Research On The Process Optimization Of Bottom-up Projection Based Mask Projection Stereolithography

Light-cured 3D printing is an important one in 3D printing technology,including point forming process(SLA)and mask projection stereolithography(DLP,LCD).Its development is earlier,commercialization is more mature,and there are many practical applications.Mask projection stereolithography,especially DLP 3D printing technology,has occupied many markets due to its high molding precision,high printing efficiency and low equipment cost.It has many applications in jewelry,medical and aerospace.However,the mask projection stereolithography still has some process limitations.For example,the resolution limits the printing accuracy and printing size,and the separation of large-sized solidified layers is difficult.In this paper,the process optimization research is carried out for these two process limitations.The main research contents are as follows:(1)The prototype of the pixel offset method was built independently.By adding micron-scale offset motion to the projection module and projecting the images of different effective pixel distributions before and after the offset,the sub-pixel level printing accuracy under the single projection module was realized.The printing process of pixel offset method is designed.The pixel-shifted gray image algorithm based on area weighting is proposed.According to the average gray level of the image contour,the distribution of exposure time of two pictures is planned.The effectiveness of the pixel offset method and the related image algorithm is verified by experiments,and the necessity of the exposure time allocated by the pixel offset image according to the validity is verified.The experimental results show that the pixel offset method is effective,and the area-weighted pixel offset gray image algorithm significantly improves the printing accuracy.(2)By adding texture lines to the large-area solidified layer,the stability of the printing separation process is greatly improved,the separation force which may occur during the separation process is obviously suppressed,and the printing forming stability is improved.By real-time monitoring of the separation force in the printing process,combined with the positive correlation between the separation force and the printing area,the separation force threshold is demarcated,the model is broken or dropped,and the automatic shutdown alarm is realized in the case of printing failure.