Casting Machines In Dentistry

Casting Machines In Dentistry

The casting machine accelerates molten metal in the mold by centrifugal force under the air pressure of a vacuum or by a combination of both. All the casting machines work on the principle of centrifugal force which drives molten metal in the mold.

Dental Casting Machine Types

Types of Casting Machines

Centrifugal Casting Machine:

• This is carried out by melting alloy in a separate crucible and molten metal is forced in the mold by centrifugal force.
• Centrifugal force is created by spring-wound which depends on the amount of molten metal which is to be cast and desired speed of rotation.’
• Attach the crucible to the free arm of the casting machine. The spring of the casting machine is wound and locked.
• As the heating casting ring is placed and the alloy is melted to casting temperature, spring is released which leads to the initiation of rotational motion.
• The free arm of the crucible accelerates the initial rotational speed of the casting machine.

Use Of Casting Machines In Dental Laboratories

Electrical Resistance Heated Centrifugal Casting Machine:

• In this machine, the alloy is placed in a graphite or ceramic crucible and is heated with the help of a resistance-based heating unit.
• As crucible in this machine is located flush with the casting ring. This leads to the alloy button staying molten for a long time which ensures a continuous flow of molten metal and proper solidification.

Induction Casting Machine:

• Melt the alloy in an electric induction furnace inside the crucible which is surrounded by water-cooled metal tubing.
• As the alloy reaches casting temperature in air or vacuum, it is cast into the mold by centrifugal force.

Direct Current Arc Melting Machine:

• Alloy is vacuum melted and is cast by pressure in an argon atmosphere.
• The direct current arc is produced between the two electrodes, i.e. alloy and water-cooled tungsten electrodes.
• Since the temperature in the arc exceeds 4000°C, the alloy melts quickly which is the major disadvantage.

Dental Casting Equipment

Vacuum or Pressure-Assisted Casting Machine:

• Titanium and its alloys need a vacuum arc heating argon pressure casting machine.
• As the melting point of commercially pure titanium is 1671°C, so to prevent absorption of gases in a molten state, titanium should be cast in a protective atmosphere of argon or in a vacuum.
• Here a graphite or water-cooled copper crucible is used.
• Vacuum creates a negative pressure within the mold which helps to draw alloy in the mold.

Casting machines are also grouped based on the heating system, i.e.

1. Torch melted
2. Induction melted
3. Arc melted.

• Torch melting: In this fuel used is the combination of natural or artificial gas; oxygen and acetylene gas.

Function Of Casting Machines In Dental Prosthetics

• Induction melting: In this electrically conducting object is heated by electromagnetic induction. It is useful for melting high-fusing alloys, i.e. metal ceramic and base metal alloys.
• Arc melting: It melts industrial alloys such as steel. Direct current passes between two electrodes, i.e. a tungsten electrode and an alloy. It is used to melt high-fusion metals such as titanium.