, Jamestown, NY

Application: Measuring bearing race ODs.

Measurements: Tabletop adjustable "banjo" gage with Federal Products LVDT and Amplifier measures various bearing race ODs from 3 inches to 18 inches. 

Compensation Approach: Albion’s GageComp Temperature Compensation System uses 2 sensors mounted in gage fixture to monitor temperatures of A) rim of bearing race and master and B) gage fixture. Federal Amplifier sends measured dimension via analog signal to GageComp. GageComp computes thermal correction and displays corrected measurement.

Gage Modification: The gage fixture was modified to include a 3/8" bore to house the workpiece/master temperature sensor. The sensor was positioned under the LVDT tip so that it came in contact with the face of each race and master at the time either was in position in the gage. A 1/4" bore was also added to the fixture, to house the gage thermistor.

Characterization:

To determine effective coefficients of expansion (COEs), empirical testing was performed on samples of the smallest and largest races and the gage fixture. Since the masters were sample workpieces it was not necessary to do separate characterization work on them.

During testing, the measurement system was first used to make measurements with compensation turned off, so that true changes in diameter could be noted. Compensation was then turned on, to verify the results of the thermal correction applied.

In each case, one element was varied in temperature while the remaining elements were maintained at stable temperature. Any variation in dimension could then be attributed to the element that had been subjected to varying temperature. From the recorded data a linear coefficient of expansion was determined for each race. Since the correction coefficients were linear and very similar for both small and large races, it was considered reasonable to use one average coefficient for each race and gage set-up for each dimension to be measured over the range of races produced at the production station.

Fig. 1 Sample data from characterization study, taken as a 7 inch bearing race was deliberately varied in temperature by approximately 20°F while measurements were taken. Temperature compensation was switched on, then off, each time a measurement was taken, so that results could be compared.

Fig. 2. Sample data from characterization study. Results from heating bearing gage fixture and taking repeated measurements as it cooled.

APPLICATION NOTE

PROCESS IMPROVEMENT FROM TEMPERATURE COMPENSATION OF IN-PROCESS GAGES

Certain machining operations, such as grinding, are often controlled through the use of In-Process gages. However, the act of machining frequently puts more energy into the workpiece and gage than can be removed by coolants, while machine and shop floor temperatures are subject to drift. Consequently, significant thermally induced measurement errors can be encountered.

A study at a major manufacturer of bearings has confirmed this. The study also showed that the use of Albion’s specially designed contact sensors can allow temperature compensation systems to minimize these effects, thereby contributing to very large improvements in process capability.

Tests conducted on a 4 inch / 100mm internal diameter bearing race grinder showed that the races heated to as much as 150°F / 65°C during rough grind, even while being flooded in coolant. During the finish grind cycle temperatures only dropped to about 120°F / 50°C. Reference temperature is the ISO 1 standard 68°F / 20°. Measurement errors in excess of .001 inch / .030 mm can result from such temperature variations on a part of this size.

In the test, two pairs of data sets were obtained. First, 25 pieces were run through the grinder without temperature compensation turned on. The parts were temperature stabilized and measured by a temperature controlled gage as they came off the grinder. The next 25 parts were produced with temperature compensation turned on, using Albion’s DS-1 sensor on the in-process gage. The same procedure was followed for the second pair of sets, except that in each run 50 parts were used instead of 25.

As the accompanying data show, the use of Albion’s sensors during real time temperature compensation of the in-process gage directly led to Cp and Cpk improvements of 100% to 200%. Click on the thumbnails below to see the charts and data.

Test 1 a): 25 parts per run, without in-process temperature compensation.                 

Test 1 b): 25 parts per run, with in-process temperature compensation.

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