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문제 정의
- When deflection occurs due to deformation in the air suction unit, condensation occurs due to clearance of the insulator installed between the air guide and air suction unit. Thus, this study aims to replace the existing insulator and minimize the weight and deformation of the air suction unit by using microcellular foaming, which has excellent insulation characteristics, to prevent the condensation phenomenon occurring due to the deflection by the product deformation and the weight.
제안 방법
- 3 were used as the range of each level. Based on the 22 RSM results, variance analysis was conducted, including the second interaction, considering the second reaction model. The analysis result showed that the P values with regard to the quadratic squared term of molding temperature and cooling time were 0.
- 3. Based on the RSM results, variance analysis was conducted including the second interaction considering the second reaction model. The analysis result showed that the P value of the second interaction was 0.
- 5 mm, and the smallest deformation was changed when the width was 15 mm, regardless of the height. Based on the result from the experiment design, Pareto chart analysis was conducted according to the structure. The analysis result verified that the interaction of the width and height of the reinforced structure was not significant in terms of the deformation of the product, and that the width had more significant effect on the deformation than the height.
- This study applied microcellular foaming technology to reduce the production weight and deformation as well as achieve functional improvement of a 4-way panel in the ceiling-type air-conditioner produced by existing injection molding processes. In addition, regression analysis and RSM were used to derive the process conditions that minimized the product weight and deformation, thereby obtaining the following conclusions.
- This study applied microcellular foaming to the 4-way panel production process used in ceiling-type air-conditioners, thereby finding the process conditions that simplified the complex processes and reduced the high investment cost, as well as achieving light-weight product and minimizing deformation. The current process capability regarding product weight and deformation produced with existing injection molding was analyzed, and the influencing factors were selected on that basis.
- Thus, degree of the product deformation was checked in a range of 9-15 mm that displayed a correlation of the quadratic equation form, and the second regression analysis was conducted to calculate the width that induced the minimum deformation. The width used in the second regression analysis and the product deformation according to the width are presented in Table 2.
- 0 mm. Thus, mold temperature was predicted by conducting a regression analysis. The mold temperature that satisfied the target upper limit was 70℃.
- To calculate the optimization values of resin temperature (Tmelt) and injection speed (Vinj), which were vital factors that affected the product weight (W), 22 and RSM were employed. Each level was set based on the first optimization range in Section 2.
- To set up the upper limit of the dimensions and product weight, manufacturing date of the product, and lot number of the raw materials were classified to six groups, and five samples from each group were taken to measure the deformation and weight. To measure the deformation, the four supporting points used during product assembly were supported as shown in Fig.
- Two-factor by two-level factorial design (22 FD) was conducted using the 2.5D module of Moldflow to evaluate the effect of the structure in the product edges on deformation. To analyze the microcellular foaming molding, CO2 was used as a gas in the input conditions, and for cell's density and size, the results verified by the specimen were reflected.
대상 데이터
- The experimental analysis target was the air suction unit in the ceiling-type air-conditioner shown in Fig. 1. In the injection molding process, which was the existing production method, high-impact polystyrene resin was used.
- However, this study employed polypropylene (PP), considering the economic feasibility, in the microcellular foaming molding process used in this study. The product dimensions were 800 x 800 mm. The cooling was discharged and distributed by the air guide installed along the edges in the air suction unit in four directions.
데이터처리
- ANOVA analysis was conducted at mold temperatures of 30℃, 40℃, and 60℃ to analyze the correlation between mold temperature and product deformation. The analysis result verified that the P value was 0.
- The analysis results verified that the deformation was reduced as the width increased when the range was 3-12 mm, but the deformation started to increase when the width range was 12-15 mm. Based on this result, regression analysis was conducted. The results determined that the change in deformation in a range of 9-15 mm of width followed the quadratic equation form, and after a certain width, it was ejected before solidification, thereby playing a role in inducing deformation.
- For the weight difference according to the resin temperature, the product weight was compared when the resin temperature was 210℃, 230℃, and 250℃ using the ANOVA method. The analysis result showed that the P value was 0.
- In the same method, a cooling time was set to 20s, 35s, and 50s, and the levels of product deformation were analyzed via ANOVA. Similar to the molding temperature, P value was lower than the significance level, so it was selected as one of the few vital factors.
- Range of width was selected as 3-15 mm for the optimization of the edge width, and regression analysis was conducted based on the deformation calculated through the computer-aided engineering (CAE) analysis. The analysis results verified that the deformation was reduced as the width increased when the range was 3-12 mm, but the deformation started to increase when the width range was 12-15 mm.
- The analysis of the product weight according to a screw shape was conducted as follows: the foam agent content was fixed to 2 wt%, and difference in weight between general and foam screws was analyzed using the two-sample t test. Microcellular foaming did not occur in the general screw, since it was a single-spiral shape, and little turbulent flow was generated inside the screw, so that mixing gas and resin did not occur sufficiently.
- The injection speed level was set to 30mm/s, 65mm/s, and 100mm/s, and analyzed using ANOVA. Its P value was 0.
- The current process capability regarding product weight and deformation produced with existing injection molding was analyzed, and the influencing factors were selected on that basis. To evaluate the degree of influence of the factors, analysis on the possible factors was conducted using two-sample t-tests and analysis of variance (ANOVA). In addition, regression analysis method and reaction surface method (RSM) were used to derive the optimized conditions.
- In addition, the following factors related to deformation reduction were selected: screw shape, additive, raw material, injection speed, resin temperature, molding temperature, cooling time, structure of the edge, and heating time of mold-shaped part. To select a vital few factors out of the selected possible factors, two-sample t-tests and ANOVA were used.
성능/효과
- 1. The analysis of possible factors was conducted using two-sample t test and ANOVA, and the results showed that the few vital factors that influenced the product weight were resin temperature and injection speed, and the factors that affected the deformation were width of the edge, resin temperature, and cooling time.
- 2. Regression analysis results verified that the product deformation was minimized when the width of the edge was 12.5 mm.
- 4. The derived optimum conditions were applied to the production process, and the results exhibited that the means and standard deviations of production weight were reduced by 18.6% and 24.2%, respectively, and the process capability was increased from -219.75 to 26.01, indicating significant improvements. In addition, the means and standard deviations of product deformation were also reduced by 71.
- For the additive, analysis was conducted after setting the level to Talc 10%, Talc 15%, and cross-linking agent 2%, but no significant effect on changes in dispersion by the additive type used were found. Thus, the additive was classified as category-type data, and cross-linking agent 2% that displayed the minimum deformation was fixed to the optimum level.
- Based on the result from the experiment design, Pareto chart analysis was conducted according to the structure. The analysis result verified that the interaction of the width and height of the reinforced structure was not significant in terms of the deformation of the product, and that the width had more significant effect on the deformation than the height. Thus, the width was selected as a vital factor that influenced the deformation in the reinforced structure.
- 2(a). The analysis results showed that when the width and height were 3 mm and 0.5 mm, respectively, deformation was the largest as 3.5 mm, and the smallest deformation was changed when the width was 15 mm, regardless of the height. Based on the result from the experiment design, Pareto chart analysis was conducted according to the structure.
- Range of width was selected as 3-15 mm for the optimization of the edge width, and regression analysis was conducted based on the deformation calculated through the computer-aided engineering (CAE) analysis. The analysis results verified that the deformation was reduced as the width increased when the range was 3-12 mm, but the deformation started to increase when the width range was 12-15 mm. Based on this result, regression analysis was conducted.
- 5. The mean and standard deviation of product weight were also reduced, from 1,751.4 g to 1,425 g, and from 1.49 g to 1.13 g, respectively, and the process capability was increased from -219.75 to 26.01, showing a large improvement compared to the existing process.
- Based on this result, regression analysis was conducted. The results determined that the change in deformation in a range of 9-15 mm of width followed the quadratic equation form, and after a certain width, it was ejected before solidification, thereby playing a role in inducing deformation.
- RSM was conducted with regard to the resin temperature and injection speed. The results showed that when the resin temperature was 240.4℃ and the injection speed was 83.2mm/s, 1,426.3g of the minimum product weight could be obtained. The total satisfaction assessment result was 0.
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