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Other Advantages of Centrifugal Casting

The practice of Centrifugal casting, involves using a centrifugal force, the force when a body is subject to a high velocity spinning action to exert pressure onto molten metal as it is poured into a die, this method has a number of advantages over traditional static die-casting methods.

Other Advantages of Centrifugal Casting are: 

Reduction of Equipment Cost

• Centrifugal Casting offers a substantial saving on capital equipment when compared to forged products.

Reduction of Manufacturing Costs

• The uniformity resulting from the centrifugal casting process means that machining time and material waste are significantly reduced. Blowholes, sand residue, hard spots, cavities and porosity are virtually eliminated. 

Extensive Life

• Due to the finer grain and denser structure of parts with Centrifugal there is an increased usage life, greater endurance and impact without fracturing.

Fewer Castoffs

• The force used to distribute the molten metal as it is poured is so strong it displaces the lighter oxides and impurities to the centre of the hollow cylinder. It is then easy to remove these impurities. 

Flexibility

• The Centrifugal process allows economical production of a wide range of sizes, shapes and qualities.

In short centrifugal casting results in longer life, reduced rejects, reduction of manufacturing costs and production flexibility.

Turning Our Experience to Your Advantage

Gibson Centri Tech Ltd is recognised as one of the world’s Leading exponents of Centrifugal Casting Technology. With more that 30 years experience, the company has remained at the forefront of developments in the design and manufacture of Centrifugal Casting systems.

 Gibson’s services can include process and application selection, preparation of new plant and workshop layouts, project management, equipment installation, technical training and “know how” transfer.

The size of castings which Gibson’s machines manufacture range from 2cm up to several metres in diameter. The weight of the castings produced can be from a few grams to many tons. Products can range from miniature rings to 30 tonne rolls or sleeves for the steel industry. Most alloys can be cast using the centrifugal process, for instance Gibson Centri Tech provides equipment to cast bi metal double alloy steel rolls also a wide range of ferrous and non ferrous alloys. Centrifugal casting process is usually ideal for producing cylindrical castings but can also be utilised to cast other shapes.

Beginning with the careful evaluation of customers requirements, Gibson Centri Tech Limited will select the most efficient centrifugal casting equipment and process. Every stage of manufacture is under the company’s complete control and precise dimensional accuracy is assured. Prior to delivery, each machine is assembled and workshop tested to the most rigorous standards. Gibson Centri Tech’s extensive experience in Project management and commissioning ensures that every aspect of the scheme is coordinated to meet production deadlines and all the necessary performance criteria. 

Roll Making

The Gibson’s have been involved in roll making for nearly half a century; generations have had a major part in casting machine design and adapting the centrifugal casting process for leading roll makers. Since becoming an independent company, some thirty years ago, Gibson Centri Tech Limited have been involved with a number of roll making projects extending the technology around the world.

The Vertical or Horizontal Systems

Selection of the most suitable system to use is influenced by the type, size and quantity of rolls to be produced. Also to be considered are the initial investment costs, mould design and above all costs of the items to be produced.

The Vertical Process (Full Vertical)

The mould assembly is positioned vertically on a rotating table; long moulds are further supported with radial rollers. Metal pouring is carried out from the top with the shell layer poured first, followed by a core materials mould fill. The rotational speed is accurately controlled down to zero during the pouring process. One of the characteristics of the vertical method is the downward component of the gravity acting 90 Degrees to the centrifugal forces. This creates the shell layer with a taper or parabolic bore.

The process usually takes place below ground for safety reasons and to achieve a convenient pouring height.

The rigid system is commonly used for the production of solid mill rolls it involves a rotating turntable and radial mould support system, which is solid mill rolls it involves a rotating turntable and radial mould support system, which is rigidly fixed in the concrete foundations. The rigid system can also be used for the production of roll sleeves without the use of a radial upper support system, although that production can also be produced on a dedicated sleeve machine, depending on the customers specific requirements. 

Equipment Design (Vertical)

As the combined weight of the mould and liquid metal can be in excess of 100 tonnes, it is necessary that the deign be safe and robust. The loads exerted on parts of the equipment increase as the square of the rotational speed, so particular care has to be taken with mould bursting forces and eccentric lading as a result of mould tolerances and casting contraction.

The associated foundry equipment is subject to heavy handling and poor treatment, so design consideration has to be given to the whole working process . The timing and method of introducing shell and core metals require positive control. This timing control for present day installations is of the programmable computer variety, this assures the accuracy required.

Two methods of introducing the shell metal are used:

1. Directly into the bottom of the mould cavity allowing the metal to rise under centrifugal pressure.
2. Directly onto the roll barrel chill surface.

The Centri-Static Horizontal Process

The production of centrifugal castings produced in the Horizontal axis has been well established. Adapting the process for solid roll production initially came with many challenges.

The shell is produced in the horizontal axis on a roller or trunnion type-casting machine. On completion of casting the shell the mould containing the intermediate core metal layer and the flux , is rapidly stopped and transferred and locked onto the lower neck box (Drag). The upper neck box is located and the core material poured. The bonding process between the shell and core material is temperature critical, therefore close control is necessary. 

There are two systems of core metal introduction:

1. Via the top suing a Tundish type- pouring basin.
2. Via a bottom pour swirl gate using a pouring refractory tube through a prepared drag box. This system is more common and used for long length small diameter barrel rolls.

Equipment Design (Horizontal)

As mould/metal weights can be in excess of 50 tonnes, a robust safe installation, positively guarded, is used. This is designed to allow rapid access for mould removal.

Economic Considerations

To centrifugally cast the larger metalworking rolls, investment costs in the equipment and associated production tackle can be significant. Established roll makers who have invested in the equipment have seen a good return o the equipment, which has given services in excess of 20 years.

Smaller rolls can be produced with a lower investment. Hallow rolls are relatively easy to cast centrifugally; these Beam Mill Sleeves, Tube Mill Rolls, Roll Out Table Rollers, Mineral and Ore Grinding Rolls. Rolls for the food, rubber and feed industry can also be produced with relatively low investment.

With either the vertical or horizontal method of manufacture it is possible to make a wide range of rolls with various combinations of shell and core, e.g. high chrome, indefinite chill, SG, high chrome steel and HSS.

These can be with traditional analyses or with enhanced qualities to suit a wide range of rolling mill conditions and requirements. Gibson Centri-Tech  Limited also offers a complete service supplying the engineering components, the accessories and the technology required to produce the castings.

Horizontal and Vertical Process

It is acknowledged that both Horizontal and Vertical Centrifugal casting processes can be used with ferrous and non-ferrous material. The same machines can cast ferrous and non ferrous, the only difference is some process features have to be tailored to suit the alloy, such as:

• Spinning speeds
• Pouring rate
• Mould Temperatures
• Molten metal temperatures
• Mould Coating 
• Water Cooling

Horizontal Centrifugal Casting is best applied to castings of greater length than the diameter and which have cylindrical bore. This is why you will commonly find tubes between 300mm to 600mm long. It is possible to create shaped casting horizontally using a shaped mould or sand inserts.

Vertical Centrifugal Casting on the other hand is commonly used for Cylindrical shapes where the diameter exceeds the length or height of the casting one exception to this are steel mill rolls where using a roller guide system, casting with a longer length to the diameter are manufactured this is to allow the manufacture of solid castings.

It can also be used for complex casting shapes such as Ball Valves and Propeller.

Due to the gravitational pull while pouring the material a parabolic effect takes place in the bore, this can be altered by changing the speed for casting.

Gibson Centri Tech Limited – Leadership Through Innovation

Gibson Centri Tech Limited is acknowledged as one of the leading manufactures of technologically advanced Centrifugal Casting Machines.  

The services we provide include:

Process and Application

Preparation of new plant and workshop layouts

Projects installation technical and “know how transfer”

“We understand the unique environment of the foundry and we design and manufacture equipment accordingly”

Our Centrifugal Casting Machines are designed and manufactured in house using the latest CAD software and CNC equipment.

Beginning with the careful evaluation of customers requirements, we will select the most efficient Centrifugal Casting Equipment and process. Every stage of manufacture is under the company’s control and precise dimensional accuracy is assured. Prior to delivery, each machine is assembled and workshop tested to the most rigorous standards. Our extensive experience in project management and commissioning ensures that every aspect of the scheme is coordinated to meet production deadlines and all the necessary performance criteria.