Design of experiments to analyze factors for block digestion affecting the defect of nitrogen tubes
10.14416/j.ind.tech.2025.08.011
Keywords:
Factorial design, reducing defect, digestion tubeAbstract
This research aims to reduce the waste of nitrogen tubes generated from testing for the quantities of Nitrogen and crude protein in laboratory settings of a case study factory, using 2k Full Factorial Design. The study to identify factors and their levels in adjusting the settings of the Block Digestion machine appropriately. The experimental design comprises three main factors: temperature, burning time, and cooling time. The experiments were repeated three times, totaling 24 trials. The experimental results indicated that temperature, burning time, and cooling time had a statistically significant effect on the occurrence of cracks in the test tubes at the 95% confidence level. Moreover, significant interaction effects were observed between temperature and burning time, as well as between temperature and cooling time and the appropriate factors and levels for adjusting the settings of the Block Digestion machine are: temperature at 400 degrees celsius, burning time of 120 minutes, and cooling time of 50 minutes. Subsequently, the appropriate factors and levels were used to collect data for comparison before and after adjustment. It was found that before adjustment, there were 359 instances of tube damage, whereas after adjustment, the instances reduced to 7, resulting in a reduction of waste by 98.05%. When comparing the expenses incurred, it was found that before adjustment, the cost of the 359 damaged tubes amounted to 502,600 baht, with a unit cost of 1,400 baht per tube. After adjustment, with only 7 damaged tubes, the cost amounted to 9,800 baht, resulting in a reduction in expenses by 492,800 baht.
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