Albion Devices, Inc.

Case study: 7 years of Piston Skirt diameter temperature compensated gaging

 

• Capital Cost: $25,000 vs $1,000,000, saving of $975,000 or 97.5%

• Improved accuracy and quality control: maintained +/- 1 micron

• Inventory reduction: 8 classifications reduced to 2

• Faster quality assurance feedback: no waiting for parts to thermally normalize

 

A major car manufacturer planned to install a manufacturing line in one of their engine plants to make aluminum pistons. A previous piston line that had been installed in the same plant had been equipped with a special 68°F / 20°C temperature controlled “blockhouse” to accommodate the final skirt diameter and piston bore inspection gages and accumulators. The accumulators held hundreds of pistons that moved slowly through the air-conditioned environment so as to thermally stabilize before gaging.

 

It was estimated that a similar block house and accumulators for the new line would cost approximately $1 million. Engineers decided, after some discussion and skepticism, to use automatic temperature compensation systems on the gages, instead of the block house, at a total cost of $25,000. Albion provided the plant’s Manufacturing Engineer with a written understanding of system acceptance criteria that guaranteed that the system would compensate for not less than 90% of temperature induced error. More specifically, it was agreed that system performance should be demonstrated by measuring a piston skirt at stable temperature, then heating it by 20°F. It was estimated that the critical piston skirt diameter would grow by 28 microns under these conditions. Albion would therefore have to repeatedly correct the gage to within +/- 1.4 microns (correcting for 90% of 28 microns) in order to be accepted.

 

Albion installed its systems on two automatic gages that inspected 600 pistons per hour, 24 hours a day, seven days a week, built by a non-related company. The line was tested, and subsequently went into production. The tests, and subsequent monitoring over a period of 7 years, showed that the temperature compensation system consistently corrected for over 97% of thermal errors. Pistons could be inspected to within better than +/- 1 micron repeatability regardless of ambient temperature changes and process variations. The systems were deemed to have met acceptance criteria without hesitation. The plant Quality Manager stated that the compensation system worked better than the blockhouse did on the earlier production line. The plant was able to meet its goal of reducing the number of size classifications from 8 to 2, with 92.7% of pistons being in a single classification, thus helping to reduce inventories and on-floor selection for fit.

 

Over subsequent years the Quality Manager would frequently verify the performance of the temperature compensation system by running his “gold standard” pair of pistons through the gages. Regardless of temperature, he would always get repeatable dimensional measurements on these pistons to within +/- 1 micron. Albion’s temperature compensation systems remained in operation without the need for repair for the entire 7 year life of the production line before it was discontinued. A workpiece temperature sensor was replaced just once in all that time. The temperature compensation system performed better than the older block house did in terms of correcting for errors caused by temperature variations, yet cost only 2.5% of the original proposed cost of the block house. The temperature compensation system incurred virtually no running or maintenance costs. It also gave much quicker feed back to operators, since pistons did not have to spend 45 minutes passing through accumulators before being gaged.

 

 

After this installation the plant placed orders for several more temperature compensation systems from Albion for many different applications. They were installed successfully on gages that inspected such components as crank shaft journals, cylinder bores, crank bores, cylinder heads and con rods as well as pistons, with similar beneficial results. In addition, Albion temperature compensation systems have since been installed widely on piston gages operated by many other well known piston manufacturers.