WO2011061564A1

WO2011061564A1 - Rotary tablet press comprising a compaction unit and an associated method

Info

Publication number: WO2011061564A1
Application number: PCT/IB2009/055217
Authority: WO
Inventors: Jurgen Boeckx; Ivo Van Den Mooter; Jan Vogeleer
Original assignee: Gea Courtoy Nv
Priority date: 2009-11-20
Filing date: 2009-11-20
Publication date: 2011-05-26

Abstract

The rotary tablet press comprises a rotary turret (12) defining an axial direction and including a die disc (15) provided with a number of dies (16), a feeding device being provided for the supply of material to the dies, where each die is associated with at least one punch (17, 18). The punch has first and second ends, where the second punch end is receivable in the die and arranged for interaction with the material in the die. A compaction unit (21) is associated with the at least one punch, wherein the compaction unit includes a high velocity compaction, HVC, ram unit.

Description

Rotary tablet press comprising a compaction unit and an associated method

Field of the invention

The present invention relates to a rotary tablet press comprising a rotary turret and a compaction unit. The invention furthermore relates to a method for processing a material in a rotary tablet press.

Background of the invention

The act of compacting or compressing powders such as magnesium or iron based powders and other materials into high density pellets or more complex parts for use in e.g. the automotive and pharmaceutical industries, is known in the art. In order to obtain a higher structural integrity, like a higher density, the powder or mixture is e.g. pre- compacted, pre-heated, the compacting pressure may be changed etc.

Compression of powders can be performed in a rotary tablet press. Here a turret comprising a number of dies rotates and punches compress the powder in each die one after another. However this type of press is only able to provide a limited structural integrity, like a limited density in comparison with other methods.

As a consequence of the limited density the tablets can be less strong and as a consequence can have a lower tablet hardness, a lower crushing strength or can be prone to other structural failures, like capping or laminating.

As another consequence of the limited density the tablets can be more prone to shrinkage and/or deformation during a subsequent sintering. This means that the tablets need to be reworked or grinded in order to obtain an acceptable product in particular fields of application of the rotary tablet press.

To make sure the tablets have sufficient hardness or crushing strength, sometimes additional substances are added to the tablet formulation, like binders, or high quality and hence high priced substances are needed, to improve the hardness or crushing strength.

Sometimes the tablet press turret speed needs to be reduced, to make sure long enough compression time is attained to compress the tablets, and as a result attain sufficient tablet density.

A higher density tablet may be obtained by other means. An example of this is a single punch tablet press like a High Velocity Compac- tion (HVC) press. The two documents mentioned below disclose methods of producing higher density tablets.

WO0238315A1 describes a method of preparing high density products, in which a mould is filled with a powder having irregular powder particles; the powder consists of alloyed iron-based powders and es- sentially pure iron powders. Then the powder is subjected to HVC compaction with a uni-axial pressure movement at an impact ram speed above 2 m/s. The tablet is subsequently sintered. The compaction is preferably performed at ambient temperature or slightly elevated temperature. The method is particularly useful for producing large compacts above or about 2 kg.

A further way of producing a high density product is described in US20080202651. By subjecting a pre-compacted and pre-sintered body to HVC at an energy density of 1.8 MJ/m2 or more a high density compact is created. Preferably, a ram velocity of 2 m/s or more is used. The high density is obtained by only striking the subject once.

However, these methods have some disadvantages, when it comes to efficiency in terms of production rates. A single punch tablet press produces in general between 1-60 tablets per minute, while rotary tablet press produces from 60-15,000 tablets per minute.

Summary of the invention

An object of this invention is to overcome the above disadvantages.

In a first aspect of the invention, this and further objects are met by a rotary tablet press comprising a rotary turret defining an axial direction and including a die disc provided with a number of dies, a feeding device being provided for the supply of material to the dies, each die being associated with at least one punch, the punch having first and second ends, the second punch end being receivable in the die and ar- ranged for interaction with the material in the die, a compaction unit associated with the at least one punch, wherein said compaction unit includes a high velocity compaction, HVC, ram unit.

By using a rotary tablet press instead of a single punch tablet press a much higher rate of production is obtained.

Furthermore, by applying a single stroke in a rotary tablet press a higher quality tablet with better structural integrity, like a higher density is obtained than would be obtainable in a conventional rotary tablet press.

By attaining a higher density, a higher tablet hardness or a higher crushing strength can be reached.

In addition tablets with less structural failure, like capping or laminating, can be made.

In addition, if the tablets are to be sintered subsequently, less shrinkage and/or less deformation of the tablets during sintering is achieved by applying HVC. This results in less reworking or regrinding after compaction and/or sintering. Thus the tablet is "near net shape".

Moreover, a more homogeneous density of the tablet is obtained, which will lead to less weak planes in the tablet and again less capping or laminating. Additionally, other undesirable properties and failure risks are reduced as well.

Moreover, less additional substances, like a binder, are needed, or less high quality, and hence high priced substances are needed, to attain the desired hardness.

Moreover, the tablet press turret speed does no longer need to be reduced or need to be reduced less, again to attain the desired hardness.

In this way, powders with poor compaction properties, this is powders where it is very difficult to attain the desired tablet structural strength, can be made into tablets without tablet structural failures.

In one embodiment the compaction unit comprises a compression roller and a compression roller yoke, and the HVC ram unit includes a ram interacting with the compression roller yoke. This makes it possible to use the HVC ram unit in cooperation with a conventional rotary tablet press, as well as using the rotary tablet press without the HVC ram unit, when e.g. the HVC ram unit is retracted to its upper position.

In a preferred embodiment the compaction unit further comprises an air piston. The air piston allows the compression roller yoke to be lifted and allows the compression roller yoke to be subjected to a ramming action from the ram unit, with the ramming action transferred to the compression roller, the punch and further to the tablet. If not, the ramming action will be performed on the compression roller yoke dead stop or the compression roller yoke frame structure.

As an alternative to the air piston, the compression roller yoke could be supported by a spring or a hydraulic piston.

In a further embodiment the HVC ram unit comprises a ram and a transition punch interacting with the first punch end. A transition punch can typically be made stronger than a compression roller, because no bearings are needed, which typically are placed between the compression and the compression roller axis. Hence, by using a transition punch much higher impact loads, generated by the HVC ram, can be used. A transition punch has also a less complex mechanical structure than a compression roller plus a compression roller yoke, which allows the embodiment with the transition punch to be simple, robust and very cost effective.

In another embodiment the HVC ram unit comprises a ram that interacts directly with the first punch end. This provides for a mechanically simple structure, even more simple than the embodiment of the transition punch, which allows for an even more robust and cost effective solution.

Advantageously, the ram is a hydraulic ram, which combines well-defined properties as regards reliability of operation with sufficient ram energy. Other types of rams may also be used, such as a pneumatic ram, a spring loaded ram or a ram operated by means of explosives.

Each die of the rotary tablet press may also be associated with two punches, each punch being associated with a respective compaction unit. By using two compaction units and two punches, one at the top and one at the bottom, respectively, full symmetrical compaction is ensured. This in turn ensures symmetrical (vertical) density gradients within the tablet, with the neutral line, the horizontal line of minimal density in the middle of the tablet. A symmetrical compaction with the neutral line in the middle results in minimal deformation of the tablet after ejection. It also ensures minimal shrinkage when tablets are sintered and in turn less potential reworking or grinding. In this embodiment, the number of ram units may be one or two.

Furthermore, the rotary tablet press may comprise at least one pre-compression station and at least one main-compression station, where the HVC ram unit is provided at the main-compression station. By pre-compressing the material, air is driven out of the tablet, which results in even higher densities.

Furthermore the pre-compression station may be provided with a HVC ram unit as well.

In a further embodiment the HVC ram unit may be located at the precompression station only.

The rotary tablet press may further comprise a measurement device for measuring at least one parameter of the tablet manufactured in the rotary tablet press and a control device for regulating the energy per stroke of the ram unit. The at least one parameter could be a weight parameter. Single stroke presses as well as rotary presses are known for their weight control system, either based on measurement of compression force or displacement. The individual tablet weights can be used to individually control or set the ram energy. For a heavier tablet more ram energy can be used and for a lighter tablet less ram energy may be used. The net result is less variation on the tablet density and a reduced influence of tablet weight variation on tablet density variation. Aside the individual tablet weights, also the mean tablet weight could be used to control or set the ram energy.

The at least one parameter could also be tablet thickness and/or porosity. Tablet porosity can be measured at the compression station, by measuring the tablet thickness at the compression. This is the so-called "in die porosity". This differs slightly from the out of die porosity, due to the elastic expansion of the tablet after compression or after ejection. Equally a number of measurement concepts are possible to measure the tablet porosity after ejection, such as thickness measurement, both with contact or contactless, optical spectroscopy such as NIR spectroscopy, tablet capacitance measurement, etc.

Using the measured tablet porosity, the hydraulic ram energy could be used to set or adjust and control the mean tablet porosity.

In a number of applications, the tablet porosity is of high importance. For instance, for pharmaceutical tablets, it is known that there is a good correlation between tablet porosity and tablet dissolution. For sintered tablets, it is known that the tablet porosity will determine the tablet shrinkage and/or deformation during sintering. So by reducing porosity during production less reworking and grinding is required.

The material to be processed in the rotary tablet press may furthermore be a powder or a granular material, for instance a nuclear fuel powder. Depending on the purpose of the rotary tablet press, different materials, such as pharmaceutical powders, metal powders or nuclear fuel powders may be used.

The at least one punch may be made out of a material with an increased stiffness, such as a ceramic material, powder metallurgic ma- terial or the like. Due to the elasticity of both the compression station (top and bottom) and/or the punches (top and bottom) a part of the energy of the hydraulic ram is converted into elastic deformation energy, which is in turn converted into heat. The part of the energy of the hydraulic ram that is converted into heat, due to the elastic deformation, does not result in a densification of the tablet and is thus lost energy. As such it is beneficial to make both the compression station(s) and the punch(es) as stiff as possible, by designing a stiff construction of the punch(es) and/or compression station or by using a stiff material.

According to a further design the rotary tablet press machine structure is dampened. This is done out of consideration to the surroundings as the impact of HVC ram unit is prone to strong vibrations and loud noise. By dampening the machine structure a reduction in both the vibrations to the surroundings and the noise level of the machine is achieved. The rotary tablet press may further comprise a reciprocating feeder. A reciprocating feeder is formed as a powder feeding shoe, moving back and forth over the die(s). This type of feeder is known to give more segregation than the rotary paddle feeder of a typical rotary press. Other feeder means are conceivable, for instance a rotary paddle feeder.

According to a second aspect of the invention a method for processing a material in a rotary tablet press is provided. The method comprises the steps of: providing a die disc with a number of dies, providing a feeding device for the supply of material to the dies, associating each die with at least one punch, said punch having first and second ends, said second punch end being receivable in the die and arranged for interaction with the material in the die, associating a compaction unit with the at least one punch, the compaction unit including a high velocity compaction, HVC, ram unit, and subjecting the material in the die to high velocity compaction, HVC, by means of an impact provided by the HVC ram unit.

Moreover, a more homogeneous density of the tablet is obtained, which will lead to less weak planes in the tablet and again less capping or laminating. Additionally, other undesirable properties and failure risks are reduced as well. Moreover, less additional substances, like a binder, are needed, or less high quality, and hence high priced substances are needed, to attain the desired hardness.

According to an embodiment the step of associating the compaction unit with said at least one punch is carried out by synchronising the operation of the HVC ram unit with the position of the punch. By synchronizing the operation or movement of the HVC ram unit with the position of the punch, it is ensured that the punch is located directly un- der the ram unit. Other means such as a roller yoke or a transitional punch may be located between the punch and the HVC ram unit.

According to an embodiment the synchronising is performed using an encoder on a central axis of the turret to indicate the position of the punch.

According to another embodiment the synchronising is performed using a stationary sensor to indicate the position of the punch.

The rotational speed of the rotary tablet press may be controlled such that at the association of the compaction unit with the punch, the speed of the rotary turret is sufficiently low so as to allow the impact to be performed. By controlling the speed it is possible to both adjust the production speed as well as the length of the impact.

The speed may also be set at a predetermined low constant level. In this way no variation of the speed during rotation of the turret is required, but instead a constant flow is obtained, i.e. avoiding start and stops of the rotary tablet press.

The speed may also be varied such that the level of the speed is reduced momentarily when the impact is performed. By lowering the speed the length of the impact may be extended, thus increasing the compaction energy density. When the position of the HVC ram unit is in between punches, the speed may be increased in order to increase the production rate of the process. The press may also even be intermittently stopped with the punch or punches is/are under the compression roller. After the compaction has been performed the turret is again ro- tated.

According to a preferred embodiment the pre-compression of the material is carried out in at least one pre-compression station and compaction is carried out in at least one main-compression station. By pre-compressing the material, air is driven out of the tablet, which re- suits in even higher densities.

According to another design the pre-compression is carried out by vibration of the material. By vibrating the material, such as a powder, more air escapes from the material thus reducing the risk of subsequent capping.

The at least one parameter of the tablet manufactured in the rotary tablet press may be measured and the energy per stroke of the ram unit may be regulated in accordance with the result of the measurement. The at least one parameter could be a weight parameter or a density. By regulating energy according to tablet weight, the net result is less varia- tion on the tablet density and a reduced influence of tablet weight variation on tablet density variation.

The at least one parameter could also be tablet thickness and/or porosity. Using the measured tablet porosity, the hydraulic ram energy could be regulated, according to the tablet porosity, which will result in a reduced tablet porosity variation.

Using the measured tablet thickness, the hydraulic ram energy could be regulated, according to the tablet thickness, which will result in a reduced tablet thickness variation.

The measurements could be performed either as a general indi- cator for a whole batch or the measurements are carried out on the individual tablets and a feedback loop is provided in order to adjust the energy to the individual tablet.

Aside the individual tablet weights, also the mean tablet weight could be used to control or set the ram energy. According to another design the HVC is performed as a cryogenic compaction. Cryogenic compaction, a compaction with strong cooling of the powder before and/or during compaction, will, for particular powders, give even more dense tablets. The cryogenic compaction may be performed as a separate step in addition to the HVC.

According to another design the HVC is performed as/after hot compaction. Hot compaction is where the powder is heated before and/or during compaction to just below the melting point. This will typically be within the temperature range were plastic deformation is pro- moted. This will give even more dense tablets.

According to another design the HVC performs a coining operation. With coining a tablet is re-inserted in the die, and undergoes again a compression step to further densify the tablet.

Any feature from the first aspect may be combined with any feature from the second aspect.

Brief description of the drawings

In the following the invention will be described in further detail by means of examples of embodiments and referring to the schematic drawings, in which

Fig. 1 shows a perspective view of a rotary tablet press according to the invention, in a first embodiment;

Fig. 2 is a view similar to that of Fig. 1 showing the rotary tablet press of Fig. 1, however with some details in another position;

Fig. 3 is a side view, on a larger scale, of the rotary tablet press shown in Figs 1 and 2, in a first position;

Fig. 4 is a side view, on a larger scale, of the rotary tablet press shown in Figs 1 and 2, in a second position;

Fig. 5 is a side view, on a larger scale, of the rotary tablet press shown in Figs 1 and 2, in a third position;

Fig. 6 is a side view, on a larger scale, of a second embodiment of the rotary tablet press according to the invention;

Fig. 7 is a side view, on a larger scale, of a third embodiment of the rotary tablet press according to the invention; Fig. 8 shows the rotary tablet press according to a fourth embodiment according to the invention; and

Fig. 9 shows a diagram of the relationship between time and rotational speed of the rotary tablet press.

Detailed description of the invention and of preferred embodiments

Fig. 1 shows a rotary tablet press 1 for compression of a feedstock in the form of powder or granular material into tablets, compacts or the like. The press according to the invention may be a so-called in- dustrial press employed in the production of a variety of different products, such as vitamins, nutritional supplements, food, pet food, detergents, salts, explosives, ceramics, batteries, balls, bearings, and in particular nuclear fuels. For compressing or compacting the products a compaction unit 21 is provided, this unit will be described in further de- tail below.

The rotary tablet press 1 has a press housing 2 comprising a frame 3 and an outer lining 4. The press housing 2 is composed of three sections, which are located on top of each other and are separated by means of partition walls. The lower section, designated the drive section 5, is separated from a central section, designated the compression section 6, by a bottom frame 7 of the press, and the compression section 6 is separated from an upper section, designated the accessory section 8, by a top frame 9 of the press. There is an outer lining over the upper section 8 as well (not indicated as such). Two vertical support rods 7a and 7b (shown in Fig. 1 only) extend between the bottom frame 7 and the top frame 9.

The drive section 5 comprises a not shown electrical drive motor having a suitable transmission for driving a vertical drive shaft projecting up through a central opening in bottom frame 7 and having at its upper end a coupling part for detachable connection with a rotary turret 12 located in the compression section 6 of the press housing 2 in a position of use of the rotary tablet press 1.

In the embodiment shown in Fig. 2, the rotary turret 12 of the rotary tablet press 1 defines an axial direction, and includes, in a manner known per se, for instance from Applicant's published international application No. WO 2009/112886 or other rotary tablet presses known in the art, a die disc 15 provided with a number of dies 16 or bores fulfilling the function of dies, that is receiving and containing the material to be com- pressed or compacted. A feeding device is provided for the supply of material to the dies 16, and each die 16 is associated with at least one punch, in the embodiment shown a top punch 17 which is guided in a top punch guide 19. The top punch 17 has first and second ends 17a, 17b, of which the second punch end 17b is receivable in the die 16 and arranged for interaction with the material in the die. In the embodiment shown, a bottom punch 18 is provided as well, the bottom punch 18 being guided in a bottom punch guide 20.

In order to compact the material fed into the dies, a compaction unit 21 is associated with said at least one punch 17, 18. In the em- bodiment shown, the compaction unit 21 is located in the accessory section 8 of the rotary tablet press 1. According to the invention, the compaction unit includes a high velocity compaction, HVC, ram unit 22.

Referring now in particular to Figs 3 to 5, a sequence of operational steps of a rotary tablet press according to the invention will be de- scribed in further detail. In the embodiment shown, the rotary tablet press 1 comprises a compaction unit 21 provided with a compression roller 24 and a compression roller yoke 25. The HVC ram unit 22 includes a ram 23 interacting with the compression roller yoke 25. In the embodiment shown, the compaction unit 21 further comprises an air pis- ton 26. The air piston 26 has the function of lifting the compression roller yoke 25 to allow for a compression stroke, i.e. a compression movement, to take place when the ram unit 22 performs its operation.

In Fig. 3, the ram 23 is in its upper position and the compression roller yoke 25 is lifted from its dead stop, i.e. from its abutment with structure 27 surrounding the air piston 26, by the air piston 26.

In Fig. 4, the ram 23 subjects the compression roller yoke 25 to an impact, the impact being in turn transmitted to the compression roller 24 and further to the first punch end 17a of the punch 17 as shown in Fig. 5. The operational steps will be described in further detail below, in connection with the description of the method according to the invention.

A compression roller yoke is the standard embodiment of a traditional rotary tablet press. Using the roller yoke allows for integration of a HVC ram unit onto an existing rotary tablet press. Having a compression roller yoke also allows the rotary tablet press to be used without the HVC ram unit, i.e. as a traditional rotary tablet press performing compression of the material in a conventional manner.

In a second embodiment, shown in Fig. 6, elements having the same or analogous function as in the first embodiment shown in Figs 1 to 5 carry the same reference numerals to which 100 has been added. Only differences from the first embodiment will be described in detail. In the second embodiment, the rotary tablet press comprises a compaction unit 121, of which the HVC ram unit 122 comprises a ram 123 and a transition punch 130 interacting with the first punch end 117a of the punch 117. A transition punch could be built bigger and stronger than a punch with a stronger guiding that withstands any lateral forces from the ram unit. It thereby prevents any strong lateral ram unit forces onto the punches.

In a third embodiment, shown in Fig. 7, elements having the same or analogous function as in the first embodiment shown in Figs 1 to 5 carry the same reference numerals to which 200 has been added. Only differences from the first embodiment will be described in detail. In the third embodiment, the rotary tablet press comprises a compaction unit 221, of which the HVC ram unit 222 comprises a ram 223 that interacts directly with the first punch end 217a of the punch 217.

In a fourth embodiment shown in Fig. 8, elements having the same or analogous function as in the first embodiment shown in Figs 1 to 5 carry the same reference numerals to which 300 has been added. Only differences from the first embodiment will be described in detail. In the third embodiment, the rotary tablet press comprises a second compaction unit 331, of which a second HVC ram unit 332 comprises a second ram 333 that interacts directly with the second punch end 318a of the second punch 318. The second HVC ram unit 332 may also be con- structed as the embodiments in Figs 5 or 6, i.e. by placing either a roller yoke or a transitional punch in between the HVC ram unit and the punch.

Fig. 9 shows a diagram of the different speed patterns that may be applied to the rotary turret of the rotary tablet press. The rotational speed of the rotary tablet press may be controlled in any suitable manner to ensure proper compaction of the tablets to be produced. One manner of controlling the speed is such that at the association of the compaction unit with the punch the speed of the rotary turret is suffi- ciently low so as to allow the impact to be performed. For instance, the speed may be set at a predetermined low constant level indicated by line a. Another option is to reduce the level of the speed momentarily when the impact is performed as indicated by line b. A third option is to stop the press intermittently while performing the stroke, such as indicated by dashed line c.

In all of the above embodiments, the ram may be activated in any suitable manner. However, preferably, the ram is a hydraulic ram.

It is also conceivable to associate each die of the rotary tablet press with two punches, each punch being associated with a respective compaction unit, cf. Fig. 8.

The rotary tablet press may comprise at least one pre- compression station and at least one main-compression station, said HVC ram unit being provided at the main-compression station. Other configurations are of course conceivable; for instance, the ram unit may be used at pre-compression only, or both at pre-compression and main- compression.

In order to control the rotary tablet press, the press may comprise a measurement device for measuring at least one parameter of the tablet manufactured in the rotary tablet press and a control device for regulating the energy density of the ram unit.

As mentioned in the above, the material to be processed in the rotary tablet press may be any powder or granular material, for instance a nuclear material.

In the following, a method for processing a material in a rotary tablet press will be described in further detail. The method comprises the steps of providing a die disc with a number of dies, providing a feeding device for the supply of material to the dies, associating each die with at least one punch, said punch having first and second ends, said second punch end being receivable in the die and arranged for interaction with the material in the die, associating a compaction unit with said at least one punch, said compaction unit including a high velocity compaction, HVC, ram unit, and subjecting the material in said die to high velocity compaction, HVC, by means of an impact provided by said HVC ram unit.

The step of associating the compaction unit with said at least one punch may be carried out by synchronising the operation of the HVC ram unit with the position of the punch.

The synchronising may be performed using an encoder on a central axis of the turret to indicate the position of the punch. An en- coder is a widely use and easily available rotational position sensor, with excellent robustness and excellent measuring accuracy, and a compact build. It is also advantageous from an economic point of view.

Alternatively, the synchronising is performed using a stationary sensor to indicate the position of the punch.

In the case the rotary tablet press comprises one station for pre-compression and one station for main-compression, pre- compression of the material is carried out in at least one pre- compression station and compaction by means of the HVC ram unit is carried out in at least one main-compression station.

Feedback from the operation may be provided. Preferably, at least one parameter of the tablet manufactured in the rotary tablet press is measured and the energy density of the ram unit is regulated in accordance with the result of the measurement.

The invention is not limited to the embodiments shown and de- scribed in the above. Several combinations and modifications may be carried out without departing from the scope of the appended claims.

Claims

C L A I M S

1. A rotary tablet press comprising :

a rotary turret defining an axial direction and including a die disc provided with a number of dies,

a feeding device being provided for the supply of material to the dies,

each die being associated with at least one punch, said punch having first and second ends, said second punch end being receivable in the die and arranged for interaction with the material in the die,

a compaction unit associated with said at least one punch, c h a r a c t e r i z e d in that

said compaction unit includes a high velocity compaction, HVC, ram unit.

2. A rotary tablet press according to claim 1, wherein the com- paction unit comprises a compression roller and a compression roller yoke, and wherein the HVC ram unit includes a ram interacting with the compression roller yoke.

3. A rotary tablet press according to claim 2, wherein the compaction unit further comprises an air piston .

4. A rotary tablet press according to claim 1, wherein the HVC ram unit comprises a ram and a transition punch interacting with the first punch end .

5. A rotary tablet press according to claim 1, wherein the HVC ram unit comprises a ram that interacts directly with the first punch end .

6. A rotary tablet press according to any one of the preceding claims, wherein said ram is a hydraulic ram .

7. A rotary tablet press according to any one of the preceding claims, wherein each die of the rotary tablet press is associated with two punches, each punch being associated with a respective compaction unit.

8. A rotary tablet press according to any one of the preceding claims, wherein the rotary tablet press comprises at least one pre- compression station and at least one main-compression station, said HVC ram unit being provided at the main-compression station .

9. A rotary tablet press according to any one of the preceding claims, wherein the rotary tablet press comprises a measurement device for measuring at least one parameter of the tablet manufactured in the rotary tablet press and a control device for regulating the energy density of the ram unit.

10. A rotary tablet press according to any one of the preceding claims, wherein the material to be processed in the rotary tablet press is a powder or a granular material, for instance a nuclear material.

11. A method for processing a material in a rotary tablet press, the method comprising the steps of:

providing a die disc with a number of dies,

providing a feeding device for the supply of material to the dies, associating each die with at least one punch, said punch having first and second ends, said second punch end being receivable in the die and arranged for interaction with the material in the die,

associating a compaction unit with said at least one punch, said compaction unit including a high velocity compaction, HVC, ram unit, and

subjecting the material in said die to high velocity compaction, HVC, by means of an impact provided by said HVC ram unit.

12. The method according to claim 11, wherein the step of associating the compaction unit with said at least one punch is carried out by synchronising the operation of the HVC ram unit with the position of the punch.

13. The method according to claim 12, wherein the synchronising is performed using an encoder on a central axis of the turret to indicate the position of the punch.

14. The method according to claim 12, wherein the synchronising is performed using a stationary sensor to indicate the position of the punch.

15. The method according to any one of claims 11 to 14, wherein the rotational speed of the rotary tablet press is controlled such that at the association of the compaction unit with the punch the speed of the rotary turret is sufficiently low so as to allow the impact to be per- formed, or the speed is set at a predetermined low constant level, or the level of speed is reduced momentarily when the impact is performed, or the level of the speed is momentarily stopped when the impact is performed.

16. The method according to any one of claims 11 to 15, wherein pre-compression of the material is carried out in at least one pre-compression station and compaction is carried out in at least one main-compression station.

17. The method according to any one of claims 11 to 16, wherein at least one parameter of the tablet manufactured in the rotary tablet press is measured and the energy density of the ram unit is regulated in accordance with the result of the measurement.