The capsule manufacturing process is a series of highly controlled steps. It requires utmost precision, given the product’s strict requirements. This guide takes you through the production stages of hard gelatin capsules, which are the most used types.
How are Capsules Made?
Most capsules today are gelatin shells made by immersing metal molds into a gelatin solution. This action coats the molds with a film of the raw material. Upon drying, the film hardens to produce the capsule bodies and caps.
Further steps join the two halves, forming complete structures. Later, the capsules undergo inspections and tests to identify defects before printing and packaging them.
The entire process requires rigorous quality measures. For instance, the manufacturer must ensure correct material formulations. Temperature and humidity or water content levels must also remain within limits.
Hard Vs. Soft Gelatin Capsule Manufacturing Process
Gelatin capsules are of two types: soft encapsulations and hard shells. Hard capsules are two-piece, while soft gel types are one-piece. The two types of capsules differ in their manufacturing steps.
Hard capsules usually come pre-formed and ready for filling. On the other hand, soft gel capsule manufacturing occurs in line. In other words, it combines production steps with the filling process.
With that in mind, our guide will solely focus on making hard capsules. We will also concentrate on the gelatin types. These are the most popular today, with applications in pharma, cosmetics, and other industries.
Capsule Manufacturing Process
We call the manufacturing process of hard gelatin capsules “dip coating.” That’s because it involves lowering molds into a liquid formulation and covering them with a film. The steps below track the key steps from the beginning to the end.
Material Preparation
The raw material is a viscous solution containing 30-40% gelatin in demineralized water. Gelatin is a non-toxic substance obtained from the partial hydrolysis of collagen. The collagen comes from animal skin, tendons, and bones.
- Water mixes with gelatin in pressure tanks.
- The solution gets heated to around 60-70 ° Celsius.
- Vacuum is applied to remove trapped air bubbles.
- The solution goes to the feed tanks.
- Here, it receives pigments, colorants, and other materials.
- Processing aids, such as sodium lauryl sulfate, are also added.
- Adding hot water helps attain the desired viscosity level.
- The correct viscosity helps control capsule thickness and weight.
- From here, the solution moves to the dipping reservoir or pan.
Molding and Drying
Capsule shell molds are stainless steel or manganese bronze pins affixed to metal plates. The pins can produce capsule caps or bodies. Most capsule manufacturing machines have body and cap molds on either side for simultaneous production.
- A set of plates lowers the molds (pins) into the solution.
- Precision mechanisms control the dipping depth and duration.
- The gelatin solution gels on the pins, forming a thin film over them.
- The molds are gradually raised and rotated.
- The rotation distributes the gelatin evenly, ensuring its uniform thickness.
- It also prevents beads from forming at the body and cap ends.
- In the next step, air blow dries the film, setting it.
- Further drying in successive ovens removes specified amounts of water or moisture.
Stripping and Trimming
The gelatin film is not set over the molds and is ready for removal. This process occurs in the stripping and trimming stations with the help of bronze jaws and straight knives.
- Automated jaws remove the formed gelatin from the molds (pins).
- The jaws ensure the correct body and cap length for consistency.
- Stripped shells go to the collets for trimming.
- As the collets spin, sharp knives cut the shells at specific locations.
- Trimming reduces the lengths to ensure proper size and uniformity.
- Waste from the cutting leaves the production line for recycling.
Joining and Polishing
With the capsule caps and bodies stripped and trimmed to size, they are now ready for locking. This processing step prepares them for polishing, inspection, testing, printing, etc.
- The separate bodies and caps are aligned and gently pushed together.
- The now complete capsules undergo polishing.
- Polishing methods include pan, brushing, and cloth.
- Polishing removes dust and any other materials.
- Meanwhile, another process cleans the pins, prepping them for another cycle.
- They also receive a release agent coating.
Inspection and Sorting
Joined capsules must undergo manual or automated inspection to identify manufacturing errors. They also require sorting to separate defective pieces from the production line.
- The capsules pass on an illuminated inspection line.
- Workers identify and remove defective pieces.
- Inspection can also involve high-resolution cameras and computers.
- The capsules may undergo further moisture removal to attain the desired limits.
Testing and Printing
Various tests characterize the entire capsule manufacturing process. After-production testing is necessary to ensure the final product meets desired quality standards. On the other hand, printing serves branding and identification functions.
- The locked capsules undergo various tests to check their size, color, and moisture content.
- Later, a rotary component prints the required information on the capsule.
- The information can include product name and company name or logo.
- Capsules for holding medicines require edible ink printing for safety.
Packaging and Storage
The above process manufactures empty capsules. Sometimes, the capsule manufacturer fills them. Most often, the producing company sends the capsules to clients for filling.
- Completed capsules go into moisture-proof packaging materials.
- The manufacturer may then store or ship them to various destinations.
- The capsules may require filling with a drug substance like an antibiotic.
- The contents can also be an industrial product or agricultural chemical.
- Filled capsules are ready for consumers to use.
Common Capsule Manufacturing Defects
Like any other industrial process, the capsule manufacturing process is prone to errors. These occur during production steps due to machine or operator errors. Some are storage-related and caused by environmental factors.
Color Defects
- Color variations – causes include unstable dyes and colorants or incorrect formulations
- Discolorations – these may result from exposure to light, heat, or microbial contamination
Shape and Size Problems
- Short body/caps – the shells are too wet or incorrectly held in the collets
- Long body/caps – broken trimming knives or their absence
- Double cap – locking errors
- Wall too thick/thin – uneven gelatin distribution caused by incorrect solution viscosity or reduced wetting or gelling agents
Physical Damage
- Imperfect/rough cuts – blunt trimming knives
- Splits – low moisture levels or lack of inadequate plasticizer amounts
- Holes/scratches – cap and body stripper impact due to incorrect machine setting
- Spots/specks – pigment hominization problems or the presence of foreign materials
- Bubbles – improper vacuuming leaving bubbles in the solution
Printing Errors
- Incorrect print position – uneven ink flow and calibration errors
- Blurred print – ink adhesion and drying issues or improper blends
- Repeat printing – printing system errors or machine malfunctions
- Lack of print – ink delivery and adhesion problems
Conclusion
Capsule manufacturing is a delicate process that requires extensive control steps. More importantly, you need the right machine to ensure that shells form correctly. Correct machine settings also help avoid errors, whether manufacturing hard or soft gelatin capsules. We hope this write-up has helped you understand the process in more detail.
