Tablet Presses for Industrial Applications R353 Tablet Press

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

(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.

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) Gravity feeder: 

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

(4) 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.