Compression press

In order to overcome such disadvantages the injection-compression process has been developed. A conventional compression press is coupled to a screw preplasticising unit which can deliver preheated and softened material direct to a compression mould cavity. 

Compression presses are produced in various sizes throughout the world. In general, shaft seals are manufactured on presses with platen sizes in the range of 350 X 350 mm to 715 x 715 mm with clamp loads in the range of 1500 kN to 4000 kN. 

Figure 18 shows a typical line of compression presses fitted with vacuum chambers. This type of press can be purchased with platen sizes in the range 355 x 355 mm to 710 x 710 mm. The choice of press size is dependent on product size, product design, and volume. 

Figure 18 A typical compression press molding line.

An injection machine and mould cost considerably more than a compression press and compression mould. The main economical advantages of injection moulding lie with long production runs and complicated mouldings. For short runs compression or transfer moulding may still be the most suitable process. 

Economies of production personnel can still be achieved today, and a unit cost reduction of 30-50% is possible. Physical properties of mouldings can be enhanced and the adhesion of the bond in a rubber-metal part is improved. Tool costs can be cheaper than for compression press methods because the throughput is greater. 

F.B. Wells, S-Trinitrobenzene as a Binder in Compression-Molded Explosive Compositions , PATR 4783 (1975) [It was found that the ideal HMX/TNB ratios required to provide compression-molded pellets that come close to the theoretical max d are 95/5 to 94/6 with no TNB loss at SOOOpsi compression press. It was also noted that the HMX used need not be of a very fine particle size to be successfully molded in the mixt] 54) J.R. Hendrickson F.B. Wells, Castable Composite Explosive Compositions Containing a Mixture of Trinitrobenzene (TNB) and Trinitroxylene , USP 3994756 (1976) CA 86, 75497 (1977) [A castable composite expl which meets Mil Specs is claimed which contains TNB 26.25, Trinitroxylene 3.75, and HMX 70 wt %] 55) F.B. Wells, High-... 

Reactive powdered resins and curing agents can be combined by dry blending. These powder blends can then be preformed into various shapes by dry compression pressing. 

Four basic methods are commonly used for the application of coating materials on drug tablets (1) pan coating, (2) fluidized-bed coating, (3) compression (press) coating, and (4) melt/dry coating. 

The resulting measurement of a compression force is highly correlated with a variety of tablet properties. As compression increases, so does tablet hardness and weight (at constant thickness and true density), along with a force required to eject a tablet. Many variables affect the force of compression press settings, press speed, punch length variation, punch wear, and damage, formulation and excipient properties. 

In the first set of experiments, the known effect of static pressure on cavitation was utilized. It is known that cavitation in fluids and porous media can be suppressed at high pressures. This effect is believed to occur due to the dissolution or collapse of the gaseous nuclei under the influence of pressure. Sonophoresis experiments were performed using skin compressed at 30 atm (between two smooth glass plates soaked in water placed in a compression press for two hours prior to sonophoresis experiments). They found that while application of ultrasound (IMHz, 2W/cm continuous) enhances estradiol permeability of the normal human epidermis by 13-fold, the corresponding enhancement for compressed skin is only about 1.75-fold. 

Tablet compression Press speed Tablet weight...

Foamed network structures (lofted structures) are also prepared in a compression press using Radlite technology. In this case, after applying full temperature and pressure for the requisite 2-A min, the platen gap is opened 1.5 times the original setting (for primarily open-cell structure) or 1.1-1.2 times the... 

The plant starts with twin-screw compounding of PP and glass fiber to produce a hot sheet, which is robotically transferred to a vertical compression press of 3300 tons. The fast-stroke press has automatic parallelism control. Another robot transfers parts to a 110-ton press that punches out attachment holes in the parts. Finally a third robot transfers parts to a machine that inserts hole reinforcements and inspects the parts. 

Figure 5.13 Book opening large compression press...

Matched steel dies are chrome plated and operated in heated compression presses. The entire premix is placed in the mold and pressed and heated 1 to 2 min to produce complete cure. Matched die molding is apphed to bulk molding compound, sheet molding compound, prepregs, and performs. 

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