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Problems and solution in tablet pressing

May 10, 2022

During tablet pressing production on tablet press machine, there may be some problem occurs during the production, now let’s see what are the most common problems and solution in tablet pressing production.

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1. Incompact tablets
1) Problems: Sometimes, compressed tablets are not hard and have small holes. They can be scattered when pressed slightly.
2) Analysis and solutions
a. The drug powder is not fine or not uniformly mixed due to high content of oily ingredients. Operators can sieve the powder though 100-mesh screen, mix it with viscose adhesive, increase tablet compressing pressure and add absorbent for uniform mixing.
b. Improper dosage or type of adhesive and moisturizer will also lead to fragility, non-uniform fineness and even stratification of granules. Operators should determine the proper adhesive type and dosage, improve granulation techniques and mix material completely.
c. Some granules contains little moisture. Dry granules are pretty elastic and the material will lose its crystal water, so that the granules will be fragile and furthermore the tablets become fragile. Therefore, during granulation, the water content of granules should be strictly controlled. If the granules are too dry, some thin alcohol (50-60%) can be mixed with them before tablet compressing.
d. Drug property will also have influence on the hardness of tablets. Tablets compressed from high-density material, although are of certain hardness, cannot be impacted. For example, Bismuth Subnitrate Tablets or soda tablets are usually fragile. But if material is of low density, poor fluidity and compressibilty, operators need to granulate them again.
e. Sometimes granules are of poor fluidity, which leads to non-uniform distribution of granules filled in the compressing mold.
f. Large lumps or granules will block the feeder or granule scraper, which influences the filling volume.
g. Factors of compressing machine can also be influential, including low pressure, puncher in different length, high operation speed or unstable volume of granules in the hopper. To solve this problem, operators can adjust the pressure, standardize the punching mold, control production speed and stabilize the material volume.


2. Tablet breaking
1) Problems: When tablets are shaken, some of them breaks at the center or at the top. The former is called center-breaking, the latter top-breaking and both of them are generalized as tablet breaking.
2) Analysis and solutions
a. Some drugs are elastic or contain much fibrous or oily ingredients. Operators can feed sugar powder to weaken fiber elasticity and strengthen adhesion, or absorbent for the oily ingredients before complete mixing and tablet compressing.
b. Adhesive or moisturizer are not used in proper type or dosage, which lead to poor adhesion of granules during tablet pressing.
c. Some granules are dry and lose too much crystal water. The solution is the same with that for fragile tablets.
d. Some crystal drugs are not ground completely before granulation.
e. Tablet breaking can also be caused by too much fine powder or excessive dosage of lubricant. The air in the powder is not exhausted timely but compressed into the tablets. When compression finishes, the air inside tablets expand so that tablets break. This problem can be solve by screening out fine powder and reduce dosage of lubricant.
f. Large compressing pressure will have large rebound pressure, which lead to tablet breaking, too. High production speed or undesirable punchers that have different length, are worn at the center, have wider central part or that curl inward can also lead to tablet breaking when tablets are punched out. Operators can control the pressure and production speed and better and change the punching mold.
g. Low temperature and humidity will also cause tablet breaking, especially for those drugs of poor viscosity. Operators can adjust the air-condition system to solve this problem.

3. Material sicking to the punch and die
1) Problems: During compressing, fine powder on the surface of tablet sticks to the puncher or the punching mold. As a result, tablets are not smooth or even. The powder sticks more easily to the lettered punching mold.
2) Analysis and solutions
a. Granules contain too much moisture, drugs are easy to be dampened or the temperature and humidity are too high. In this case, please dry granules, and control temperature and humidity in the production room to avoid dampening.
b. Lubricant is used in small dosage or material is not mixed uniformly. Operators can add lubricant moderately and mix the material completely to solve the problem of punch sticking.
c. Unclean puncher, anti-corrosive or lubricating oil on the puncher, rough surface of new punching mold or edges and corners of the letters can also be influential. Clean the puncher, change the unstandard mold or lubricate the letters with liquid paraffin to solve these problems. Besides, mechanical heating can also cause material to stick to the puncher. In this case, check and maintain the machine.

4. Tablet weight error over the limit
1) Problems: Tablets weight difference is beyond the limitation.
2) Analysis and solutions
a. Granules are of different size and different flowing rate during compression. If it contains more coarse granules, a tablet will be light and vice verse. In this case, the operators should screen out some fine powder. If this solution is not feasible, granulate them again.
b. Fine powder’s sticking to the puncher can also lead to large tablet weight difference. Operators should check the puncher timely and clean it to solve this problem.
c. The problem can also be caused because granules don’t flow well and granules flowing in the mold hole is sometime heavy and sometimes light. The granules should be granulated again or glidant such as powdery silicon can be fed to better granules’ fluidity.
d. The feeder might be clogged. This phenomenon often occurs when drugs are too viscose or sensitive to moisture. Operators can clean the feeder timely, keeps tablets being compressed in a dry condition and feed some glidant.
e. The puncher doesn’t match the mold hole well. For example, some drug powder leaks around the puncher, which hinders the puncher’s motion and reduce filling volume. To solve this problem,. the puncher and mold ring should be changed.
f. High production speed lead to smaller filling volume than the required.
g. Punchers have different length and material cannot be filled in the same volume.
h. Distributor are not well installed, which cause unstandard material filling.


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