Issue link: http://www.e-digitaleditions.com/i/477622
Tablets & Capsules March 2015 31 also reduce the number of tool setups required per batch. Fewer setups translate into more time spent making prod- ucts and faster batch times. These advantages lead to other benefits: Less energy usage and fewer hours to com- plete a campaign, which makes the press available for other products. Because run times are shorter, the cost of operating the tablet press also decreases. A less obvious benefit is the ability to quickly manu- facture time-sensitive granulations. These are formula- tions that—to prevent defects—must be compressed into tablets very shortly after they're prepared. Presses equipped with multi-tips are better suited to the task than conventional presses because they work faster. Plus, if the formulation requires a special environment, using fewer presses means less need for dedicated suites. One press, more production While those benefits are significant, most of the in quir - ies our company receives are driven by a desire to in crease production, preferably using an existing tablet press. One customer's inquiry concerned upgrading a Korsch PH800 that had 77 stations equipped with single-tip tooling. The machine's theoretical maximum output was ap - proximately 831,000 tablets per hour but, in reality, it ran at 80 percent of maximum speed, which is typical, and produced around 665,000 tablets per hour. To increase output, the press was equipped with double-tip punches and corresponding dies. During trials, tablet output increased to 1 million tablets per hour—approximately a 50 percent increase—while operating at 60 percent of its maximum speed. Next, the press was fitted with triple-tip tooling, and output reached nearly 1.5 million tablets per hour, a 125 percent improvement. As a result, the press could complete a batch in 8.5 hours instead of 14.5 hours. Another project involved a high-speed Fette tablet press equipped with a segmented die table. With single- tip tooling, it ran at 900 rpm and produced 900,000 tablets per hour. With the addition of double-tip punches and corresponding dies, the machine reached 1,200 rpm and output soared to 2.4 million tablets per hour. Tablet press compatibility Although most presses can accommodate multi-tip tooling, there are some factors to take into account. • Confirm that the upper turret has a keyway in its punch guides to align the tooling. It is not necessary to have a keyway in the lower guides because, as with standard tooling, the tips remain in the die. But it is advantageous to have a keyway there; it speeds setup and reduces the chance of damaging the lower tips. • Examine the feeder paddles. They may require mod- ification to ensure they deliver enough formulation to fill the dies. • Assess the tablet ejection system. It must be capable of receiving a larger volume of product. • Consider the press monitoring system and associated equipment. Everything must work in concert to pro- vide information efficiently, and some systems can- not accommodate multi-tablet output. • Check the condition of the press. There should not be significant wear in the turret area. Pay particular attention to the punch guides, keyways, and die pockets. Also inspect the cams and replace them if they show signs of excessive wear or degradation. Failure to do so will lead to damaged punch heads. Formulation considerations It's also important to assess the formulation's character- istics before you commit to multi-tip tooling. How well the granulation flows is key. If it doesn't flow into the die quickly enough, you're sure to have problems. There are a few ways to increase flow on the press without having to reformulate. One approach is to modify the feeder mechanism. The appropriate feeder will allow the press to maintain its turret speed. In other cases, run- ning the turret more slowly is the better approach because that gives the formulation more time to fill the dies. The formulation's particle size distribution is another important factor. If, for example, the percentage of fines is high, the same problems typical of presses running single- tip tooling can multiply. This includes fines passing through the clearance between the tip and die, which allows buildup and causes tightness and friction in the lower punch, possi- bly leading to premature headwear and damaged cam tracks. If the percentage of fines cannot be reduced, modi- fying the working tolerances may be a solution. It may also help to shorten the tip length and/or change the tip under- cut on the lower punch. Reducing the tip length decreases the amount of contact and thus friction, while a sharp undercut to the tip (sometimes called a Bakelite or die- scraper relief) can help keep the die bore clean. Tablet shape and size When considering multi-tip tooling, evaluate the shape and size of the tablet to ensure it is compatible. Round tablets allow an efficient arrangement of the tips, but capsule shapes, ovals, and polygons are more chal- lenging. They may require more time to devise an arrangement that preserves tooling robustness and opti- mizes die filling and tablet take off. To use multi-tip tooling, the tablet press must have a keyway in its upper punch guides to maintain alignment. It is advantageous, but not neces- sary, to have a keyway in the lower punch guides, too.