DIMENSIONAL TOLERANCE AND MACHINABILITY OF GRAY CAST IRON V. Jamerson—Undergraduate Student
Missouri University of Science and Technology, Rolla, MO, USA
Copyright © 2010 American Foundry Society Introduction
An experiment was designed to analyze the effects of dimen- sional tolerancing on machinability of industrially produced gray cast iron AFS 5J Machinability disks. The experiment used a laser profilometer to measure surface tolerance prop- erties in accordance with ISO 8062-31 Y14.43-20032
. Using the ASME
standard locator pins to define the location of fixed planar and cylindrical surfaces. The surface flatness was statistically evaluated and used to calculate geometry dependent machining allowances.
AFS 5J machinability castings, hereafter referred to as disks, were produced using green sand molds, made on a Herman molding machine, in an industrial trial. Four disks randomly selected from a batch of twenty class 30 gray iron disks were shot blasted to simulate regular foundry practices.
Experiment
The tools used in this experiment were a laser profilometer and a rotary machining table. The laser profilometer mea- sures the distance between itself and the disk. A computer collects the data, which is later analyzed for the surface properties (i.e. Ra, Rz, and flatness).
The disks were measured in two different orientations, stan- dard and random. The standard orientation is defined by the location of the ingate at pin B (figure 1) and the random orientation is defined by removing the disk and changing the location of the ingate to a random degree of rotation. • The dimensions of each disk and the gauge R&R were measured (table 1, table 2, and figure 2).
• Each casting was placed in a dimensional fixture on five locator pins (figure 1). The disk was then placed in a standard orientation and measured in 90 degree intervals using the laser profilometer. Each casting was then randomly placed and measured.
•
• The data was collected and analyzed in an Excel program.
Results
After the measurements were taken and analyzed the aver- age flatness values of each disk were compared.
In figure 4 the differences are negligible, since the difference in measurements is less than the difference the gauge R&R re- sults. Thus the random orientation of the casting does not make a difference when measuring the surface properties of the cast- ing, as long as three points are used to define the cope surface.
Table 1. Each Disk was Measured and Had Equal Dimensions to Within 1/16”
Table 2. Gauge R&R was Done to Test the Validity of the Instrument
Table 3. Surface Parameter Measurements from Each Disk
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International Journal of Metalcasting/Winter 10
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