CONSTRUCTION AND WORKING OF TABLET PRESS2

CONSTRUCTION AND WORKING OF TABLET PRESS:

CONSTRUCTION AND WORKING OF TABLET PRESS By venkatesh.k m.Pharm 1 st sem (I.P) Vaagewari college of pharmacy

Contents:

Contents Introduction Machine instrumentation Working of tablet press Process of compression Conclusion Referencess

INTRODUCTION:

INTRODUCTION OBJECTIVE: The intention of this chapter is not to make the pharmacist a tool designer, but to give sufficient background on the subject so that possible production problems can be minimized. TERMINOLOGY To best understand the tablet instrumentation ,it is necessary to be familiar with following the commonly accepted terminology. Punch land : Area between the edges of the of the punch cup and outside diameter of the punch tip. Head: End of the punch that is controlled by the machine camming . Head flat: Area receiving the force of the compression rolls at the tablet is being formed.

Slide 4:

Rockwell: hardness of the tool. Overall length: total length of the punch. Working length: from bottom of the cup to head flat. Galling: Roughly worn areas . Chamfer: Entry n the die bore. Ring: Eroded area on the die bore. Tablet flush: semi compressed material formed on the perimeter of the tablet. AISI: American Institute of Steel Industries. Key angle: Device on the upper punch to keep it aligned when the punch tip is out of the die bore to permit proper re-entry.

Slide 5:

Die groove: Accept the press locking screw. Taper: Gradual increase in the die bore diameter from the point of compaction to the die chamfer area. Capping: Laminar separation. Picking: Granulation adherence to the punch face. Strain gauges: these are transducers for measuring the magnitude of the force operating during compression cycle Double impression: double imprint of logo due punch rotation from pre compression roller to compression roller.

MACHINE INSTRUMENTATION:

MACHINE INSTRUMENTATION The tablet press comprises of following parts. Punches Dies Auxiliary equipments

PUNCHES:

PUNCHES These are two types. Upper punch and lower punch. Neck of the upper punch is smaller than the lower punch These are made by steel , in order to withstand with the force existed by rollers. Both upper & lower punches are same in length except in “B” tooling. For large dose preparation D tooling is preferable.

Parts of punch:

Parts of punch

Punch cup contour(design):

Punch cup contour(design)

Slide 10:

Selection of punch depends on two factors. 1. force applied 2.shape required For heavy forces shallow or standard cups are preferable.

Maximum recommended compression force verses punch tip diameter for standard steel punches:

Maximum recommended compression force verses punch tip diameter for standard steel punches Diameter Flat faced/shallow/std concave Deep/extra deep/ flat faced bevel edge 3/32 3.1 1.2 5/32 8.5 3.4 7/32 16.5 6.7 9/32 27.5 11.1 13/32 57.5 23.5 15/32 77.0 30.0 17/32 98.5 39.5 9/16 110.0 44.0 11/16 165.0 66.0 13/16 230.5 92.0 1 349.0 139.5

Steel Hardness and Selection::

Steel Hardness and Selection: Several types of tool steel are normally used in the fabrication of compression tooling. The proper selection becomes critical to a successful overall operation. The steel characteristics to be looked for in descending order of importance. 1. Toughness to withstand the cyclic compaction forces 2. Wear resistance 3. Cost

Comparison :

Comparison standard Type S 5 : shock resistance silicone steel. good ductility and toughness. If 3 3% Nickel is added to S 5 which has greater ductility but less resistant to abrasion than the S 5 . premium Types: D2 & D3 High carbon & chrome alloys. Greater resistance. But less ductility which result in breakage. Used for light compaction forces.

AISI DESIGN:

AISI DESIGN 3% Nickel S 5 S7 A2 01 D2 440C D3 9 T 8 O 7 U 6 G 5 N 4 E 3 S 2 S 1 0 1 2 3 4 5 6 7 8 9 W E A R R E S I S T A N C E Tool steel-wear /toughness chart

COMPOSITION OF ALLAYS:

COMPOSITION OF ALLAYS Many types of allays are available but following cobalt composition are preferred. Cobalt 36 to 68% of weight. Chromium 26 to 36% of weight. Tungsten not more than 17%. Carbon 0.25 to 3% of weight. Iron not more than 3% of weight. Silicon not more than 2% of weight. Nickel 22% of weight .

Stainless steels:

Stainless steels Austentic Series 300. Nickel contains. Used for tanks, sinks, sterile equipment...etc. Not accept heat treatment. Martensitic Series 400. Little or no nickle. Heat treatment can done. Poor corrosion resistance. hardness RC 58

Steel selection based on:

Steel selection based on Shape of the punch cup. Compressing force. Material nature. Ex : abrasive, corrosive(stainless steel)

Slide 18:

These allays can withstand higher temperature and pressure, temp 400 C. Punches and dies properly handled, if tip of a punch damages which results in change in tablet shape. Punches and dies should be keep in a given boxes after work completes. Otherwise will get rust. Shape of a tablet depends upon the shape of tip. Tip of a punch can be designed, as for manufacturer interest.

DIES:

DIES These are holded by die table. These are in different sizes , made by steel. Selection of die depends upon the dose we wanted. Diameter of a tablet depends upon the die we select. These are available in different diameter. Die is fixed by the die screw. For large size tablets D tooling dies are preferable.

TOOLING ( in inches):

TOOLING ( in inches) Tooling type& punch parameters BB B D Barrel length 5.25 5.25/3.56 5.25 Barrel diameter 0.75 “” 1 Head diameter 1 “” 1.25

Slide 21:

Arrangement of punches and dies

Auxiliary parts:

Auxiliary parts These includes Tablet dedusters. Hopper. Chute. Compression analyzers. Signal conditioning systems. Strain gages.

Production rate depends on :

Production rate depends on Number of stations. Number of compressions per cycle. Speed of the turrets.

Selected rotary tablet press characteristics.:

Selected rotary tablet press characteristics . Manufacturer Number of stations available Min Max Tablet per minute(TPM) Min Max Colton 12 90 480 1600 Whilhelm Fette,Gmbh , HumburgW . Koln 20 55 300/900 3300/8250 Killian & Co ., Gmbh Koln, W.Germany 14 67 140/383 1083/10,000 Mnesty machine ltd.Liverpool,England . 16 69 600/1500 3330/10,000 Stroke merril 33 65 1200/3300 3500/10,000 Hatta Iron works,Horry Engineering Co. Osaka, Japan 28 71 420/1420 1920/7100

Differences between single & rotary tablet presses:

Differences between single & rotary tablet presses Single punch machine Consist of one station. production rate low. Tpm is aproximatly 100. Lower punch do nt move wile compression. Ex: Rotary machine More stations. Production rate is high. Tpm is 10,000. Both punches move. ex: colton

Working of tablet press:

Working of tablet press Irrespective of the tablet press types ( single station or rotary) the following steps are majorly involved. Filling. Weight adjusting. Compression. Ejection.

Illustration of tablet compression :

Illustration of tablet compression

The process of compression:

The process of compression Among all the steps, compression is the most important step. For better understanding it is further devided as follows. Transitional packing or particle rearrangement. Deformation at point of contact. Fragmentation & Deformation. Bonding Deformation of the solid body. Decompression

Measurement of compressional force:

Measurement of compressional force Tablet presses designed on the principle that the force on a punch is proportional to the force transmitted to other parts of the tablet machine. The instrumentation of a tablet press has been by means of bonding strain gages to upper & lower punches and transmitting the strain from the strain gages with a radio link or means of bonding strain gages to a stationary locations near to the site of compression.

A typical force time curve for the upper & lower punches is shown:

A typical force time curve for the upper & lower punches is shown

From the chart we can predict the following :

From the chart we can predict the following AB shows repacking, deformation at the point of contact, fragmentation, and bonding occurs. At B consolodidation of the tablet occurs. At BC decompression occurs while ascending of upper punch. The deep line below the base line is a measure of the force required to remove the upper punch from the die. The recorder line drops below the base line ,measuring the force of ejection .

Slide 33:

The segment EF of lower punch curve shows that upper punch force is transmitted to the stationary lower punch. The FG is measure of the force exerted by the tablet on die wall. This is the minimum force required to eject the tablet.

ENERGY EXPENDITURE:

ENERGY EXPENDITURE AS the upper punch enters the die and begin to apply a force to the granulation, a small quantity of energy is used to re-arrange the particles to pack with less void. As the process of compression continues, energy is expended to overcome die wall friction and to increase the specific surface as fragmentation and/ or deformation occurs. After the tablet has been consolidated energy is required to overcome die wall friction as the upper punch is withdrawn. Energy is then expended in the ejection of the tablet form the die .

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The energy expenditure is the sum of the energy dissipated as heat, the energy of reversible plastic strain and the energy retained in the tablet as increased surface energy. The useful energy of compression is E compression = E total -( E heat + E elastic ) By using of an internal temperature probe found a 2 to 5C rise in the temp. of tablets compressed from MCC , calcium carbonate and sulfathiazole.

Energy expended in compression of 400 mg of sulfathiazole granulation in a single punch tablet machine given in table. Force1200 kg on lower punch using 3/8 in (9.525mm) flat faced punch:

Energy expended in compression of 400 mg of sulfathiazole granulation in a single punch tablet machine given in table. Force1200 kg on lower punch using 3/8 in (9.525mm) flat faced punch compression lubricated Un lubricated compression 1.5 1.5 Over coming die wall friction - 0.8 Upper withdrawal - 1.2 Tablet ejection 0.5 5.1 Total 2.0 8.6

Effect of various lubricants for compression of a sulfathiazole granulation:

Effect of various lubricants for compression of a sulfathiazole granulation lubricant percent Max.lower punch force/max. upper punch force control - 0.63 Calcium stearate 0.5/1.0/2.0 0.96/0.98/0.99 Sodium stearate 0.5/1.0/2.0 0.86/0.94/0.95 spermaceti 0.5/1.0/2.0 056/0.66/0.68 Peg 4000 0.5/1.0/2.0 076/0.79/0.74 talc 0.5/1.0/2.0 0.60/0.60/0.63 Mg. stearat 0.5/1.0/2.0 0.83/0.86/0.88

Disintegration time against % of lubricant for sod.by carbonate tablets compressed at 1300kg/cm:

Disintegration time against % of lubricant for sod.by carbonate tablets compressed at 1300kg/cm

Conclusion:

Conclusion Instrumental tablet machine technology is advancing rapidly. It enables better understanding of the tablet press which in turn in assist in formulation development and batch quality control. A well thought out design that satisfies the needs of production, packaging and marketing, coupled with the manufacturer of the tools to exacting specifications required, are necessary to produce the height quality product at the lowest overall cost.

References :

References Text book of modern pharmaceutics. 4 the edition by Banker.(p 362-318). 2.Pharmaceutical dosage forms: tablets, vol 2, sec.editoin by A. Lachman , leon Lachman & Joseph B. Schwatz .(201-241 & 571- 608). 3.The theory and practice of industrial pharmacy, 3 rd edition by leon Lachman ,A. Libberman , Joseph L. Kanig .(p. 301-311) Pharmaceutics, the science of dosage form design, 2 nd edition by M.E. Aulton

Thank you:

Thank you