fast-accurate and both the reflective and impulsive groups. Interestingly, the fast-accurate group did not have significantly different time compared with the slow-inaccurate subjects. Tis is attributed to the slow-inaccurates speeding up to get done with the task. Tis conclusion is supported by the accuracy of decisionmaking among fast-accurates, which was superior to the other three groups. In conclusion, the MFFT was
shown to be useful in determining the cognitive ability of personnel and there was a correlation between cognitive style and performance on a visual search task. Tis test could be used as a screening tool for new operators, or to identify the need for additional training and inspection aids among existing and future operators. It should be noted that underlying cognitive ability cannot be improved through training, but the strategies in which a person inspects a part can be improved to compensate for lower abilities.
Field Study Results
Field studies were conducted at steel and iron foundries producing shell, investment, chemically bonded sand and green sand molds for castings from 1 to 10,000 lbs. (0.5 to 4,500 kg). An eye tracker was developed so studies of the search strategies being utilized during the inspection process could be determined (Fig. 2). Tis tool allows analysis of the search pattern as well as determining the percent of the casting surface that is being inspected. It is mounted on a face shield and goggles to provide eye protection. Tis is often used in the shop floor environment. Te eye tracker has three cameras, two recording the world view in front of the operator and the other records the location of the pupil within the eye. Two cameras on the world view are necessary to collect data on operators that are inspecting larger castings. Te video from the two world view cameras is stitched together, then the world view and the
pupil view are compiled into a video of the world view with crosshairs to show where the user was looking at any given time. Tis compiled video can be analyzed, frame by frame, to determine the operator’s search patterns. To understand the results of the
eye tracker, the useful field of view (UFOV) needs to be defined. UFOV is the area where humans can see the most detail in their vision due to the greater concentrations of rods at that particular location. For the purpose of this study a reasonable value of 6 degrees is assumed. Assuming that the parts were 22 in. (56 cm) from the operator’s eye, the useful field was calculated to be 2.25 in. (5.7 cm) wide. Figure 3 shows an example of a casting with the search path line and the useful field of view overlaid on the part. For data collected on castings up to approximately 15 in. (38 cm), the eye track revealed that on average, 59% of the casting surface was not being viewed sufficiently enough for the
44 | MODERN CASTING January 2014
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