The stamping operation stretches the steel but gage variations often escape visual detection in the early processing stage. Only after polishing and painting changes the surface reflectivity of the metal does the gage variation manifest itself as light and dark lines, called tiger striping in the industry. Extreme vibration problems in a rolling mill can cause a break in the metal sheet during the rolling process, the cost of which goes far beyond the loss of raw material. The mill may be shut down for hours while maintenance personnel clear the loose metal and make necessary roll repairs or replacement. This requires the use of a dynamic signal analyzer, such as an SPS395, to diagnose the source of vibration problems.
Data flows in at a rapid rate, especially with a multichannel system.
During post-test analysis, the investigator can replay the time history and pick the results apart millisecond by millisecond and change the display format for best viewing perspective. Transducers that combine a low profile with high sensitivity are the most convenient choice for working within the space limitations present on most rolling mill stands. Powering the transducers from the analyzer eliminates external power conditioners and additional cabling. If defects are found in coils emerging from a five-stand mill, the analyst will begin by instrumenting the top and bottom roll chocks of the fifth stand. He will then sequentially check each preceding stand.