Introduction of ceramic injection molding process
The ceramic injection molding process mainly includes four processes: feeding, injection molding, degreasing and sintering.
1. Selection and optimization of powder
As the main material for injection molding, the most important requirements are fine particle size and regular shape. Powder with small particle size has good fluidity during injection molding, large filling amount, and low sintering shrinkage.
- Adhesive selection
The selection of binder system is the core link of alumina ceramic injection molding. It not only directly affects the injection performance of the feed, but also determines the degreasing method and affects the final performance of the product. The binder system has two basic functions in the injection molding process: first, to ensure that the feed has good fluidity; second, to ensure the strength of the green body.
Currently, the most commonly used binders for alumina ceramic injection molding consist of paraffin wax (PW), polypropylene (PP) and stearic acid (SA).
- The effect of surfactants
According to rheological theory, surfactants control the properties of ceramic feeds to a large extent, and the stability of feeds increases with the increase of the adsorption layer on the surface of ceramic particles. In the injection molding process of alumina ceramics, the amount of surfactant will vary with other components of the binder, and its content is mostly between 1% and 5%.
The degreasing process is the longest time-consuming process in the injection molding process and the most critical process for quality control. Improper degreasing can lead to many product defects. A lot of research work has shown that the degreasing process is inseparable from the addition of binders, and different binders use different degreasing methods.
The degreased ceramic green body is a low density porous molded body. It requires densification and sintering at high temperatures to obtain dense ceramic parts with the required dimensional accuracy and fiber structure.