Table 4. L4 DOE results
Table 5. Shrinkage (inches) of Coated and Uncoated Cores After Oven Drying
the same mix using the casting plant’s “standard” conditions. The cores were then placed in the dial indicator fixtures, and the indicators were zeroed. Four of the cores were place in the CT room at 40% RH, and four were placed in the humidity chamber at 90% RH. After 24 hours, the indicators showed the cores stored at high humidity shrank an average of 0.0043 in. (0.11 mm) compared to an average of 0.0055 in. (0.14 mm) for the cores stored in 40% RH.
Conclusions
1. The DMAIC process as used at Ford’s Casting Plant is an effective method of investigating and resolving casting issues.
International Journal of Metalcasting/Summer 10
2. PUCB cores will experience a slight amount of shrinkage, in the range of around 0.1%, over a period of 24 to 48 hours.
3. The amount of shrinkage can be influenced by material and process variations, but the effects of these variations are less than the overall effects of time.
4. Coating and oven drying the cores “artificially ages” them and causes all the normal shrinkage to occur during drying with little or no additional shrinkage.
5. Exposure to high humidity can decrease the shrinkage of new cores or cause a slight expansion of aged cores.
6. Individual shrinkage studies may be needed to establish data for specific materials and operations. 7. Core shrinkage is relatively small and one of many
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