Die casting is actually a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is generated using two hardened tool steel dies which were machined into condition and work similarly to aluminum die casting parts during the process. Most die castings are produced from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin-based alloys. Depending on the kind of metal being cast, a hot- or cold-chamber machine is commonly used.
The casting equipment along with the metal dies represent large capital costs and that will limit the method to high-volume production. Production of parts using die casting is pretty simple, involving only four main steps, which will keep the incremental cost per item low. It is especially suitable for a sizable number of small- to medium-sized castings, which is the reason die casting produces more castings than some other casting process. Die castings are observed as a good surface finish (by casting standards) and dimensional consistency.
Two variants are pore-free die casting, which is used to get rid of gas porosity defects; and direct injection die casting, that is utilized with zinc castings to minimize scrap and increase yield.
Die casting equipment was invented in 1838 with regards to producing movable type to the printing industry. The 1st die casting-related patent was granted in 1849 to get a small hand-operated machine just for mechanized printing type production. In 1885 Otto Mergenthaler invented the linotype machine, an automated type-casting device which became the prominent sort of equipment inside the publishing industry. The Soss die-casting machine, manufactured in Brooklyn, NY, was the very first machine to get bought from the open market in The United States. Other applications grew rapidly, with die casting facilitating the development of consumer goods and appliances if you make affordable the production of intricate parts in high volumes. In 1966, General Motors released the Acurad process.
The primary die casting alloys are: zinc, aluminium, magnesium, copper, lead, and tin; although uncommon, ferrous die casting is also possible. Specific die casting alloys include: Zamak; zinc aluminium; die casting parts to, e.g. The Aluminum Association (AA) standards: AA 380, AA 384, AA 386, AA 390; and AZ91D magnesium.F The following is a summary of some great benefits of each alloy:
Zinc: the easiest metal to cast; high ductility; high-impact strength; easily plated; economical for small parts; promotes long die life.
Aluminium: lightweight; high dimensional stability for complex shapes and thin walls; good corrosion resistance; good mechanical properties; high thermal and electrical conductivity; retains strength at high temperatures.
Magnesium: the simplest metal to machine; excellent strength-to-weight ratio; lightest alloy commonly die cast.
Copper: high hardness; high corrosion resistance; highest mechanical properties of alloys die cast; excellent wear resistance; excellent dimensional stability; strength approaching that from steel parts.
Silicon tombac: high-strength alloy created from copper, zinc and silicon. Often used as a substitute for investment casted steel parts.
Lead and tin: high density; extremely close dimensional accuracy; used for special kinds of corrosion resistance. Such alloys are not found in foodservice applications for public health reasons. Type metal, an alloy of lead, tin and antimony (with sometimes traces of copper) is utilized for casting hand-set enter letterpress printing and hot foil blocking. Traditionally cast in hand jerk moulds now predominantly die cast after the industrialisation from the type foundries. Around 1900 the slug casting machines came onto the market and added further automation, with sometimes dozens of casting machines at one newspaper office.
There are a number of geometric features to be considered when designing a parametric style of a die casting:
Draft is the quantity of slope or taper presented to cores or other parts of the die cavity to enable for quick ejection from the casting in the die. All die cast surfaces that happen to be parallel to the opening direction of your die require draft to the proper ejection in the casting through the die. Die castings that come with proper draft are easier to remove in the die and lead to high-quality surfaces and more precise finished product.
Fillet will be the curved juncture of two surfaces that could have otherwise met at a sharp corner or edge. Simply, fillets may be included in a die casting to get rid of undesirable edges and corners.
Parting line represents the idea in which two different sides of any mold get together. The location of the parting line defines which side of the die will be the cover and the ejector.
Bosses are added to die castings to offer as stand-offs and mounting points for parts that will have to be mounted. For optimum integrity and strength of the die casting, bosses must have universal wall thickness.
Ribs are put into a die casting to offer added support for designs which need maximum strength without increased wall thickness.
Holes and windows require special consideration when die casting since the perimeters of the features will grip for the die steel during solidification. To counteract this affect, generous draft should be included with hole and window features.
There are 2 basic kinds of die casting machines: hot-chamber machines and cold-chamber machines. These are rated by how much clamping force they can apply. Typical ratings are between 400 and 4,000 st (2,500 and 25,400 kg).
Hot-chamber die casting
Schematic of a hot-chamber machine
Hot-chamber die casting, often known as gooseneck machines, depend on a swimming pool of molten metal to give the die. At the start of the cycle the piston of the machine is retracted, which allows the molten metal to fill the “gooseneck”. The pneumatic- or hydraulic-powered piston then forces this metal out from the die casting parts in to the die. Some great benefits of this technique include fast cycle times (approximately 15 cycles a minute) and also the comfort of melting the metal in the casting machine. The disadvantages with this system are that it must be restricted to use with low-melting point metals and that aluminium cannot 21dexupky used since it picks up several of the iron in the molten pool. Therefore, hot-chamber machines are primarily used with zinc-, tin-, and lead-based alloys.
These are typically used if the casting alloy should not be utilized in hot-chamber machines; some examples are aluminium, zinc alloys using a large composition of aluminium, magnesium and copper. The procedure for these machines get started with melting the metal in a separate furnace. A precise quantity of molten metal is transported for the cold-chamber machine where it can be fed into an unheated shot chamber (or injection cylinder). This shot will be driven in to the die with a hydraulic or mechanical piston. The greatest downside of this method is the slower cycle time due to the must transfer the molten metal in the furnace on the cold-chamber machine.