A wide array of tablet defects can arise during tablet manufacturing and tablet coating, compromising pill quality and drug efficacy. Common issues such as capping, cracking, chipping, and sticking/picking present challenges for tablet manufacturers. For better eliminating defects in tablets, we explore root causes of these frequent tableting deffects and provide practical solutions to handle and prevent defective tablets, ensuring a robust tablet manufacturing process.
This category of tablet defect directly affects the appearance of drug tablets, patient medication experience, and image of pharmaceutical manufacturers. Root causes of these tablet defects are often related to granule properties (moisture content, cohesive strength, granule flowability), equipment parameters (pill press pressure, tablet pressing speed, tablet presser tooling condition), and environmental conditions (humidity, temperature).
In actual tablet manufacturing, it is necessary to follow the process of "troubleshooting tablet granules → adjusting pill presses → controlling tablet pressing environment" to handle specific defects of tablets and let quality of medication tablets meet tablet production standards. In the following paragraphs, we will indicate 5 main tablet defects in tablet manufacturing.
|
Defect Type |
Appearance Characteristics |
Occurrence Location |
Common Causes |
|
Cracking |
Fine linear cracks (no material loss) |
Surface or internal |
Insufficient binder, overly dry granules |
|
Capping |
Top/bottom annular layer separation |
Upper/lower punch contact surface |
High granule elasticity, excessive main compression force |
|
Chipping |
Edge chipping / burrs (small fragments broken off) |
Tablet edges |
Worn die bores, poor granule flowability |
|
Sticking |
Rough, sticky surface with powder adhering to punches |
Entire surface |
High moisture content, low punch smoothness |
|
Picking |
Surface defects/holes corresponding to punch engravings |
Punch engraving, recess area |
Punch recess, excessive fine powder |
|
Flaking |
Flaky surface layer peeling |
Random surface areas |
Uneven binder distribution, insufficient pre-compression |
Tablet cracking refers to the appearance of irregular fine cracks inside or on the surface of a tablet. These cracks may run through entire cracked pills or be localized. These defective tablets typically show no obvious signs of material breaking off and often require close observation or light pressure to be detected.
●Appearance Characteristics of Cracking
○Linear fissures are visible on the surface or in the cross-section, with a color consistent with the tablet body.
○Cracks may be distributed along the tablet diameter, edge, or center, and these defective tablets are prone to breaking under compression force.
●Key Causes of Tablet Cracking
○Granule Properties: Excessively low moisture content increases brittleness; insufficient binder quantity or low binding strength results in weak inter-particle bonds; uneven particle size distribution such as too many fines leads to uneven force distribution.
○Equipment Parameters: Excessively high tablet pressing speed makes particles lack time to bond fully; compression force fluctuations in pre-compression or main compression cause inconsistent pressure.
○Tooling Problems: Excessive clearance between a punch tip and a die bore causes uneven pressure when compressed tablets are ejected.
pill press machine tooling: lower punches, upper punches and dies
●Corrective Measures to Handle Tablet Deffects—Cracking
○Particle Performance Optimization: Incorporate efficient binders such as HPMC or PVP into formulation to enhance inter-particle bonding strength; control moisture content within 2%–5% to improve plasticity of tablet materials; optimize particle size distribution via fluid bed granulation or high-shear granulation to reduce the proportion of fine powder.
○Tablet Compression Adjustment: Appropriately reduce the tablet press speed (e.g., 15–25 RPM) to extend punches’ dwell time in dies and promote effective bonding of tablet ingredients; regularly calibrate pressure sensors and implement a gradient pressure profile between pre-compression and main compression to minimize fluctuations and ensure a stable tablet compression process.
○Tooling Maintenance: Periodically inspect the clearance between punches and dies; use cGMP-compliant tooling sets; replace severely worn molds in a timely manner; and perform no-load test runs before each tablet production batch to ensure mold alignment.
The capping defect refers to the partial or complete separation of a tablet’s top or bottom layer—surfaces in contact with upper or lower punches)—during tablet compression, resulting in cap-shaped fragments. Capping defect is one of the most serious tablet defects in tablet manufacturing, and commonly occurs in round pharmaceutical tablets especially those made of highly elastic granules.
●Appearance Characteristics of Capped Tablets
The detached portion is usually a thin layer, typically 1 or 2 mm thick, from the tablet surface, with a circular or irregular edge.
a pressure wheel (at the top) of a pill press
●Key Causes of Capping Defect
○Excessive Elastic Recovery of Granules: Certain crystalline active pharmaceutical ingredients or excipients undergo elastic rebound after tablet pressing, causing stress fractures when medication tablets separate from punches.
○Improper Pressure Settings: Excessive main compression pressure beyond granule tolerance, or insufficient pre-compression that causes stress concentration at tops of tablets during main compression.
○Punch and Die Issues: Irregular punch surface or misalignment between punches and dies results in uneven compression force distribution.
●Measures to Tackle Capping of Tablets
○Improve Granule Plasticity: Incorporate highly plastic excipients such as MCC or compressible starch. Use dry or wet granulation to enhance plasticity of tablet materials. If necessary, apply micronization or thermo-moisture treatment to strengthen inter-particulate bonds and reduce elastic recovery.
○Adjust Tablet Compression: Appropriately reduce main compression pressure without compromising tablet hardness requirements. Increase pre-compression pressure or extend pre-compression time to achieve staged compaction and minimize superficial stress concentration;
○Tablet Press Maintenance: Regularly inspect and polish punch surfaces. Maintain precise concentricity between punches and dies. Standardize tooling installation and debugging procedures to prevent capped tablets caused by mold wear or misalignment.
Compared to cracking and capping of tablets, chipping has a higher frequency to occur. When chipping occurs, small fragments break away from edges or corners of pharmaceutical tablets. Broken parts are small, usually appearing as notches on pill edges, do not affect main tablet surfaces, and only compromise the visual integrity.
●Appearance Characteristics of Chipping
The tablet edge shows missing corners or burrs; the damage often occurs at the ejection end of a die bore where compressed tablets rub against die edges during tablet ejection.
Without obvious cracks, these defective tablets only lose material at tablet edges.
●Key Causes
○Die Issues: Worn die bore edges or low smoothness of the die cavity inner wall can cause scraping during the ejection of drug tablets.
○Granule Properties: Poor flowability of tablet granules leads to uneven granule distribution at tablet edges and weak bonding after tablet pressing. In addition, high granule brittleness will cause tablet defects on edges.
○Ejection Parameters: Insufficient pill ejection pressure results in a situation that compressed tablets cannot be released smoothly from dies, increasing scraping.
●Solutions to Chipping
○Die Maintenance: Regularly inspect dies for wear; perform precision grinding to restore right-angle edges and high-gloss polishing of the die bore inner wall. Replace severely worn dies if necessary.
What’s more, a pill press tablet press machine with the integrated transferring function of punches and pressure wheels should be selected. By vertically moving upper and lower punches and pressure rolls as a whole, the tablet pressing position within die cavities can be altered, reducing friction at specific areas of die cavities and thereby prolonging the service life of tooling. Rich Packing’s RQ HGZP 26D intelligent rotary tablet press machine is a pill press sample equipped with this advanced feature, offering an output of up to 165,000 drug tablets per hour.
○Granule Optimization: Improve granule flowability by adding appropriate glidants such as silicon dioxide to ensure uniform filling. Adjust granulation process including modifying binder content to reduce granule brittleness and enhance tablet edge bonding strength.
○Ejection Adjustment: Gradually increase ejection pressure to ensure smooth and rapid tablet release. Monitor for abnormal friction or resistance during pill ejection.
Both issues are common tableting deffects where tablet materials adhere to the punch surface, but these two tableting deffects manifest differently:
●Sticking: Powder or granules evenly adhere to punch tip surfaces, resulting in rough, overly glossy, or powdery surfaces on pharmaceutical tablets.
●Picking: When a punch tip surface has engravings or logos, tablet materials become embedded in recessed areas and adhere, causing corresponding defects in tablets on tablet surfaces, such as incomplete branding words on the pill surface.
punches and round dies of a pharmaceutical pill tablet press
●Appearance Characteristics
In terms of sticking, the tablet surface shows no structural damage but has abnormal gloss, and residual material is visible on punch tips.
When it comes to picking, the tablet surface exhibits tablet defects matching punch engravings or recesses, with exposed tablet granules or blank areas in affected positions.
●Causes of Sticking and Picking
○Punch Condition: Rust, wear or the lack of anti-sticking coating such as Teflon causes insufficient smoothness of punch tip surface.
○Granule Properties: Excessive moisture content increases granule stickiness; high proportion of fine powder or insufficient lubricant such as low magnesium stearate content can lead to sticking issue.
○Environmental Factors: High ambient humidity lets tablet material absorb moisture; temperature rise during tablet compression causes tablet material softening. Both situations worsen sticking and picking.
a pill tablet press punch tip
●Solutions to Sticking and Picking
○Punch Maintenance: Regularly polish punch tips to maintain punch surface smoothness, repair damage, and apply anti-sticking coatings to ensure punches remain in good condition.
○Material Optimization: Strictly control granule moisture by applying drying treatment, reduce the proportion of fine powder through sieving, and appropriately add lubricants such as 0.5%–1% magnesium stearate to enhance anti-sticking properties.
○Environmental Control: Maintain workshop humidity at 40%–60%, and install temperature control equipment to cool punches if necessary, preventing excessive temperatures of tablet manufacturing process.
In flaking scenario, a thin layer of the tablet surface peels off in flakes. The peeled material is relatively thin similar to skin, and the affected area is larger than that of cracking but smaller than that of capping.
●Causes of Flaking
○Uneven Granule Binding Force: Significant difference in binding force between surface and internal granules gives rise to this tablet defect. For example, excessive fine powder on tablet surface leads to weak bonding after tablet compression.
○Excipient Issues: Uneven distribution of binder in granules or excessive use of low-adhesion excipients such as lactose will result in this type of defective tablets.
○Pressure Parameters: Insufficient pre-compression fails to achieve fully compacted surface granules, leading to separation from a tablet’s internal structure.
As for corrective measures to address issues above, we are going to recommend you more concrete steps in future articles about tableting deffects.
When manufacturing tablets, avoiding above tablet defects such as capping, cracking, and flaking is essential to ensure quality of pharmaceutical tablets. A key step is investing in a reliable rotary tablet press equipped with critical features designed to eliminate defects in tablets. A reliable pill machine tablet press should include
●Pre-compression: This system removes air within tablet granules and powder, improves tablet material plasticity, and ensures thorough compression.
●Specially Coated Punches: Teflon-coated punches address sticking issue. Moreover, chromium-coated punches help prevent sticking and picking, and resist high heat, corrosion, and wear.
●Precision Finishing of Dies: Dies must go through mold roughness measurement and secondary processing to ensure tooling durability and consistent tablet formation.
●Real-time Monitoring & Waste Rejection: This system automatically detects and removes under or over-weight tablets in single-piece method, ensuring tablet uniformity without defective tablets.
an automatic pill tablet press machine
By integrating these features, tablet manufacturers can reduce tablet defects and maintain high tablet production standards.
Effectively tackling tablet defects in tablet manufacturing requests a thorough comprehension of causes and carrying out practical corrective measures. By putting importance to pill presses with advanced functionalities, tablet manufacturers can keep away defects in tablets and enhance the integrity of medication tablets.
E-mail : manager@richpacking.cn
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