How To Solve The Problem of Mold Punch Adhesion During Tablet Making Production?

Mold punch adhesion refers to the phenomenon where a thin layer or a small portion of the tablet's surface is stuck to the punch of mold, resulting in rough and uneven surface or dents on the tablets. Here are some solutions to solve the problem of mold punch adhesion in tablet production:

1. Improving powder material factors

A. Controlling powder material moisture

More materials are hygroscopic, and when the ambient humidity is high or the material itself contains too much moisture, then easily sticking to the punch. For example, materials containing lactose, starch, etc., may stick to the punch if the moisture content exceeds a certain limit during tablet pressing. Therefore, for materials that are easily hygroscopic, their moisture content should be strictly controlled, which can generally be achieved through drying treatment, such as drying at a suitable temperature and time, like drying materials in an oven at 50-60℃, to control the moisture content within a suitable range, such as 1%-3% (the specific value varies depending on the material).

Regarding the production environment, it is important to control the relative humidity in the production workshop. Dehumidifying equipment can be installed to keep the relative humidity in the workshop within the range of 40%-60% to reduce the possibility of materials absorbing moisture.

B. Optimizing the particle size and distribution of materials

The particle size and distribution of materials also affect punch sticking. If the particle size of the material is uneven and there is too much fine powder, these fine powder is easily to fill between the punch and the die orifice during tablet pressing, increasing the risk of punch sticking. For example, for some traditional Chinese medicine powder tablets, if they have not been properly pulverized and screened, the particle size difference of the powder is large, and the fine powder may adhere to the surface of the punch.

The solution is to crush and screen the material to achieve a more uniform particle size distribution. Multi-level screening equipment is typically used, such as first using a coarse sieve to remove larger particles, and then using a fine sieve (e.g., an 80-100 mesh sieve) to screen out materials with a suitable particle size range, reducing the proportion of fine powder. Simultaneously, flow aids, such as micronized silica gel, can be added, which improves the flowability of the material and prevents fine powder aggregation; the typical addition amount is 0.1%-0.5%.

C. Adjusting powder material formulation

Some material components may interact to lead to sticking. For example, in some compound tablets, chemical reactions or physical adsorption may occur between the drug component and excipients. If the active pharmaceutical ingredient is a viscous extract, mixing it with certain excipients may increase viscosity.

2. Optimizing tablet press and process parameters

A. Cleaning and maintaining punches and dies

During the tablet pressing process, material may remain on the surfaces of the punches and dies. If not cleaned promptly, this residue will gradually accumulate, increasing the probability of punch sticking. For example, after continuous tablet pressing, some sticky components may adhere to the punches and transfer to the surface of new tablets during the next tablet pressing cycle.

Therefore, the punch and die should be cleaned regularly by a suitable cleaning agent, such as a dedicated die cleaner, and gently wipe the surface of the punch and die with a soft cloth or brush to remove any residual material. At the same time, checking the surface of the punch and die for damage such as scratches or dents, as these defects can make material adhere more easily. Damaged punches and dies should be replaced or repaired promptly.

B. Adjusting tablet pressing pressure and speed

Excessive pressing pressure causes the material to be squeezed too tightly, then potentially overflowing from the die edge and sticking to the punch. For example, for tablets requiring high hardness, improper pressure settings can easily lead to punch sticking. Similarly, excessively fast compressing speed prevents the material from distributing evenly within the die, also causing punch sticking.

The tablet pressing pressure and speed can be optimized through more testing. Generally, starting with lower pressure and speed, gradually increasing the pressure while observing the tablet quality to find the optimal pressure range that ensures acceptable tablet hardness and appearance without sticking. The tablet pressing speed can usually be adjusted based on the material properties and equipment performance, such as reducing the speed from a high 100 tablets per minute to 60-80 tablets per minute.

C. Controlling tablet temperature

During tablet pressing, the tablet temperature may rise due to factors such as friction. If the temperature is too high, the viscosity of the material may increase, leading to sticking. For example, some heat-melting materials become more viscous when the temperature rises.

It’s available to control the tablet temperature by some solutions: on one hand, cooling devices, such as air-cooled or water-cooled systems, can be installed on tablet press machine to cool the tablets during the compression process; on the other hand, the tablet pressing process can be optimized to reduce unnecessary friction, for example, by properly lubricating the punches and die orifices to reduce the heat generated by friction.

If you have any questions about the machine production process or don't know how to operate the machine, please feel free to contact us.