Die casting is really a metal casting method that is described as forcing molten metal under high-pressure in a mold cavity. The mold cavity is created using two hardened tool steel dies which has been machined fit and work similarly to CNC precision machining during the process. Most die castings are produced from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin-based alloys. Dependant upon the type of metal being cast, a hot- or cold-chamber machine is utilized.
The casting equipment and the metal dies represent large capital costs which tends to limit the procedure to high-volume production. Production of parts using die casting is fairly simple, involving only four main steps, which ensures you keep the incremental cost per item low. It is actually especially best for a huge amount of small- to medium-sized castings, which is the reason die casting produces more castings than every other casting process. Die castings are characterized by a good surface finish (by casting standards) and dimensional consistency.
Two variants are pore-free die casting, which is used to eliminate gas porosity defects; and direct injection die casting, which is often used with zinc castings to minimize scrap and increase yield.
Die casting equipment was invented in 1838 when it comes to producing movable type for your printing industry. The first die casting-related patent was granted in 1849 for the small hand-operated machine with regards to mechanized printing type production. In 1885 Otto Mergenthaler invented the linotype machine, a computerized type-casting device which became the prominent sort of equipment in the publishing industry. The Soss die-casting machine, created in Brooklyn, NY, was the first machine to get bought from the open market in The United States. Other applications grew rapidly, with die casting facilitating the increase of consumer goods and appliances simply by making affordable the creation 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; water proof aluminum enclosure to, e.g. The Aluminum Association (AA) standards: AA 380, AA 384, AA 386, AA 390; and AZ91D magnesium.F This is a summary of the advantages 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 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 those of steel parts.
Silicon tombac: high-strength alloy manufactured 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 types of corrosion resistance. Such alloys are not utilized in foodservice applications for public health reasons. Type metal, an alloy of lead, tin and antimony (with sometimes traces of copper) can be used for casting hand-set type in 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 to 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 creating a parametric kind of a die casting:
Draft is the amount of slope or taper provided to cores or some other areas of the die cavity allowing for easy ejection in the casting in the die. All die cast surfaces that are parallel for the opening direction of the die require draft for that proper ejection of your casting from your die. Die castings that feature proper draft are simpler to remove in the die and bring about high-quality surfaces and a lot more precise finished product.
Fillet is the curved juncture of two surfaces that will have otherwise met at the sharp corner or edge. Simply, fillets could be put into a die casting to take out undesirable edges and corners.
Parting line represents the purpose where two different sides of a mold combine. The position of the parting line defines which side of your 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 should be mounted. For optimum integrity and strength in the die casting, bosses need to have universal wall thickness.
Ribs are included with a die casting to provide 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 these features will grip towards the die steel during solidification. To counteract this affect, generous draft needs to be included with hole and window features.
There are two basic types of die casting machines: hot-chamber machines and cold-chamber machines. These are generally rated by exactly how much clamping force they are able to 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, often known as gooseneck machines, depend on a pool of molten metal to feed the die. At the start of the cycle the piston from the machine is retracted, which allows the molten metal to fill the “gooseneck”. The pneumatic- or hydraulic-powered piston then forces this metal out of the Zinc die casting in to the die. Some great benefits of this system include fast cycle times (approximately 15 cycles one minute) and the convenience of melting the metal inside the casting machine. The disadvantages with this system are that it must be restricted to use with low-melting point metals and therefore aluminium cannot 21dexupky used mainly because it picks up several of the iron while in the molten pool. Therefore, hot-chamber machines are primarily combined with zinc-, tin-, and lead-based alloys.
They are used as soon as the casting alloy should not be found in hot-chamber machines; included in this are aluminium, zinc alloys with a large composition of aluminium, magnesium and copper. The process of these machines start out with melting the metal in a separate furnace. Then a precise quantity of molten metal is transported for the cold-chamber machine where it is actually fed into an unheated shot chamber (or injection cylinder). This shot will be driven to the die by a hydraulic or mechanical piston. The largest problem with this system will be the slower cycle time due to the must transfer the molten metal from your furnace to the cold-chamber machine.