Die casting is actually a metal casting method that is described as forcing molten metal under high-pressure into a mold cavity. The mold cavity is produced using two hardened tool steel dies which has been machined fit and work similarly to aluminum die casting parts during the process. Most die castings are made of non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin-based alloys. Based on the sort of metal being cast, a hot- or cold-chamber machine can be used.
The casting equipment as well as the metal dies represent large capital costs and that is likely to limit the method to high-volume production. Manufacture of parts using die casting is fairly simple, involving only four main steps, which ensures you keep the incremental cost per item low. It can be especially suited for a large amount of small- to medium-sized castings, which is why die casting produces more castings than any other casting process. Die castings are seen as a a really 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, which is used with zinc castings to minimize scrap and increase yield.
Die casting equipment was invented in 1838 with regards to producing movable type for that printing industry. The first die casting-related patent was granted in 1849 to get a small hand-operated machine when it comes to mechanized printing type production. In 1885 Otto Mergenthaler invented the linotype machine, an automated type-casting device which took over as the prominent sort of equipment from the publishing industry. The Soss die-casting machine, produced in Brooklyn, NY, was the 1st machine to become purchased in the open market in America. Other applications grew rapidly, with die casting facilitating the growth of consumer goods and appliances through making affordable the production of intricate parts in high volumes. In 1966, General Motors released the Acurad process.
The key die casting alloys are: zinc, aluminium, magnesium, copper, lead, and tin; although uncommon, ferrous die casting can also be possible. Specific die casting alloys include: Zamak; zinc aluminium; aluminum die casting to, e.g. The Aluminum Association (AA) standards: AA 380, AA 384, AA 386, AA 390; and AZ91D magnesium.F This is an overview of the main advantages 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 best 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 made from copper, zinc and silicon. Often used as a replacement for investment casted steel parts.
Lead and tin: high density; extremely close dimensional accuracy; utilized for special kinds of corrosion resistance. Such alloys usually 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 used for casting hand-set type letterpress printing and hot foil blocking. Traditionally cast in hand jerk moulds now predominantly die cast after the industrialisation of your 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 numerous of geometric features to be considered when creating a parametric kind of a die casting:
Draft is the amount of slope or taper given to cores or other elements of the die cavity to permit for convenient ejection of the casting from the die. All die cast surfaces which are parallel for the opening direction from the die require draft for your proper ejection from the casting from your die. Die castings that come with proper draft are easier to remove through the die and bring about high-quality surfaces and a lot more precise finished product.
Fillet is the curved juncture of two surfaces that might have otherwise met in a sharp corner or edge. Simply, fillets could be included with a die casting to remove undesirable edges and corners.
Parting line represents the point at which two different sides of any mold combine. The location of the parting line defines which side in the die will be the cover and which is the ejector.
Bosses are included in die castings to serve as stand-offs and mounting points for parts that must be mounted. For maximum integrity and strength from the die casting, bosses need to have universal wall thickness.
Ribs are included in a die casting to deliver added support for designs that need maximum strength without increased wall thickness.
Holes and windows require special consideration when die casting for the reason that perimeters of those features will grip for the die steel during solidification. To counteract this affect, generous draft must be put into hole and window features.
There are two basic kinds of die casting machines: hot-chamber machines and cold-chamber machines. These are rated by just 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 the hot-chamber machine
Hot-chamber die casting, also called gooseneck machines, rely upon a pool of molten metal to give the die. At the beginning of the cycle the piston of the machine is retracted, that enables the molten metal to fill the “gooseneck”. The pneumatic- or hydraulic-powered piston then forces this metal out from the die casting parts to the die. The benefits of this system include fast cycle times (approximately 15 cycles a minute) and also the comfort of melting the metal inside the casting machine. The disadvantages on this system are that it must be limited to use with low-melting point metals and therefore aluminium cannot 21dexupky used mainly because it picks up some of the iron while in the molten pool. Therefore, hot-chamber machines are primarily combined with zinc-, tin-, and lead-based alloys.
These are typically used if the casting alloy should not be utilized in hot-chamber machines; such as aluminium, zinc alloys by using a large composition of aluminium, magnesium and copper. This process of these machines begin with melting the metal within a separate furnace. Then the precise quantity of molten metal is transported on the cold-chamber machine where it really is fed into an unheated shot chamber (or injection cylinder). This shot is going to be driven to the die by a hydraulic or mechanical piston. The biggest downside of this technique will be the slower cycle time due to the should transfer the molten metal through the furnace on the cold-chamber machine.