微发泡注塑成型制品表面的螺旋纹及银纹缺陷阻碍了此新工艺的推广应用，此缺陷主要是由填充过程中熔体流动前沿的泡孔发生破裂造成的。为提高微发泡注塑件的表面质量，提出一种利用高压氮气进行加压并使用高压容器进行稳压的模具型腔气体压力控制方法，构建相应的模具型腔气体压力控制装置和控制系统，进行某种医疗器械外观产品的气体反压(Gas counter pressure，GCP)微发泡注塑试验，研究填充过程中模具型腔气体压力对微发泡注塑件表面质量的影响规律。结果表明，随着模具型腔气体压力的提高，微发泡注塑件表面螺旋纹及银纹逐渐减少直至消除，塑件表面光泽度显著提高，塑件表面粗糙度明显降低。对选用的ABS材料，模具型腔气体压力为3 MPa时可获得表面质量优良的微发泡注塑产品。

The application of microcellular injection molding process is severely hindered because of the surface defects such as swirl marks and sliver marks caused by cell rupture of the melt flow front in filling process. In order to improve the surface quality of microcellular injection molding parts, a new method to control mold cavity gas pressure is proposed by using high pressure nitrogen pressurizing and high pressure vessel to ensure the mold cavity gas pressure stable. Corresponding mold cavity gas pressure control device and control system are constructed. Gas counter pressure (GCP) microcellular injection molding experiment of a medical device appearance product is designed to study the influence of GCP on surface quality of microcellular injection molding part. The results show that with the increase of mold cavity gas pressure, the swirl marks and sliver streaks are gradually reduced until be eliminated, the surface gloss of part is greatly improved, and the surface roughness of part is reduced significantly. For the selected material ABS, 3 MPa pressure of mold cavity gas pressure is appropriate to produce the microcellular injection molding part with excellent surface quality.