Common Issues and Discussions on Rotary Tablet Press machine
Common Issues and Discussions on Rotary Tablet Press machine
A rotary tablet press machine is a type of mechanical equipment used in industries such as pharmaceuticals, food, and chemicals, primarily for compressing powdered or granular materials into tablets. However, during practical application, the tableting process often encounters common issues such as weight variation, powder leakage, and noise. Therefore, this article analyzes the common problems of rotary tablet press machine and proposes corresponding solutions to provide theoretical guidance for the production process.
Tablet press machine is one of the commonly used device in the pharmaceutical industry, employed to compress drug powders or granules into various types of tablets, such as vitamin tablets, antibiotic tablets, and pain relief tablets. Based on their characteristics and functions, tablet press machine can be categorized into single-punch tablet press machine, multi-punch tablet press machine, double-layer tablet press machine, rotary tablet press machine, and other types. Among these, rotary tablet press machine is known for its high production efficiency and continuous operation, making it suitable for large-scale industrial production and thus widely used in pharmaceutical manufacturing activities.
The initial definition of domestic high-speed rotary tablet press machine was that the linear speed of the center hole of the middle die should not be less than 60 m/min. With the continuous expansion of the pharmaceutical tablet market, advancements in tableting process technology and control technology, and the increasing quality requirements for tableting under GMP certification, rotary tablet press machine have gradually become a symbol of high performance and high efficiency [1]. However, during production and use, operators often encounter a series of common issues that may negatively impact granule quality and production efficiency. To help manufacturers better understand and address these problems, this article explores the common issues of rotary tablet press and corresponding countermeasures.
Part 01: Working Principle of Rotary Tablet Press machine
The working process of a rotary tablet press machine is a continuous cycle. This cycle includes the feeding zone, compression zone and residual material recovery and dedusting zone. Each zone has its specific function, and through the continuous action of these zones, the material is ultimately compressed into tablets, as shown in Figure 1.
Figure 1: Simplified Diagram of the Working Process of a Rotary Tablet Press machine
Feeding Zone: The main function of the feeding zone is to evenly distribute the powder into the die holes, ensuring a consistent amount of material for each tableting cycle. This process is typically accomplished by a feeder or scraper, as shown in Figure 2.
Figure 2: Crescent-Shaped Feed Frame (Front View on Left, Rear View on Right), with Scraper Plates on Both Sides
Compression Zone: The material enters the main compression zone. This zone has a pair of main compression rollers, where the upper and lower punches move closer together under the action of the main compression rollers, applying greater pressure to the material to finally form it into a tablet. The upper punch, middle die, and lower punch are shown in Figure 3.
Figure 3: Left: Upper Punch, Middle: Lower Punch， Right: Middle Die
Residual Material Recovery and Dedusting Zone: During the tableting process, some powder or fragments may remain around the die. The function of this zone is to clear these residues, maintain cleanliness in the tableting area, and recycle the recovered residual material. This process is typically accomplished through vacuum suction or other dedusting equipment.
After passing through the feeding zone, main compression zone and residual material recovery and dedusting zone, a cycle is completed to compress the material into tablets. Continuous tableting is the repetition of this cycle.
Part 02: Common Issues with Rotary Tablet Press machine
During the use of rotary tablet press machine, various issues may arise that affect production efficiency and tablet quality. Below are some common problems and their potential causes.
2.1 Powder Leakage Phenomenon
Definition of Powder Leakage: For a material with mass M1, the mass of the tablets produced (including both qualified and non-qualified tablets) is M2. The mass difference M0 = M1 - M2 is the amount of powder leakage [1]. Severe powder leakage can lead to material waste and contamination of the working environment.
There are many causes of powder leakage, as detailed below:
Issues with the Feeding System: Poor sealing performance of the feeding system, excessive feeding speed, or an unreasonable feeder design can lead to powder leakage during the feeding process.
Poor Scraping Effect: If the scraper on the crescent-shaped feed frame fails to promptly recycle the residual material from the accumulation tank back into the feeder, the residual material will accumulate and eventually be thrown out as the middle turret rotates, resulting in powder leakage, as shown in Figure 4.
Figure 4: Powder Leakage Phenomenon
Poor Die Sealing: Excessive clearance between the upper punch, lower punch, and die hole, die wear, or improper installation can affect sealing performance, leading to powder leakage.
Excessive Vibration of the Tablet Press: Vibration generated during machine operation can cause powder leakage.
Poor Material Flowability: If the material has poor flowability or uneven particle size distribution, it is prone to scatter during feeding and tableting, increasing the likelihood of powder leakage.
2.2 Tablet Weight Variation Issues
Tablet weight variation in rotary tablet press machine can be caused by various factors, as listed below:
Material Characteristics: For example, if the material's humidity is too high or too low, it affects its flowability, leading to uneven feeding and consequently uneven tablet weight.
Large Density Differences in the Material: This can cause stratification during feeding, resulting in uneven feeding.
Powder Leakage: Leakage and scattering of powder can lead to uneven filling of the die holes, affecting the weight and content consistency of the tablets.
Severe Die Wear: Prolonged use can cause die wear, surface damage, or deformation, affecting material filling and compression effectiveness, leading to uneven material filling.
Uneven Tableting Pressure: Uneven pressure between the upper and lower punches can cause weight variation in the tablets.
2.3 Physical Quality Issues of Tablets
Physical quality issues of tablets are also critical during the entire production process. These issues primarily affect the appearance, mechanical strength, and disintegration performance of the tablets. Common physical quality issues include insufficient or excessive tablet hardness, rough tablet surfaces, and tablet breakage or cracking. The main factors affecting tablet quality include improper pressure settings, unsuitable material moisture content, uneven particle size distribution, and poor material flowability. Additionally, checking whether the die design is reasonable, whether the die surface is rough or contaminated, and whether it is damaged will also help identify causes of physical quality issues.
2.4 Noise and Vibration Issues
Any rotating machinery inevitably generates vibration and noise during operation. Rotary tablet presses also exhibit noticeable noise and vibration during use. The noise primarily originates from components such as the main motor, main transmission worm gearbox, main shaft, and punch turret . For example, low precision of the main motor bearings or excessive bearing clearance can cause increased vibration and noise in the rotary tablet press. Wear of the worm and worm gear in the main transmission worm gearbox, poor meshing, bearing wear or failure, and poor lubrication can also lead to this phenomenon. Imbalance due to uneven mass distribution during the manufacturing of the punch turret or damage during use, as well as coaxiality errors in the upper, middle, and lower punch holes of the turret causing uneven force on the punches during tableting, can also trigger vibration and noise.
2.5 Other Issues
In addition to the above issues, other problems may occur, such as feeding system blockages, uneven discharge, and uneven tablet color. Only by understanding the underlying causes can these problems be better resolved, thereby producing higher-quality products.
Part 03: Countermeasures for Common Issues
3.1 Countermeasures for Powder Leakage Phenomenon
For the powder leakage phenomenon, the following measures are primarily adopted:
Improve the Structure of the Dedusting Mechanism: Install a dedusting blade or scraper on the crescent-shaped feed frame, as shown in Figure 5. Regularly inspect the dedusting effect of the blade or scraper and replace it periodically.
Figure 5: Working State of the Punch Die and Scraper Plate in the Crescent-Shaped Feed Frame
Select Appropriate Raw Materials: Choose powdered raw materials with good flowability and uniform particle size to reduce dust generation.
Improve the Sealing of the Tablet Press: Enhance the sealing of the tableting area and the powder conveying system. Adjust die clearances to ensure proper alignment between the upper and lower punches. Regularly inspect the wear of punches and dies, and replace severely worn parts promptly to ensure smooth die surfaces and minimize powder leakage.
Use an Efficient Dust Removal System: Install suction devices at key positions of the tablet press to promptly remove leaked powder, maintaining the cleanliness of the equipment and working environment.
3.2 Countermeasures for Tablet Weight Issues
Addressing tablet weight variation requires comprehensive consideration and optimization of equipment, processes, raw materials, and operations.
Improve the Feeding System: Regularly inspect the feed hopper, feeder, and conveying pipelines to ensure there are no blockages or powder residues. Ensure the feeding system provides a uniform and stable supply of materials. Utilize an automated feeding system to enhance uniformity and consistency.
Adjust Die Clearances: Regularly check and replace damaged dies to ensure proper alignment between the upper and lower punches, consistent aperture sizes, and uniform clearances to prevent powder leakage.
3.3 Countermeasures for Physical Quality Issues of Tablets
To address physical quality issues in tablets:
Improve Material Flowability: Control material humidity, viscosity, and particle size. Avoid overly wet or dry conditions, as they can cause sticking or cracking.
Adjust Pressure Settings: Optimize the pressure between the upper and lower punches by setting appropriate pressure parameters. Excessive or insufficient pressure can lead to tablets that are too hard or too soft.
Inspect Die Surfaces: Ensure die surfaces are smooth and free from wear, as this significantly impacts tablet quality.
Use Lubricants Appropriately: Regularly clean and polish dies, and replace damaged ones promptly to reduce physical quality issues.
3.4 Countermeasures for Noise and Vibration Issues
Noise and vibration are inevitable in machinery, but optimizing these issues can extend equipment lifespan, improve operator comfort, and enhance tablet quality.
Optimize Main Motor Usage: The ideal frequency for the main motor is at the industrial frequency. If it frequently deviates significantly, a variable-frequency motor is recommended.
Regularly Inspect Worm Gears and Worm Screws: Check for wear and lubrication, ensuring sufficient and high-quality lubricant to reduce friction and noise.
Maintain Bearings: Regularly inspect and replace worn or faulty bearings. Use high-quality bearings with proper lubrication to minimize noise and vibration.
Ensure Punch Turret Quality: Use high-precision, high-quality punch turrets. Ensure proper installation, smooth surfaces, and required precision. Check the alignment between the punch turret and dies to ensure appropriate clearances, as shown in Figure 6, and lubricate if necessary. Balance calibrate the punch turret to ensure smooth rotation and reduce noise and vibration.
Figure 6: Comparison Before and After Die Installation
3.5 Employee Training and Standardized Operations
Employee training and standardized operations are crucial for the use of any industrial equipment, especially for complex and precision devices like rotary tablet presses.
Train Employees: Equip them to identify and address potential safety hazards. Teach them how to set and adjust equipment parameters, such as pressure, rotation speed, and filling volume, to ensure product quality and production efficiency.
Establish a Production Recording System: Maintain detailed records of production parameters, equipment status, and operator information for each batch to enable traceability and quality control.
Perform Regular Maintenance: Conduct routine lubrication and cleaning to prevent dust and impurities from damaging the equipment and ensure smooth operation.
Part 04: Conclusion
With the advancement of Industry 4.0 and smart manufacturing, rotary tablet press machine will increasingly integrate automation and intelligent technologies. For example, advanced sensors and control systems can monitor key parameters in real time during production, improving efficiency and product quality.
Additionally, as the global population ages and the prevalence of chronic diseases rises, the demand for efficient and safe medications continues to grow. This will drive the widespread application of rotary tablet presses in the pharmaceutical industry to meet the need for large-scale production of high-quality tablets.
Beyond the traditional pharmaceutical sector, the use of rotary tablet press machine in the nutraceutical and health supplement markets is also expanding. With increasing health awareness, the demand for vitamins, minerals, and other nutritional supplements will continue to rise, creating new market opportunities for tablet press machine.
Furthermore, as globalization progresses, pharmaceutical companies in different regions will face intensifying international competition. To secure a place in the global market, rotary tablet press manufacturers must adhere to international standards, such as GMP (Good Manufacturing Practices) and FDA (U.S. Food and Drug Administration) regulations, ensuring compliance with various national laws and quality requirements.
In summary, the future of rotary tablet press machine is filled with opportunities and challenges. Through continuous technological innovation and market expansion, these devices will play an increasingly important role in pharmaceuticals, nutraceuticals, health supplements, and other fields.
Shanghai Tianfeng Pharmaceutical Equipment Co., Ltd.
No.8 tianfeng road,Songjiang Zone,Shanghai,China
Phone: 86-13524985109
WhatsApp: 86-13524985109
WeChat: 13524985109
Skype: 86-13524985109
Web: www.pilltabletpressmachine.com
E-mail: chenyang@shtf.cn
