HOT POST

50/recent/ticker-posts

Header Ads Widget

Compression - Problems and Remedies

Tablet Weight 

Weight variation outside Limits

Causes : Remedies
  • Poor or erratic powder flow, flooding: Correct powder flow problem
  • Particle size range too wide:
  1. Narrow the particle size range; avoid excess fines
  2. 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: 
  1. Narrow the particle size range. 
  2. Compress at slower RPM
  • Lower punch “hang up” (material between lower punch and die wall or lower punch and punch guide):
  1. Clean; improve dust collection
  2. Check for proper clearance between die wall and lower punch
  3. Increase lubricant concentration in formulation.
  4. 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:
  1. Increase or change lubricant; use microfine lubricants; screen into mix.
  2. 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:
  1. The process under low humidity conditions
  2. Use moisture scavengers (e.g., calcium silicate, Syloid, Cab-O-Sil)
  • Adhesive components
  1. Increase lubricant level
  2. Add 0.5% Cab-O-Sil or Syloid
  3. 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:
  1. Avoid using certain letters. (e.g., “A”, “B”, “P”, “R”)
  2. 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 :
  1. Increase or change the lubricant
  2. Use microfine lubricants, screen into the mix.
  3. Increase lubricant mixing time
  • Insufficiently dried wet: Dry granulation and establish granulation moisture limits
  • Hygroscopic components: 
  1. Process under low humidity conditions. 
  2. Use moisture adsorbent (e.g., calcium silicate, Syloid)
  • Adhesive components:
  1. Increase lubricant level. 
  2. 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
  1. Exclude or reduce to a fine particle size
  2. Increase lubricant level
  3. Blend abrasive component directly with the lubricant
  4. Use minimum tableting pressure possible
  5. 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:
  1. Use a stronger binder or additional binder
  2. 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:
  1. Decrease lubricant level
  2. 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): 
  1. Use precompression on a tablet press. 
  2. 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

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: 
  1. Redesign using tapered sides on the punch debossing. 
  2. 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
  • Overlubrication:
  1. Decrease lubricant level
  2. 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)
  • Overlubrication:
  1. Decrease lubricant level
  2. Blend lubricant for minimal time required; establish optimum mixing time
  3. Replace metallic stearates with other lubricants (e.g., stearic acid)
  • Granulation too soft:
  1. Use additional binder
  2. 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 underdried or high humidity in compressing area): 
  1. Determine optimum moisture content. 
  2. Use moisture adsorbent (e.g., calcium silicate, Syloid)
  • Moisture content too low (granulation overdried or low humidity in compressing area): 
  1. Determine optimum moisture content. 
  2. Add additional moisture

Variable Hardness

Causes : Remedies
  • Tooling: Examine punch lengths
  • Uneven diefill: See “Table Weight: Weight variation
  • Overblending: Optimize blending time to minimize creation of fines

High Friability

Causes : Remedies
  • Inadequate bonding of the tablet mix:
  1. Increase binder level or change to stronger binder
  2. Add or increase Avicel PH-101 or PH-102 (10% to 20%)
  3. Avicel PH gives low friability at lower hardness/machine pressures
  • Too much or too little compression pressure: Adjust pressure for acceptable friability
  • Overlubrication:
  1. Decrease lubricant level
  2. Blend lubricant for minimal time required; establish optimum mixing time
  3. Replace metallic stearates with other lubricants (e.g., stearic acid)

Disintegration too Long

Causes : Remedies
  • Tablet hardness too high: 
  1. Reduce machine pressure for acceptable tablets. 
  2. Use less binder in granulation.
  • Overlubrication (Waterproofing):
  1. Decrease lubricant level
  2. Blend lubricant for minimal time required; establish optimum mixing time
  3. Replace metallic stearates with other lubricants (e.g., stearic acid)
  • Requires additional disintegrant or a different disintegrant
  1. Consider a “super disintegrant” (e.g., Ac-Di-Sol, 2% to 5%)
  2. Include Avicel PH-101 or PH-102 (added dry), about 10% as an auxiliary disintegrant
  3. 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: 
  • Preferential absorption of soluble dye by component of mix: 
  1. Replace causative component. 
  2. Replace soluble dye with microfine lake pigment
  • High level of uncolored additives (e.g., fillers, lubricants, disintegrants): 
  1. Reduce quantity of additives. 
  2. Color additives with soluble dye or mix with lake pigment.
  • In direct compression, uneven distribution of lake dye :
  1. Use microfine lake dye.
  2. Increase blending time
  3. Mill lake dye with 5% excipient, then blend with bulk
  4. Reduce size of larger particles of excipient or active
  5. 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.

Post a Comment

0 Comments

close