The working principle of tablet press
Punches and dies are under a lot of pressure during the tableting process. They are usually made of bearing steel and heat-treated to increase their hardness.
There are many types of punches, and the shape of the punch depends on the desired shape of the tablet. According to the shape of the die structure, it can be divided into circular and special-shaped (including polygonal and curved); the shape of the punch section is flat, hypotenuse, shallow concave, deep concave and comprehensive. Plane and hypotenuse punches are used for pressing flat cylindrical tablets, shallow concave punches are used for pressing biconvex tablets, deep concave punches are mainly used for pressing the core of coated tablets, and composite punches are mainly used for pressing Shaped sheet. In order to facilitate the identification and taking of medicines, the name of the medicine, dosage and vertical and horizontal lines can also be engraved on the end face of the die. To compress tablets of different doses, dies of suitable size should be selected.
Working process of the tablet press
The working process of the tablet press can be divided into the following steps:
① The punch part of the lower punch (its working position is upward) extends from the lower end of the middle die hole into the middle die hole to seal the bottom of the middle die hole;
②Use a feeder to fill the drug into the die hole;
③The punch part of the upper punch (its working position is facing downward) falls from the upper end of the middle die hole into the middle die hole, and goes down a certain stroke to press the powder into tablets;
④The upper punch is lifted out of the hole, and the lower punch is lifted to push the tablet out of the die hole, completing a tablet pressing process;
⑤ Lower the punch to the original position, ready for the next filling.
Principle of tablet press machine
① Dose control. Various tablets have different dosage requirements, and large dosage adjustment is realized by selecting dies with different punch diameters, such as punches with diameters of 6mm, 8mm, 11.5mm, and 12mm. After the die size is selected, the tiny dose adjustment is to adjust the depth of the lower punch into the middle die hole, thereby changing the actual length of the middle die hole after the back cover, and adjusting the filling volume of the drug in the die hole. Therefore, the tablet press should have a mechanism to adjust the original position of the lower punch in the die hole to meet the dosage adjustment requirements. Since there is always a difference in specific volume in the preparation of different batches of powder, this adjustment function is very necessary.
In dosage control, the action principle of the feeder also has a considerable influence. For example, when the granular medicine is freely rolled into the hole of the die by its own weight, its filling condition is relatively loose. If multiple forced entry methods are used, more medicine will be filled in the die holes, and the filling situation will be relatively dense.
②Control of tablet thickness and compaction degree. The dose of the drug is determined according to the prescription and pharmacopoeia and cannot be changed. For storage, storage and disintegration time limit requirements, a certain dose of pressure is also required during tablet compression, which will also affect the actual thickness and appearance of the tablet. Pressure regulation during tablet compression is essential. This is achieved by adjusting the downward movement of the upper punch in the die hole. Some tablet presses not only have the upward and downward movements during the tablet pressing process, but also have the upward and downward movements of the lower punch, and the tablet pressing process is completed by the relative movement of the upper and lower punches. However, pressure regulation is mostly achieved by adjusting the mechanism of the upstroke and downstroke.