Press rotary

The Bucher-Guyer horizontal rotary press is a highly automated batch process machine that requires no press aid. The press consists of a horizontal hydrauhc ram inside a rotating cylinder containing many flexible rods covered with a knitted synthetic fabric. The rods have serrated surfaces to allow juice which passes through the fabric to flow to the discharge ends. Hydrauhc pressure is apphed for a preset time, the ram is retracted, and the cylinder is rotated to break up the press cake. This cycle is repeated several times before the press cake is removed from the cylinder and the press is cleaned (16). Juice yield for this horizontal rotary press is 84% with secondary water addition it is increased to 92% (15). 

After pressure appHcation, the top punch is removed and the compact is ejected from the cavity by the bottom punch. The cavity is then refilled and is ready for another charge. This cycle is repeated automatically at a rate that varies with the part and size and the complexity and dowabiUty of the powder. Pressing equipment producing relatively small, simple parts can operate at up to 200 parts/min. Rotary presses with multiple die sets are even faster. Table 5 gives the ranges of pressures used for various materials during die compaction. 

Single-punch machines produce approximately 100—150 tablets per minute. Depending on numbers of die per punch units, standard rotary presses can produce 5000 tablets/min, and even more with a double-sided rotary press. The newest high speed presses can achieve 12,000 tablets/min. 

Letterpress is printed directly by the rehef method from cast metal or plates on which the image or printing areas are raised above the nonprinting areas. Ink rollers apply ink to the surface of the raised areas, which transfer it directly to paper. Flat-bed cylinder presses are available but most letterpress is printed on rotary presses. 

Those with several stations of tooling— multistation (or rotary ) presses... 

Figures 15 and 16 provide a summary of the compression cycles for rotary and single-punch tablet presses. The formation of the tablet compact in these two types of presses mainly differs in the compaction mechanism itself, as well as the much greater speeds achieved with rotary type presses. The single punch basically uses a hammering type of motion (i.e., the upper punch moves down while the lower punch remains stationary), while rotary presses make use of an accordion-type compression (i.e., both punches move toward each other). The former find their primary use as an R D tool, whereas the latter, having higher outputs, are used in most production operations.

In building B-46, three separate operations are performed consolidation, demachlnlng, and cone swagglng. A rotary press Is used to consolidate A-5 explosive Into a grenade. To pick up the dust from this pressing operation, flexible rubber hoses (2.0 in.) are used. These lines are then connected to a stainless steel line that runs Into a wet collector. 

Although pellets for exptl use are loaded by single operation methods in which weighed charges are pressed either by stop loading or by controlled pressure techniques, quantity production of pellets is accomplished in automatic pelleting machinery, in which the explosive is metered volumetrically by the controlled movements of punches. Single stroke presses of the types used for expls produce about 90 pellets per minute while rotary presses have rates of about 700 pellets per minute... 

The details of instrumentation for tablet presses is thoroughly described in several texts and review papers [1,2,9,10] and will not be repeated here. The concepts, however, are important. The first and most important result of the instrumentation results in a plot of force vs. time (see Fig. 1). This shows the maximum force (or pressure) used for compaction of a tablet and such plots become even more important on a rotary press, when this measurement can be made on each tablet produced. 

Strain rate sensitivity of (or the effect of press speed on) the formulation is of primary concern in scale-up. Whether the product development work was performed on a single-stroke press or a smaller rotary press, the objective in operations will be to increase efficiency, in this case the tablet output rate and, therefore, the speed of the press. For a material that deforms exclusively by brittle fracture, there will be no concern. Materials that exhibit plastic deformation, which is a kinetic phenomenon, do exhibit strain rate sensitivity, and the effect of press speed will be significant. One must be aware that although specific ingredients (such as calcium phosphate and lactose) may exhibit predominately brittle fracture behavior, almost everything has some plastic deformation component, and for some materials (such as microcrystalline cellulose) plastic deformation is the predominant behavior. The usual parameter indication is that target tablet hardness cannot be achieved at the faster press speed. Slowing the press may be the only option to correct the problem. 

Mix all components, sieve and press on a rotary press to tablets with low compression force. 

Perhaps the most successful of the mechanised systems, to date, has been the horizontal rotary press designed and developed by a Swiss... 

Figure 3.4 Horizontal rotary press Universal Fruit Press HP5000 (Bucher-Guyer).

A small rotary press is most likely used when the initial formulation and process is developed at small scale. However, a large rotary press, used in a production area, may have significant differences in the number of stations, dwell time, and compression speed compared with smaller compression machines. Thus, early formulation design should consider the performance requirements of commercial production. Compaction simulators provide a useful tool able to reproduce the punch speeds of production machines and require only small quantities of powder blends for testing.86 The simulators can play an important role in formulation and process development and can also facilitate the technical transfer from development to commercialization. 

Gas flames have been used on rotary presses. Gas also has been used with some exotic materials requiring very high temperatures [over 2000F (1,093C)]. 

The basic unit of any tablet press is tooling consisting of two punches and a die, called a station. The upper and lower punches come together in the die that contains the tablet formulation. Principally, two different types of machines are used, the eccentric and the rotary press. The eccentric press produces about 50-130 tablets per minute. The rotary press has a multiplicity of stations arranged on a rotating table with the dies. A few or many thousands of tablets can be produced per minute. There are numerous models of presses, manufactured by a number of companies, ranging in size, speed, and capacity. 

On a rotary press the filling of the die and the following compression process is done at the same time at different stations. The compression is carried out in the simplest case with two rolls touching the upper and lower punches and compressing the powder mixture. In contrast to the eccentric press, the upper and lower punches exert pressure on the tablet mixture from both sides at the same time. 

Tablets compressed on a rotary press generally show a more consistent hardness when the upper and lower sides of the tablets are compared, where the upper side of tablets compressed on an eccentric press is usually harder than the lower side [3],...

Another reason, to use a rotary press rather than an eccentric press for tablet compression is the dwell time is usually shorter on a rotary press (see Figure 3). 

A direct correlation between the results of an eccentric press and a rotary press cannot always be drawn. In addition there are many different tablet presses with different settings and possibilities. These problems can be overcome by using a compaction simulator early in the development stage. An advantage of such a simulator is its versatility, that is, all types of presses can be simulated with small amounts of solid. The problem, however, is that such a simulator is very expensive. 

Manufacture by Direct Compression All the components were mixed for 10 min, passed through an 0.8-mm sieve, and compressed into tablets on a rotary press with a rate of 40,000 tablets/h at a compression force of 15-kN. Core shape was convex with a diameter of 9 mm and the engraving BASF. Hardness of the tablets was about 60 N. 

Jahn,T., and Steffens, K.-J. (2005), Press chamber coating as external lubrication for high speed rotary presses Lubricant spray rate optimization, Drug Dev. Ind. Pharm., 31(10), 951-957. 

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