Casting centrifugal

Centrifugal casting is used to produce parts with fine detail relatively free from included air. The mold is attached to a horizontal spinning disk which rotates at a speed of 5 to 30 m/s. The mold must be capable of having the polyurethane added from the center of the disk. The centrifugal forces move the denser polyurethane to the circumference of the mold and the air moves to the center. Some air vents may be required, as air can be trapped on horizontal surfaces. 

The material needs to be added at a steady rate to allow it to flow evenly to the outside of the spinning mold. When full, the mold and the material gelled may be removed and placed in an oven for the initial cure before demolding. 

It is important that the mold be dynamically balanced and securely locked in place on the spinning plate. The safety guards around the equipment must be capable of retaining the mold if it comes loose from the spinning plate. The polyurethane mixture must be carefully added to the center of the mold. If it hits the edge of the inlet, strands of fairy floss-like polyurethane may be formed. 

This technique is used to produce cylindrical products in cast iron, steel, and in alloys of aluminium, copper and nickel. T5q)ical parts made by this process are pipes, boilers, pressure vessels, flywheels, cylinder liners and other parts that are axis5mmetric. 

The main conversion techniques for UP resins are explained in Sections 16.7.6.1-16.7.6.10. 

Both hand lay-up and spray-up processes essentially involve placing reinforcement and liquid resin onto the surface of an open mold. As the two names suggest, hand lay-up involves applying the resin and reinforcement (for example, glass fiber chopped-strand mats) by hand, while spray-up uses spray equipment to deposit resin and reinforcement (for example, chopped glass fibers) onto the mold. These relatively cheap techmques are often used to produce large, complicated, strong composite parts such as boat hulls. 

Continuous lamination is another open-mold process. In this method resin is doctored onto a film of cellophane or poly(vinyl alcohol) and glass mat or chopped rovings placed on top of the resin. A second film is then placed on top of this, and the sandwich obtained is passed through rollers, which compact and remove air. They can also shape, as with corrugated type laminates. The sandwich is then passed through a heat source for curing. 

By suitable design, the structures obtained, having a glass content of up to 80%, can withstand very high pressures. 

The filament winding process may be combined with spray-up. This hybrid process is called chop hoop . The reinforcement of the resulting laminate than consists of a blend of continuous and randomly chopped fibers. 

Production rates of up to 50/h possible, but dependent on size. Lead time may be several weeks. 

Brake drums Pulley wheels Train wheels Flywheels Gun barrels Gear blanks Large bearing liners Engine-cylinder liners Pressure vessels Nozzles 

Shape complexity limited by nature of process, i.e. suited to parts with rotational symmetry. Contoured surfaces possible. 

Dual metal tubes that combine the properties of two metals in one application possible. Inserts and bosses possible, but undercuts are not. 

Placing of parting line important, i.e. avoid placement across critical dimensions. 

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Centrifugal atomizer Centrifugal casting Centrifugal cleaners Centrifugal compressors... 

Centrifugal casting is used to produce water softener tanks and pipe by saturating a reinforcement with thermosetting resin within a mold that is then rotated at high speed to consoHdate the laminate before curing. 

Centrifugal casting Process in which tubular products are fabricated through the application of resin and glass strand reinforcement to the inside of a mold that is rotated and heated. The process polymerizes the resin system. 

The Automatic processes are those such as pultrusion, filament winding, centrifugal casting and injection moulding. 

Fig. 7.53 Carbon concentration profiles of various centrifugally cast steels of differing silicon content, after 100 h at 1 093°C in a gas mixture with the following composition at the furnace inlet H2/34% CH4/30% HjO (after Kane" )...

Straight steel pipes up to 600 mm in diameter and six or more metres in length are usually lined by centrifugal casting. In this technique, the prepared preheated pipe is fitted with end caps and placed into the heated casting oven. Freshly mixed liquid polyurethane is then injected into the pipe which is then spun round its longitudinal axis until the polyurethane has cured to form a solid lining. 

Concrete Styrene-butadiene copolymer latex additions on centrifugally cast concrete [271]... 

R. G. Buchheit, T. E. Hinkebein, R F. Hlava, and D. G. Melton. The effects of latex additions on centrifugally cast concrete for internal pipeline protection. In Proceedings Volume, volume 4, pages 2854-2864.12th SPE/NACE Int Corrosion Congr (Houston, TX, 9/19-9/24), 1993. 

Liu J and Barnett SA. Thin yttrium-stabilized zirconia electrolyte solid oxide fuel cells by centrifugal casting. J Am Ceram Soc 2002 85 3096-3098. 

A 451 Centrifugally Cast Austenitic Steel Pipe for High-Temperature Service... 

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