Tablet press machine is mainly used to press powder or granules to tablets of specified diameter, thickness and shape. The machine can be classified to two types, single-punch tablet press and multi-punch (rotary) tablet press.
What does the punch and die include
A single-punch tablet press can have more than one set of punching die but only one set of die would work at most of production time for structure stability and reliability. Furthermore, single-punch tablet press feeds materials and outputs tablets intermittently so that its yield rate is rather low. For this reason, it is mainly used in labs or for large-diameter tablet production. On the other hand, multi-punch rotary table press can runs continuously. Thus it can be applied widely in practical production of food industry, healthcare industry, pharmaceutical industry and so on. In addition, multi-punch tablet press models are variable in punching die number. For example, ZP-35D means the machine has 35 sets of punching dies.
After learning the main differences between the two types of tablet press, we can turn our focus to the critical part of both single-punch tablet press and multi-punch tablet press, i.e., punching die. Punching die is the die for tablet pressing. It’s composed of upper punch, middle punch and lower punch. The punches have similar structure and their punching heads have equal diameter so that the upper and lower punches can slide inside the middle punch freely without powder leakage. The difference is that the upper and lower punches determine tablet shape while the middle punch, tablet diameter. The middle punch can be round or irregular-shaped (polygon or curve), so are the upper and lower punches. Besides, the ends of the upper and lower punches can be flat, sliding, shallow concave, deep concave or synthetical shaped. Flat or sliding punches can be used for flat cylindrical tablets, shallow concave punches for double convex tablets, deep concave punches for tablets to be coated, and synthetical shaped punches for irregular shaped tablets. To make tablet identification and access convenient, drugs name, dosage and special lines can also be embossed on the punches’ ends and then on the tablets. Moderate punching die should be used for different tablets.
Working process of tablet presser
During production, the punches work together to press tablets in the following steps:
1)The lower punching head moves upwards into the middle punch hole and seals up the hole at the bottom.
2)A feeder is used to fill drugs into the middle punch hole.
3)The upper punching head moves downwards into the middle punch hole and press powder or granules into tablets.
4)The upper punching head rises and leaves the middle punch hole while the lower punching head also rises to eject the tablets. In this case, tablet pressing is finished once.
5)The lower punching head exits and is ready for the next tablet pressing.
Dosage control on tablet press machine
Regardless of the seemingly simple working steps, tablet pressing process is comprehensively influenced by two factors, namely, dosage and thickness. Tablets are different in dosage. Major adjustment of dosage can be achieved by different punching head diameter. After punching die specification is determined, the depth of the lower punching head into the middle punch hole can also be adjusted so as to change the actual middle punch hole length after bottom sealing, and finally, for minor dosage adjustment. Therefore, a mechanism for lower punch adjustment should be equipped on the machine for dosage adjustment requirements.
Tablet thickness control on tablet presser
On the other hand, tablet thickness, as well as table appearance, can be influenced by the pressure of tablet pressing which is required to meet storage, transport and disintegration needs. The pressure can be changed by adjusting the downward amount of the upper punching head. Although most of tablet press machines have both downward motion of upper punch and upward motion of lower punch, the pressure is still adjusted and controlled by the structure which controls the downward movement amount of the upper punch.
Single-punch and multi-punch tablet press machines can have similar punching die structure and working steps. But considering their efficiency and cost, single-punch table press can be specially applied in labs, R & D apartment of pharmaceutical enterprises, institutes and so on. But for mass production, we do more recommend the multi-punch tablet press for higher stability and production speed.
