When the temperature changes under constant pressure, thermosetting plastics mainly have three material states, namely laminated glass, high elastic state and viscous flow state. At room temperature, plastic is glassy. When the temperature rises to a certain value, the plastic becomes a high elastic condition, and then heated, the plastic becomes a viscous flow condition. Plastic forming production processing (pressing, extrusion, injection, etc.) To be performed under viscous flow conditions. Thermosetting plastics change with the change of temperature. When the temperature drops, the plastic will change from viscous flow condition to high elastic condition, and when the temperature drops to room temperature, the plastic will change to laminated glass condition. In the process of injection molding, the geometric shape and dimensional accuracy of the product can be obtained, which is the characteristics of the thermosetting plastics at various temperatures.
1. Punching and die: punching die is the basic component of the tablet press. Each pair of punching die is composed of three components: upper punching, middle punching and lower punching. The left and right strokes are very similar, and the punch bore is the same. The left and right punch is matched with the die hole of the middle die, and can slide freely left and right in the hole of the middle die, but there is no gap that can leak powder. The production and processing size of the die is the same conventional size, with exchangeability. Die specifications are expressed as punch aperture or middle die aperture, usually 5.5-12mm, one size per 0.5mm, there are 14 specifications.
The punch and die are under great pressure in the pressing link. The common bearing steel is made, and then the heat treatment process is carried out to improve the strength.
There are a wide variety of punches, and the shape of the punch depends on the desired shape of the pill. According to the shape of punch structure, can be divided into round, irregular (including polygon and curve); The shape of punch section includes plane shape, bevel shape, shallow concave shape, deep concave shape and comprehensive shape. Flat and beveled punch are used for flattening cylindrical tablets, shallow concave punch is used for pressing double convex tablets, deep concave punch is mainly used for pressing coated tablet chips, and comprehensive punch is mainly used for pressing special-shaped tablets. For easy identification and medication. Drug name, dosage, vertical and horizontal lines and other marks can also be engraved on the end of the mold. Pressing different doses of tablets, should choose the appropriate size of the die.
