Die casting can be a metal casting procedure that is described as forcing molten metal under high pressure in to a mold cavity. The mold cavity is generated using two hardened tool steel dies that have been machined fit and work similarly to aluminum die casting parts during the process. Most die castings are manufactured from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin-based alloys. Dependant upon the sort of metal being cast, a hot- or cold-chamber machine is 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. Creation of parts using die casting is relatively simple, involving only four main steps, which keeps the incremental cost per item low. It is actually especially suited for a large volume of small- to medium-sized castings, which explains why die casting produces more castings than every other casting process. Die castings are observed as a very good surface finish (by casting standards) and dimensional consistency.
Two variants are pore-free die casting, which is often 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 just for producing movable type for the printing industry. The initial die casting-related patent was granted in 1849 for any 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 had become the prominent type of equipment in the publishing industry. The Soss die-casting machine, manufactured in Brooklyn, NY, was the first machine to be purchased in the open market in America. Other applications grew rapidly, with die casting facilitating the increase of consumer goods and appliances simply by making affordable the production of intricate parts in high volumes. In 1966, General Motors released the Acurad process.
The principle 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; die casting parts 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 benefits of each alloy:
Zinc: the simplest 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 most convenient 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 of steel parts.
Silicon tombac: high-strength alloy made from copper, zinc and silicon. Often used as a substitute for investment casted steel parts.
Lead and tin: high density; extremely close dimensional accuracy; utilized for special forms of corrosion resistance. Such alloys are not used 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 enter letterpress printing and hot foil blocking. Traditionally cast at hand jerk moulds now predominantly die cast once 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 many of geometric features to be considered when creating a parametric model of a die casting:
Draft is the level of slope or taper made available to cores or another areas of the die cavity allowing for convenient ejection of your casting through the die. All die cast surfaces which can be parallel towards the opening direction of your die require draft for that proper ejection of the casting from the die. Die castings that feature proper draft are simpler to remove from your die and result in high-quality surfaces plus more precise finished product.
Fillet will be the curved juncture of two surfaces that would have otherwise met with a sharp corner or edge. Simply, fillets can be added to a die casting to eliminate undesirable edges and corners.
Parting line represents the purpose where two different sides of any mold combine. The position of the parting line defines which side in the die may 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 will have to be mounted. For maximum integrity and strength of the die casting, bosses need to have universal wall thickness.
Ribs are included with 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 as the perimeters of such features will grip on the die steel during solidification. To counteract this affect, generous draft needs to be added to hole and window features.
There are 2 basic forms 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 your hot-chamber machine
Hot-chamber die casting, also known as gooseneck machines, rely upon a pool of molten metal to give the die. At the start 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 of your die casting parts in the die. The benefits of this technique 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 confined to use with low-melting point metals and that aluminium cannot 21dexupky used since it picks up some of the iron in the molten pool. Therefore, hot-chamber machines are primarily combined with zinc-, tin-, and lead-based alloys.
These are typically used as soon as the casting alloy can not be found in hot-chamber machines; these include aluminium, zinc alloys by using a large composition of aluminium, magnesium and copper. This process of these machines start with melting the metal in the separate furnace. Then a precise volume of molten metal is transported towards the cold-chamber machine where it really is fed into an unheated shot chamber (or injection cylinder). This shot will then be driven in to the die by a hydraulic or mechanical piston. The largest downside of this technique is definitely the slower cycle time because of the need to transfer the molten metal from the furnace on the cold-chamber machine.