Tablet compression machine (also referred as tablet press machine, tablet machine, or tablet punching machine) is a mechanical device that is used to compress the granules or mixture of API and excipients to uniform and predetermined size, shape and weight of tablets for research, pilot scale and full production.
Types of tablet compression machine
Based on punch number, tablet press machine can be classified into;
1. Single punch tablet compression machine/ single station/ Eccentric tablet press machine
Single punch tablet press machine that uses a pair of punches (upper and lower) and a die to compress granules/ powder mixture to make tablets for research and small scale production.
2. Multi punches tablet compression/ multi-station/rotary presses
Multi-station press is a mechanical device that unlike single punch tablet press has several stations which rotate to compress granules/powder mixture to uniform size, shape and weight of tablets with high productivity in short time.It was developed to raise the productivity of tablets.
Core functional parts of the rotary tablet press machine are
Hopper
The hopper holds and supplies the granules/ powder mixture (active ingredients and excipients) to the feeder system. It is the input point of powder mixture or granules to tablet press for compression of tablets. Granules or powder mix may feed manually or using automated system.
Feeder system
Feeder system helps to force the feed of the granules into the die cavity, especially during faster rotation. It also mixes the granules to inhibit the separation of granules. Feeder system is also called a force feeder. The force feeder of tablet compression machine contains two vital parts
i. Feed peddles
It rotates continuously and ensures consistent and accurate granules feed into the die cavity in a high speed machine.
ii.Feeder housing
Through the feeder housing, granules for tablets from the hopper will enter into the die system.
Feed frame
Some tablet press machine have a feed frame rather than feed system(feed paddle and feeder housing). The feed frame delivers the granules or powder mix into the die cavity under the influence of gravity. Tablet scraper and excess granules stripper must attach to the feeder system or feed frame.
Excess granules stripper
This part of the tablet press machine takes away extra granules from the surface of the die bore or cavity. The granules stripper is liable for controlling the volume of granules and ultimately the weight of the tablets.
Die
Die defines the size and the shape of the tablet. Powder mix or granules are compressed into the desired size, diameter, and shape of tablets in die bore or die cavity.
Punch
Two punches (upper and lower) compress the granules/powder mix in the die bore. The lower punch moves upward and the upper punch moves downward and compresses the tablet within the die cavity. Then the upper punch moves upward and the lower punch moves downward.
Turret
Turret hosts the die as well as upper and lower punches on its holes and ensures the position of the die bore and two punches (lower and upper) for the tablet compression process. The turret is the heart-like part of the tablet press machine.
Cam track
Cam track guides the movement of both the upper and lower punches in the tablet compression process that plays an integral role in ensuring a smooth tableting process. As a turret rotates, the cam track helps to move the punches in up and down motion.
Compression rollers
Tablet press machines have rollers that exert a predetermined and sufficient amount of force to compress the granules into tablets with desired hardness. Most tablet press machines have two sets of compression rollers.
Pre- compression roller
They give initial compression force. The aim of pre- compression is to eliminate air that could be in the die or granules/powder mix.
Main compression roller
It exerts sufficient compression force to compress the granules into tablets. The rollers stay stable with no vibration during the entire compression process to ensure consistent thickness and size of the tablet.
Ejection cam
Ejection cam guides the lower punch upwards assisting the ejection of tablets from the die bore or cavity after compression. The ejection cams slowly and gradually push the lower punch upwards.
Take-off blade/ tablet scraper
This is fitted in front of the feed frame or feeder system and scrap the compressed tablet to the discharge chute. The tablet scraper (also known as takeoff scraper or tablet take-off) pushes the compressed tablets away from the die table of the compressing machine to the discharge chute.
Discharge chute
Guides the compressed tablets to a collection drum or bin.
Tablet weight controller
This is used to adjust the volume of the granules to be compressed and so determines the weights of the tablet with the help of different movements of the cam systems, material will flow into the die cavity depending on the position of the punches.
Other tablet compression machine parts
- Safety system
-touch screen display and control panel
-belts,gears, electric motors
-Lubrication system
-Hydraulic pump system
Ingredients used in tablet formulation
In addition to the active drug, called active pharmaceutical ingredient (API), tablets may contain one or more of functional ingredients such as diluents (also known as fillers), binders, disintegrants, glidants, lubricants, coating materials, coloring agents, stabilizer(s), sweeteners, and flavoring agents. These ingredients are called excipients.
Excipients
These are inert substances used as diluents or vehicles for a drug. In the pharmaceutical industry it is a catch-all term which includes various sub-groups comprising diluents or fillers, binders or adhesives, disintegrants, lubricants, glidant, flavors, colors and sweeteners.Excipients are added to improve one or more of the three key functional properties of a dosage form:
(1) bioavailability,
(2) manufacturability, and
(3) stability.
All of these must meet certain criteria as follows
a) Physiologically inert.
b) Acceptable to regulatory agencies.
c) Physiologically and chemically stable.
d) Free from bacteria.
e) Should not interfere with the bioavailability of the drug.
f) Commercially available in the form and purity commensurate to pharmaceutical standards.
g) Low cost, inexpensive.
h) Meet the standards of regulatory requirements
Diluents:
Diluents are fillers used to make up the volume of tablet if tablet is inadequate to produce the volume. Diluents used as disintegrants in dispersible and orally disintegrating tablet.
Example: anhydrous lactose, lactose monohydrate, sorbitol, Micro crystalline cellulose, dibasic calcium phosphate dehydrate, Calcium sulphate dehydrate.
Binders:
Binders are used as binding agent in tablets; it provides cohesive strength to powdered materials. Binders are added in both dry and wet form to form granules.
Example: Gelatin, glucose, Lactose, cellulose derivatives-methyl cellulose, Ethyl cellulose, Hydroxy propylmethyl cellulose,Hydroxy propyl cellulose, starch, Poly vinyl pyrrolidone , Sodium alginate, Carboxymethylcellulose, Acacia.
Lubricants:
Used to reduce the friction between die wall and tablet, prevent adhesion of tablet to dies and punches. Helps in easy ejection of tablets from die cavity. Classified in to 2 types.
i. Insoluble- Example Stearic acid, Magnesium stearate, Calcium stearate, Talc, Paraffin.
ii. Soluble-Example Sodium lauryl sulphate, Sodium benzoate, PEG 400, 600,8000
Glidants:
Helps in free flowing of granules from hopper to die cavity. Minimize friction between particles.
Example: Colloidal Silicon dioxide (Aerosil), Cornstarch, Talc.
Anti-adherents:
These are added to prevent adhesion of tablet material to punches and dies. Prevent sticking of tablet to dies and punches.
Example: Talc
Disintegrants:
When they come in contact with water in oral cavity/GIT break down in to small particles.
Example:Alginic acid ,Crospovidone , Microcrystalline cellulose, Pregelatinized starch ,Sodium croscarmellose, Sodium starch glycolate , Starch
Role of disintegrants in the manufacturing of tablets
Disintegrating agents are substances included in tablet formulations and in some hard shell capsule formulations to promote moisture penetration and dispersion of the matrix of the dosage form in dissolution fluids.
An oral solid dosage form should ideally disperse into the primary particles from which it was prepared. Although various compounds have been proposed and evaluated as disintegrants, relatively few are in common usage today. Traditionally, starch has been the disintegrant of choice in tablet formulations, and it is still widely used.
For instance, starch generally has to be present at levels greater than 5% to adversely affect compactibility, especially in direct compression. Moreover, intra granular starch in wet granulations is not as effective as dry starch.
Characteristics of disintegrant
The ideal disintegrant should have the following characteristics:
Ø Poor solubility
Ø Poor gel formation
Ø Good hydration capacity
Ø Good compressibility and flow properties
Ø No tendency to form complexes with the drugs
Factors affecting action of disintegrants
• Percentage of disintegrants present in the tablets.
• Types of substances present in the tablets.
• Combination of disintegrants.
• Presence of surfactants.
• Hardness of the tablets.
• Nature of Drug substances.
• Mixing and Screening.
Flavouring agent:
Used in chewable or dispersible tablets or in coating suspension for bad smell tablets Example; vanillin, cinnamon, grape.
Surfactant:
Surfactants, or surface-active agents, are amphiphilic molecules that contain both a polar and non-polar region that can function as emulsifying, wetting, and solubilizing agents . The amphiphilic nature of surfactants is responsible for two important properties of these compounds that account for a variety of interfacial phenomena. One is the ability of surfactant molecules to adsorb at gas–liquid, liquid–liquid, and solid–liquid interfaces to reduce interfacial tension.
They also have a tendency to self-associate and form aggregates or micelles once the critical micelle concentration is exceeded. The ability of surfactants to reduce interfacial tension is critical to emulsification and wetting while micelle formation enables the solubilization of water-insoluble compounds.
These excipients are added to formulations to facilitate the wetting or solubilization of the drug substance.
Examples:Sodium lauryl sulfate, Docusate sodium, Lecithin, Poloxamer, Polysorbate 80
Colouring agents: Gives a colour to a tablet Example Tartazine, quinoline, sunset yellow.
Coating materials
Pharmaceuticals may be coated for several reasons including taste masking, improving ingestion, improving appearance, ease of identification, protecting active ingredients from the environment, and controlling drug release in the GI tract
Example:Hypromellose, Ethylcellulose, Methylcellulose, Ammonio methacrylate copolymer, Cellulose acetate, Cellulose acetate phthalate, Methacrylic acid copolymer, Sucrose.
Drug Release Modifying Agents
A variety of excipients, typically polymeric, may be used to delay the release of drug from a dosage form. Common technologies used for this purpose include: matrix tablets, multiparticulate– coated particles, and osmotically controlled dosage forms. Selection of the release-modifying agent is dependent upon the drug properties and the drug release profile that is needed to optimize dosage form performance.
In comparing the tables of excipients provided here, it is clear that excipients may serve different functions depending on how they are used in a formulation. For example, P.582
hypromellose (HPMC) may be used as a tablet binder, a delayed release agent, or a tablet-coating agent depending on the quantity and processing methods used.
Ø https://www.rroij.com/open-access/excipients-used-in-the-formulation-of-tablets-.php
Ø martins-physical-pharmacy-6th-ed-2011-dr-murtadha-alshareifi
Ø Remington_The_Science_and_Practice_of_Pharmacy_20th_Edition_
Ø https://www.lfatabletpresses.com/articles/types-tablet-press
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