Cratering in Tablet Coating
What is the description of the problem?
The presence of pits and irregularities at the top of the tablets surface due to the increased porosity of the tablets surface and the penetration of the coating solution into it.
What are the reasons? Are the reasons related only to the coating stage or are there other reasons?
Firstly, reasons related to the granulation stage:
1: The time for the blending process is insufficient.
2: The granulation time is short.
3: The amount of binder is insufficient.
4: The presence of a very high percentage of highly soluble substances.
5: The percentage of lubricant is low.
Solutions:
1: Blending properly.
2: Increase the granulation time.
3: Increase the amount of binder or change its type.
4: Reducing the percentage of highly soluble substances.
5: Increase the percentage of lubricant.
Secondly, reasons related to the Compression stage:
1: low hardness of the tablets.
2: The machine speed is very high during pressing.
3: The presence of high differences in weights (wight variation)..
4: The design of the punch is very poor.
Solutions:
1: Increase the hardness of the tablets .
2: Reduce the machine speed.
3: Reducing the variation between the weights of the tablets.
4: Choose a suitable design for punches
Thirdly, reasons related to the COATING stage
1: Improper drying and low inlet air flow.
The solution: Increase the amount of inlet air flow.
2: The temperature of the tablets is very low.
The solution: Increase the temperature of the tablets.
3: Improper loading of tablets into the drum.
The solution: Therefore, please do not turn on the pan during the charging process.
4: Heating at high pan speed (high drum speed during preheating).
The solution: Reduce the pan speed during preheating.
5: Start spraying at a high spray rate.
The solution: Reduce the spray rate at first.
6: A solution with very low viscosity
The solution: Increase the viscosity of the solution.
7: Use too little atomizing air, which leads to overwetting and the tablets sticking to the drum body.
The solution: Increase atomizing air.
8: The distance between the guns and the tablets is very close (guns to tablets bed too close).
The solution: Increase the distance between the guns and the tablets.
9: Poor performance of the guns , which leads to a variation between one gun and the other.
The solution: maintenance of the guns .
10: Improper spray angle, which makes the tablets drying time shorter after the tablets meet with the spray and return again in front of the guns.
The solution: Work at an suitable spray angle.
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