Rotary Tablet Presses for Industrial Applications R57 Tablet Press

Special design for MOX Pellet Production

The R57 design is the result of GEA's many years' experience in the nuclear fuel pellet industry. Besides the fact that this industry requires very reliable equipment, constant density compaction is essential to reduce the hour-glass shape effect on the sintered pellets.

Features & Benefits

  • Optimized pellet density control: automated in-line pellet density measuring with feedback to the press.
  • New high-performance powder feeding system.
  • Hold-up / hold-down system for smooth ejection and avoiding cracks in pellets.
  • High resistance to abrasive powders. 
  • Interfaces for glove ports.
  • Maximum efficiency set-up: main motor and gearbox are put next to the press, so they remain outside of customer's glove boxes.
  • Proven reliability, with presses in operation in a nuclear environment for over 40 years.
 

Technical Specifications

The R57 is available for five tooling sizes:

ModelR57-AR57-BR57-CR57-DR57-E
Number of stations2018161412
Max. compression force [kN]130
Max. fill depth [mm]55
Max. range / set of fill cams [mm]25
Max. top punch penetration [mm]16
Outside die diameter [mm]3540485670
Punch-holder body diameter [mm]2225404545
Max. output capacity [tab/h]38.40034.56030.72026.88023.040
Outlet height [mm]1.539
Press height [mm]2.030 to 2.600
Floor space [mm]1.150 x 1.660
Net weight [kg]3.000

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R57 Highlights

The R57 is available with a number of special features to improve and expedite the tablet production process and provide higher levels of control.

Tooling options

Punch holders with rollers

Special tooling features include multi-tip punches, core rods and high-pressure heads.

(1) Punch holders for high compression forces:

Generally speaking, pharmaceutical presses are equipped with standardized mushroom-head tooling, as compression and ejection forces are limited for small oral intake tablets. However, for industrial applications, higher compression and ejection forces are required. Once compression forces rise above 60kN, we strongly recommend the use of GEA's punch holder design for long lasting trouble-free compaction at the lowest cost. 

GEA punch holders are different from the EU or TSM standard in three ways:  

  1. The patented high-pressure heads are milled in such a way that the contact with the compression roller is a line, as opposed to the single point contact between a mushroom- head punch and the compression roller. The line contact reduces the specific pressure at the contact point considerably, resulting in a longer life time of the punch head.
  2.  As the punch holder is not subject to heavy wear, we always propose tooling split into two parts: the punch holder and the punch tip. In this way, both can be exchanged separately.
  3.  Rollers on the side of the GEA high-pressure head roll in a cam track compared to the friction movement of a mushroom-head in the cams. These rollers also allow for a longer dwell time at pre-compression and for smooth wear-free ejection.  

(2) Core rods:

Pellets with vertical holes are made using core rods held and centred by the lower punch. A central ring is positioned on the turret part between the dies and the lower punch guides. This ring is used to secure the core rod holder pins at the correct height. During the complete compression cycle the core rod remains flush with the die table surface. Whilst filling, the powder flows around the core rod into the die. Occasional powder remains on top of the core rod get wiped off by a scraper blade. A top punch with a central hole closes off the die and the pellet is compressed. Core rod material properties and surface finish must be carefully chosen to avoid rupturing of the core rod during pellet ejection.

(3) Multi-tip tooling:

To increase production output for smaller tablets, multi-tip tooling is one of the possibilities. A number of smaller punch tips are fastened on a larger punch holder. The production output is multiplied by the number of tool tips without changing the dwell or de-aeration time.

Powder in-feed options

Courtoy™ feeder inside tablet press

A number of features are available to improve the flow of powders with poor flowability and to ensure fragile powders are not damaged.

(1) Double-paddle feeder:

The double-paddle rotary feeder is, at present, the most used feeder type, because the time the die travels under the feeder is longer than with other feeder types. This enables faster tablet output speeds. The first paddle of the feeder is located above the overfill cam, while the second paddle is situated above the dosing cam recycling the powder back to the first paddle.

Advantages of the GEA double-paddle feeder: 

  • Independent drive for each paddle, with individual speed setting  
  • Light weight 
  • No sprockets or belts for transmission between paddles 
  • Easy to remove, open and clean 
  • Exchangeable paddle shapes for different powder characteristics 
  • Available with slide-in wear plate, allowing the feeder to make contact with the turret surface. This minimizes the quantity of powder outside the feeder, increasing yield. 

(2) Single-paddle powder feeder: 

Improves filling compared to a gravity feeder, with a minimum of energy input.  

(3) Vibra-fluid feeder: 

A vibratory device improves the flow of difficult powders.  

(4) Gravity feeder: 

For fragile powders, the gravity feeder can be the best option.  

(5) Small-dosage feeder: 

To avoid feeder jamming, a very precise measurement of the powder level in the feeder triggers the powder in-feed.  

(6) Powder dosing valve or PDV: 

Presses are often fed from IBCs or silos. As these run empty, the powder pressure in the press feeder and hence the die varies, resulting in tablet weight variations. The tablet weight control system on the press or the operator can adjust the die fill, but the PDV is a much easier way to keep the feeder pressure constant. A sensor detects the powder level in a transparent tube and controls the motor of the powder scraper. When the scraper does not rotate the powder flow stops. In addition to keeping the powder pressure constant, the PDV prevents powder segregation. Another advantage is that the PDV can be used with abrasive powders. 

(7) Powder agitator: 

The agitator is designed especially for powders with a tendency for bridging. A central rod with side bars rotates gently in the powder, breaking bridges.

 

Perfecting the ejection

Several solutions are available to make sure the pressed components are not damaged or deformed during ejection.

(1) Hold-up / hold-down system: 

This system prevents tablet lamination or capping due to a sudden pressure release during tablet ejection. A set of pneumatic cylinders can be adjusted in height, angle and force and maintain a force on the tablet during tablet ejection, which can be essential for ejection at high tableting speeds. The pressure can be identical in all cylinders or - optionally - set individually. All pressures are controlled by proportional valves and set on the operator interface. 

(2) Mitigating the impact of high ejection forces: 

When GEA punch holders with bearings rolling on cams are used, ejection forces up to 10kN can be sustained without excessive wear and tear. 

(3) Die wall lubrication:  

As a rule, lubricants enabling smooth ejection are blended into the powder. However, for some applications this is not an option, because most solid lubricants reduce tablet hardness or contaminate the powder. An alternative to adding a lubricant to the powder blend, the die wall lubrication system deposits a thin oil or grease film on the die wall to ensure smooth tablet ejection. A complete solution is available to control the amount of lubricant on the die wall.

(4) Punch face lubrication: 

When punch face sticking is a problem, a magnesium stearate film can be deposited on the punch faces.  

(5) Tablet take-off system: 

The tablet take-off replaces the standard tablet chute and is a great feature for removing fragile tablets from the press and/or bringing tablets on a single line for further processing. 

Process control

MODUL™ tablet press

(1) Air compensator for constant density compression

A top and bottom air compensator is installed when full symmetrical compaction is required. 

An air compensator, a feature exclusive to GEA tablet presses, is connected to both top and bottom compression roller and functions as a cushion. The pressure in the air compensator is set in such a way that during every pellet compression cycle, the rollers travel a few tenths of a millimeter, making sure that every compression is performed at the set compensator pressure. Every pellet will be pressed to equal density and height variations will reflect differences in die fill and powder property variations. 

(2) Air compensator for constant thickness compression

The pressure set in the compensator equals the maximum compression force the tooling tips can take. When the set threshold is crossed, the air compensator will move instantly and protect individual punch tips from overload. The press will stop and the overload position will be indicated. 

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