An Alternative Method to Methylene Blue Clay Test
Spectrophotometry could take subjectivity out of the molding sand test for better reproducibility and repeatability. A. PIKE, DARIUSH MORADINEZHAD, JAN PEKAROVIC AND SAM RAMRATTAN, WESTERN MICHIGAN UNIVERSITY, KALAMAZOO, MICHIGAN
T
he methylene blue clay test has been used as part of green sand control
programs to measure active clay content of molding sand since 1967, but its variability has been noticed since its first use. Te amount of live clay in a sand system is important. When clay becomes dead (unable to absorb moisture) after repeated use, it sacrifices mold strength. Recently, Western Michigan Univ.
(WMU), Kalamazoo, Mich., began research to develop an emerging ana- lytical method based on clay absorption properties as an alternative to the methy- lene blue clay test for higher accuracy, better cost efficiency and a cleaner test environment. Te principle of using dye absorption
for clay mineral measurements originates in the 1940s. In the late 1970s, analysis of dye absorption using a spectrophotom-
eter was proposed, but few metalcasters showed interest at the time. A later paper described using methylene blue as the working chemical for clay detection, but proposed a new method based on spec- trophotometry instead of the standard drop test. By ensuring an oversaturated solution, the absorbency of the solution is always greater than zero. It was found adding clay to the solution would pull the methylene blue out of the solution and reduce absorbency. Te authors dem- onstrated a linear relationship between the amount of active clay and absorbency of the solution. Te research team at WMU used
a spectrophotometer to determine the absorption or transmission of visible light by a sample to measure concentrations of absorbing material based on calibration curves. When possible, the WMU team based the methodology on the exist- ing methylene blue clay test. Te results showed the proposed spectrophotometry technique surpasses the methylene blue clay test in a Gage R&R measurement system analysis.
ONLINE RESOURCE Fig. 1. The left and right cuvette represents the sample before and after centrifuging. 36 | MODERN CASTING August 2013
For more about the methylene blue clay test and proper test- ing procedures, read “Avoid the Methylene Blue Blues,” Modern Casting, December 2008, p. 36-38.
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