Recent progress in minimizing the warpage and shrinkage deformations by the optimization of process parameters in plastic injection molding: a review.

The quality control of plastic products is an essential aspect of the plastic injection molding (PIM) process. However, the warpage and shrinkage deformations continue to exist because the PIM process is easily interfered with by several related or independent process parameters. Thus, great efforts have been devoted to optimizing process parameters to minimize the warpage and shrinkage deformations of products during the last decades. In this review, we begin by introducing the manufacturing process in PIM and the cause of warpage and shrinkage deformations, followed by the mechanism about how process parameters, like mold temperature, melt temperature, injection rate, injection pressure, holding pressure, holding and cooling duration, affect those defects. Then, we summarize the recent progress of the design of experiments and four advanced methods (artificial neural networks, genetic algorithm, response surface methodology, and Kriging model) on optimizing process parameters to minimize the warpage and shrinkage deformations. In the end, future perspectives of quality control in injection molding machines are discussed.

[Comparison of the incidence rates of anastomotic leak following lower anterior resection of rectal cancer between laparoscopic and open operation].

OBJECTIVE: To investigate and compare the incidence rates of postoperative anastomotic leak following laparoscopic (LP) versus open (OP) lower anterior resection for rectal cancer. METHODS: Fifty-three cases of LP and 135 cases of OP lower anterior resection with rectal cancer site 5-8 cm away from anal edge were operated by the same surgeon team from Sep. 2000 to Dec. 2005. The differences of postoperative anastomotic leak of protective stomy and non-protective stomy between LP and OP groups were analysed. RESULTS: In LP group, the incidence rates of the postoperative anastomotic leak of protective stomy and non-protective stomy were 4.6% (1/22) and 6.5% (2/31) respectively (P>0.05, chi(2)=0.088). In OP group, the incidence rates were 2.3% (1/43) and 8.7% (8/92) respectively (P>0.05, chi(2)=1.024). No significant difference existed between LP and OP groups with protective stomy (P=0.455), neither did LP and OP groups without protective stomy (P=0.288). CONCLUSION: Laparoscopic low anterior resection of rectal cancer is a safe procedure. It doesn't increase the incidence rate of anastomotic leak as compared to traditional open surgery.