Tablet Weight
Weight variation outside Limits
Causes : Remedies
- Poor or erratic powder flow, flooding: Correct powder flow problem
- Particle size range too wide:
- Narrow the particle size range; avoid excess fines
- Use Avicel PH-200 to minimize weight variation
- Particle size not suitable for die diameter: Adjust particle size range to recommended optimum for die diameter
- Punches not within specifications: Examine punch length dimensions
- Particle segregation as press RPM’s increase:
- Narrow the particle size range.
- Compress at slower RPM
- Lower punch “hang up” (material between lower punch and die wall or lower punch and punch guide):
- Clean; improve dust collection
- Check for proper clearance between die wall and lower punch
- Increase lubricant concentration in formulation.
- Remove below 200 mesh fines
Punches and Dies
Punch binding (powder adheres to punch edges and dies punches may bind in dies)
Causes: Remedies
- Poor finish or worn punches and dies: Polish, reface, or replace tooling
- Inadequate lubrication:
- Increase or change lubricant; use microfine lubricants; screen into mix.
- Increase lubricant blending time
- Too many fines or coarse particles in mix: Design better particle size range; use tapered dies
- Wet granulation insufficiently dried: Dry granulation to satisfactory moisture limits
- Hygroscopic ingredients:
- The process under low humidity conditions
- Use moisture scavengers (e.g., calcium silicate, Syloid, Cab-O-Sil)
- Adhesive components
- Increase lubricant level
- Add 0.5% Cab-O-Sil or Syloid
- Add 5% to 10% low moisture grades Avicel PH-112 and PH-113
Punch filming or sticking (picking)— (powder adhesion to punch faces, usually upper)
Causes : Remedies
- Poor finish on punch faces: Polish punch faces; refinish
- Embossed letters:
- Avoid using certain letters. (e.g., “A”, “B”, “P”, “R”)
- Use shallow embossing with tapered edges rather than edges directly perpendicular to the punch face
- Punch tips burred: Refinish or replace
- Punch concavity too great: Reduce punch concavity or use flat face punches
- Poor binding between surface granules or particles: Increase binder (wet or dry)
- Low melting point ingredient: Adsorb low melting point ingredient on Avicel, replace with higher melting point ingredient
- Inadequate lubrication :
- Increase or change the lubricant
- Use microfine lubricants, screen into the mix.
- Increase lubricant mixing time
- Insufficiently dried wet: Dry granulation and establish granulation moisture limits
- Hygroscopic components:
- Process under low humidity conditions.
- Use moisture adsorbent (e.g., calcium silicate, Syloid)
- Adhesive components:
- Increase lubricant level.
- Add 0.5% Cab-O-Sil or Syloid or 5% to 10% Avicel PH-101.
- Tablets too soft: Increase compression pressure
Punch and Die Abrasion
Causes : Remedies
- Abrasive components
- Exclude or reduce to a fine particle size
- Increase lubricant level
- Blend abrasive component directly with the lubricant
- Use minimum tableting pressure possible
- Use more wear-resistant tooling (harder metal)
Capping and Laminating
Capping: is the separation of the top or bottom from the main body of the tablet.
Laminating: is transverse cracking and separation of the tablet into two or more layers.
Causes : Remedies
- Inadequate bonding of the powder particles (direct compression) or granules (wet granulation) to form cohesive tablets:
- Use a stronger binder or additional binder
- Avicel PH-101 and PH-102 are particularly effective direct compression binders (15% to 25%) and as auxiliary binders in wet granulation (5% to 15%).
- Poor finish or worn punches and dies: Polish, reface, or replace. Chrome plate punch faces
- Too many fines in granulation: Modify granulation process for minimum fines
- Granulation too dry: Adjust moisture level and establish optimum moisture limits
- Granulation too wet (usually associated with sticking or picking): Continue to dry and establish optimum moisture limit
- Over lubrication of the final tableting mix:
- Decrease lubricant level
- Blend lubricant for the minimal time required; establish optimum mixing time
- High level of ingredient with poor compression properties (also sometimes ascribed to air-entrapment by powder bed):
- Use precompression on a tablet press.
- Slow the speed of the tablet machine
- Punch concavity too deep: Change to standard concave or flat face punches
- Punch edges are worn or damaged: Refinish or replace
- Lower punch too low at tablet take-off: Adjust lower punch flush with die face
- Compression too low in die cavity: Compress in the upper portion of the die
- Excessive tableting pressure: Decrease pressure
- Die wall binding: Use sufficient lubricant. Use tapered dies
ALSO READ: What is Tablet Binding? Causes and Remedies
Chipping/Splitting
Causes : Remedies
- Poor finish or worn punches and dies: Polish, reface, or replace punches and dies
- Lower punch setting too low at tablet takeoff: Adjust lower punch flush with die face
- Tablet sweep-off blade on feed frameset too high: Adjust setting
Scoreline or Tablet Imprint Not Sharp
Causes : Remedies
- Faulty punch debossing design:
- Redesign using tapered sides on the punch debossing.
- Chrome-plate punch face
- Granulation too coarse: Reduce particle size of granulation
- Binder not strong enough: Use a stronger binder
Layered Tablets Splitting
Causes : Remedies
- Poor bonding between layers: Use a stronger binder or higher concentration
- Compression pressure too high: Compress at lower pressures
- Over lubrication:
- Decrease lubricant level
- Blend lubricant for minimal time required; do not blend for long periods of time
Layers not Sharply Defined
Causes : Remedies
- Granulation too coarse: Reduce particle size of granulation - less than 16 mesh
- Too many fines: Remove fines below 200 mesh
Low Hardness
Causes : Remedies
- Compression force (pressure) too low: Increase pressure (caution: do not exceed recommended pressure for punch size used)
- Over lubrication:
- Decrease lubricant level
- Blend lubricant for minimal time required; establish optimum mixing time
- Replace metallic stearates with other lubricants (e.g., stearic acid)
- Granulation too soft:
- Use additional binder
- Direct compression - use additional Avicel® PH
- Excipient (i.e., too much starch can give a soft tablet): Reduce level of causative excipient
- Moisture consent too high (granulation under dried or high humidity in compressing area):
- Determine optimum moisture content.
- Use moisture adsorbent (e.g., calcium silicate, Syloid)
- Moisture content too low (granulation overdried or low humidity in compressing area):
- Determine optimum moisture content.
- Add additional moisture
Variable Hardness
Causes : Remedies
- Tooling: Examine punch lengths
- Uneven die fill: See “Tablet Weight: Weight variation”
- Over blending: Optimize blending time to minimize creation of fines
High Friability
Causes : Remedies
- Inadequate bonding of the tablet mix:
- Increase binder level or change to stronger binder
- Add or increase Avicel PH-101 or PH-102 (10% to 20%)
- Avicel PH gives low friability at lower hardness/machine pressures
- Too much or too little compression pressure: Adjust pressure for acceptable friability
- Over lubrication:
- Decrease lubricant level
- Blend lubricant for minimal time required; establish optimum mixing time
- Replace metallic stearates with other lubricants (e.g., stearic acid)
Disintegration too Long
Causes : Remedies
- Tablet hardness too high:
- Reduce machine pressure for acceptable tablets.
- Use less binder in granulation.
- Over lubrication (Waterproofing):
- Decrease lubricant level
- Blend lubricant for minimal time required; establish optimum mixing time
- Replace metallic stearates with other lubricants (e.g., stearic acid)
- Requires additional disintegrant or a different disintegrant
- Consider a “super disintegrant” (e.g., Ac-Di-Sol, 2% to 5%)
- Include Avicel PH-101 or PH-102 (added dry), about 10% as an auxiliary disintegrant
- Consider adding a surfactant (e.g., DOSS, 0.1%)
- Tablet hardness too low: Increase hardness to allow swellable disintegrant to function
Mottling
Causes : Remedies
- Uneven distribution of the dye in colored tablets: Increase mixing time or use high shear mixer
- Dye migration during drying process:
- See “Drying: Color migration”.
- See “Dry screening: Poor color distribution”
- Preferential absorption of soluble dye by component of mix:
- Replace causative component.
- Replace soluble dye with microfine lake pigment
- High level of uncolored additives (e.g., fillers, lubricants, disintegrants):
- Reduce quantity of additives.
- Color additives with soluble dye or mix with lake pigment.
- In direct compression, uneven distribution of lake dye :
- Use microfine lake dye.
- Increase blending time
- Mill lake dye with 5% excipient, then blend with bulk
- Reduce size of larger particles of excipient or active
- Use lower drying temperature.
Tablets contain “dirty” specks
Causes : Remedies
- Misaligned upper cam tracks - rubbing of punches on cam actually rubs off metal which is introduced into material being compressed: Check alignment of upper cam tracks
- No lubrication on upper cam tracks: Check alignment of upper cam tracks
- Excessive or improper lubrication on upper punch shanks (no dust caps on punches) - dust mixes with excess oil or grease and falls into material being compressed: Use dust caps on upper punches
Tablets Uniformly Discolored
Causes : Remedies
- Feed frame rubbing on die table: Check clearance between feed frame and die table
- Feed hopper rubbing on turret: Check clearance between feed hopper and turret
- Abrasive materials wearing screens, scooper, etc.: Check for presence of abrasive materials.
Tags
Production
