13
DIE CASTING

Die casting

Embed Size (px)

Citation preview

Page 1: Die casting

DIE CASTING

Page 2: Die casting

What is Die Casting

It is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process.

Page 3: Die casting

Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminums, magnesium, lead, pewter and tin based alloys. Depending on the type of metal being cast, a hot- or cold-chamber machine is used.

Page 4: Die casting

Equipment for Die Casting

Hot-chamber die casting

- also known as gooseneck machines, rely upon a pool of molten metal to feed the die. The pneumatic or hydraulic powered piston then forces this metal out of the gooseneck into the die.

Page 5: Die casting

The advantages of this system include fast cycle times (approximately 15 cycles a minute) and the convenience of melting the metal in the casting machine. The disadvantages of this system are that it is limited to use with low-melting point metals and that aluminium cannot be used because it picks up some of the iron while in the molten pool.

Page 6: Die casting

Cold-chamber die casting- These are used when the casting

alloy cannot be used in hot-chamber machines; these include aluminium, zinc alloys with a large composition of aluminium, magnesium and copper. The process for these machines start with melting the metal in a separate furnace.

Page 7: Die casting

These are used when the casting alloy cannot be used in hot-chamber machines; these include aluminums, zinc alloys with a large composition of aluminums, magnesium and copper. The process for these machines start with melting the metal in a separate furnace.

Page 8: Die casting

Die Casting Processes

Die Preparationa. Wafer mounting- a step that is

performed during the die preparation of a wafer as part of the process of semiconductor fabrication. During this step, the wafer is mounted on a plastic tape that is attached to a ring.

Page 9: Die casting

Die Filling – Molten metal is injected into a

closed mold at high pressures. The pressure in the mold is maintained until the casting has reached the required level of solidification.Ejection

– Shots are forced out by ejector pins.Shakeout

– Shots are separated into the different components and scrap is removed. Components are generally inspected at shakeout for defects.

Page 10: Die casting

Die Casting DefectsIn die casting the most common defects

are misruns and cold shuts. These defects can be caused by cold dies, low metal temperature, dirty metal, lack of venting, or too much lubricant. Other possible defects are gas porosity, shrinkage porosity, hot tears, and flow marks. Flow marks are marks left on the surface of the casting due to poor gating, sharp corners, or excessive lubricant.

Page 11: Die casting

Shrinkage defects- Shrinkage defects can occur when

standard feed metal is not available to compensate for shrinkage as the thick metal solidifies.

A. Open shrinkage defects are open to the atmosphere, therefore as the shrinkage cavity forms air compensates.

B. Closed shrinkage defects, also known as shrinkage porosity, are defects that form within the casting. Isolated pools of liquid form inside solidified metal, which are called hot spots.

Page 12: Die casting

Gas porosity-Gas porosity is the formation of bubbles

within the casting after it has cooled.Misruns and cold shuts

- closely related and both involve the material freezing before it completely fills the mold cavity. These types of defects are serious because the area surrounding the defect is significantly weaker than intended. The castability and viscosity of the material can be important factors with these problems.

Page 13: Die casting

Die Casted Products