About pressing of tablets

Overview designs popular models of rotary presses
Rotary or rotary tableting machine
The main difference between a rotary tablet machine (RTM) from eccentric - the large number of punches and mounted in a rotating matrix table matrices. In rotary tablet press machine is gradually increasing and uniform and soft pressing powder. Rotary presses have high productivity - up to half a million tablets per hour.
Cycle on rotary tableting presses technologically includes a series of successive operations:
Volumetric dosing method: matrix filled tabletiruemoj mass.
Pressing directly.
Finished tablets are ejected from the dies.
Tablets are dropped from the die table.
The sequence of these operations is performed in the automatic mode. The pressing rollers exert simultaneous pressure on the upper and lower punches, sliding along the guide (Kapiri). Uniform and soft pressing tablets from above and below is achieved gradually increasing and decreasing pressure. Rotary tabletting machine, depending on the type, may be fitted with one or two fixedly mounted hoppers, which can set the mixer.
Movement of each matrix comprises the following sequence of operations:
Loading. At a predetermined position falls lower punch. At this time, the upper punch is in its uppermost position, as the die aperture is positioned below the funnel. The loading device consists of a rotary engine still mounted on the machine bed and feeder metering hopper, hopper, which provides a continuous flow of material to be tableted. Tableting bad bulk materials for uniform feed-hopper bins can be supplied with screws, tedders, stirrers. For dispensing and directions to nip tablet mass feeder designed dispenser.
Compacting. When the matrix filled with the rotation of the socket countertops passed funnel, the upper punch is gradually lowered and, reaching the opposite side, falls immediately under the pressure roller. Another roller simultaneously exerts pressure on the lower punch.
Popping pills. The upper punch passing between the rollers starts climbing up, while the lower punch too little sitting up, pushing out of the nest ready tablet matrix. When using a scraper (knife) tablet with a countertop reset the receiver.
All press tools rotary machines (die and punches) consistently perform such movements. To ensure the proper movement of punches to the arms (sliders) are mounted rollers to help crawl punches (rolling) in Kapiri (upper and lower guide).
While downloading material roller upper arm with a punch located in stage I - the highest point of the upper Kapiri, then slips on his slant. Concerning the matrix hole punch is immersed in it and presses the material to be tableted. The pressure force increases, and reaches a maximum when the roller arm is pressurized roller - this pressing operation stage II. Then clip the punch up the Kapiri up and reaches a maximum. At the same time the lower slider committed such movements: roll punch bolstering on loading.
The volume of data is governed by the matrix holes roller. Movement of the lower slider is carried out by direct Kapiri whose roller rises squeezing rolls during pressing. This helps to ensure that the lower punch exerts pressure with his hand on the tablet mass. Then Kapiri few coming up, and the result is pushed lower punch tablet - Stage III ejection operation. Then drops down as the lower punch, due to lowering Kapiri, and the whole cycle repeats again movements.
Domestic rotary tablet machine characterized by the following features: the equipment may be in the rotor from twelve to fifty-five positions (matrices), machines can be equipped with one or two hoppers (single and dual). In the case of twin-machine, its performance is significantly increased, as the entire production process is carried out in a half-turn of the rotor.
An example of such a high-performance machines can lead dual-stream RTM-41, which has forty one pair of molds. This rotary engine enables tablets with diameters ranging from five to twenty millimeters. Release tablets for small diameter cylindrical shape with flat ends and spherical rotary machine used kim-300M.
Since in a rotary tabletting machine and the two-sided pressure increases and decreases gradually, the produced tablets are of high quality. In operation, these machines do not raise dust and operate smoothly. Also, the agitator may be set in the hopper. Be installed in the rotating rotor dusting device before and after loading matrix holes to pollinate surface filled matrix. Some designs include brushing or wiping devices for purification, which ensure the purity of the press tool.
The domestic industry also produces vibratory feeder equipped with rotary press machines. This device is capable of using the frequency and amplitude of oscillations of the vibrating feeder filling break cohesive strength of the material particles, which significantly increases the mobility and compensates for the lack of free-flowing powder. Equipped with vibratory feeder machines are characterized by high productivity. In this granulation is also needed, but the requirements for uniformity granulate somewhat reduced.
Domestic tablet presses allow you to control a lot of pills and possible mechanical inclusions during tableting. For these purposes, equipment is equipped with automatic devices, for example, the warning light turns on when a deviation from a given weight of the tablets, for automatic control on metal parts used a device that detects and removes pill with metallic inclusions from the stream. Dust remover tablets (dedustery) are used to remove dust from the surface of the fractions emerging from the tablet press. Passing through a perforated rotating drum, tablets cleaned from dust by means of special exhaust devices.
Tabletting process drugs typically occurs at pressures of from 25 to 250 mPas, is rarely applied higher pressure.
The technical aspect of rotary tablet machine far superior eccentric machines, but there are some disadvantages, such as:
complexity of the design;
requires more spare molds. Many factors affecting the quality of the tablets: pressing speed, the pressure, wear and condition of the press tool undergoing fairly heavy wear due to large loads. Chemical interaction tabletting masses with a matrix material, a rigid loading matrix, wall friction tableted matrix material particles contribute to the fact that the wear resistance of the matrix in two or three times less than the relative punches;
training equipment to the process of pressing more complicated;
cleaning equipment takes more time and effort;
the use of dozens of sets of molds a large variation in the deviation from the nominal mass, unlike eccentric machines where only one set of molds and weight fluctuation smallest separate tablets.
Given the shortcomings described, it can be concluded that the cost-effective only when the RTM mass production.
Prior to the beginning of the pressing process to configure, align and adjust optimally any tableting machine. Primarily carried out trial tableting. Equipment is started manually and seek to remove external flaws tablets required mass disintegration permissible and proper strength. For example, damaged and uneven surface of the tablet says that tabletiruemyh mass sticks and it lacks of lubricants, as well as the pressing surfaces are smooth enough. The diameter of the punches used to create the pill edge.
In that case, if the detected knocked tablet surface, it is necessary to adjust the position of the lower punch, as it rises high enough. Disintegration of tablets by throwing indicates that it is necessary to increase the pressure pressing, or more than the number of binders add tabletiruemoj weights. Conversely, too high a pressure results in delamination of tablets. The same thing can happen when you use too dry granulate.
Possible defects in the tableting process the tablets:
Insufficient mechanical strength tablets - small press pressure, poor concentration binders, adhesives and lubricants, poor ductility substances.
Poor-quality coating of tablets. Coating the tablets is improved with increasing the plasticity, which is added to the microcrystalline cellulose.
Adhesion (bonding). If the adhesion between particles tabletiruemoj weights are lower than the punch, the particles stick to the substance of press tools. High humidity can cause mass damage to the machine upon adhering to the upper punch. Also, high humidity and inadequate number of disintegrating agents lead to bonding mass. Rubbing beyond measure. Excessive rubbing tabletiruemoj weights can lead to parts of the matrix bonding, it reduces the weight of the tablets is not formed and glossy surface.
Shelf life is reduced - a possible result of the use of inaccurate amounts of auxiliary substances (binders, disintegrants, wetting), and the lack of pressure that eventually leads to defective exposed active substances. Inaccuracy dosage. If the tablet mass does not have sufficient fluidity occurs uneven filling of the matrix. Optimization of the particle size or the addition of an auxiliary agent such as aerosil, for example, allows to eliminate this drawback. Consequently avoid defects during tabletting, it is necessary to select the optimum parameters for each particular case.

There are no resource except the website www.Tabletpress.ru, which have been collected such detailed info on the production of tablets.