VIDEO RASTERING TRAINING
inspector to make meaningful deci- sions. In addition, 71% of the time, the search pattern was not consistent with the one used for the immediate pre- ceding casting of the same geometry. Figure 4 shows the results from another field study at a metalcast- ing facility producing large castings (greater than 1,000 lbs. [450 kg]). Te initial results from the eye tracker showed a random search pattern used to inspect the castings, which led to only 84% coverage of the casting surface. After some basic rastering training, where the operators were instructed to use a consistent left to right search pattern, the eye track- ing results were again collected. Tis time, 96% of the casting surface was adequately covered.
Determining Methods to Improve Visual Inspection
Te field studies showed operators
were not using a consistent search pattern nor was there adequate cover-
As it proved to be impractical to have an overlay projected onto the casting surface, another experiment was conducted to investigate methods of improv- ing rastering. A video training was created to train subjects to move their eye in a systematic search pattern by following a prompt on a computer screen, at first across a blank screen and then over casting images. The field studies showed a very strong tendency for operators’ view to reach the edge of the casting and then follow the edge and miss the center area of the casting. Therefore, the video train- ing specifically had the search path run over the edges of the castings. This research showed video rastering training increased the percentage of unacceptable areas that were correctly identified, or an increased “hit rate.” The training also caused more areas that were acceptable to be marked as unac- ceptable, or increased the “false alarm” rate. Subjects saw more of the surface but had the same difficulty in discriminating between acceptable/unacceptable surfaces. The video files for the rastering training are available by contacting Frank Peters:
fpeters@iastate.edu.
age of the casting. To help alleviate these problems, laboratory stud- ies were conducted on methods to improve the search pattern as well as to study the ability to discriminate between surfaces. In the first experiment, three
conditions were tested related to the training and inspection aids provided
to the subjects. Te first group was only given instructions on what surface indications for which they were to look, but was not instructed on how to inspect the castings (basic training group). Te second group received the basic training as well as using a left to right search strategy called rastering (raster group), with instructions to
January 2014 MODERN CASTING | 45
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76