Die casting is actually a metal casting procedure that is seen as a forcing molten metal under high-pressure right into a mold cavity. The mold cavity is made using two hardened tool steel dies which has been machined into condition and work similarly to CNC precision machining along the way. Most die castings are made of non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin-based alloys. Depending on the form of metal being cast, a hot- or cold-chamber machine is utilized.
The casting equipment along with the metal dies represent large capital costs and that will limit the method to high-volume production. Creation of parts using die casting is relatively simple, involving only four main steps, which ensures you keep the incremental cost per item low. It is especially suited for a huge amount of small- to medium-sized castings, which explains why die casting produces more castings than some other casting process. Die castings are seen as a a very good surface finish (by casting standards) and dimensional consistency.
Two variants are pore-free die casting, that is utilized to eliminate gas porosity defects; and direct injection die casting, which is used with zinc castings to reduce scrap and increase yield.
Die casting equipment was invented in 1838 just for producing movable type for that printing industry. The initial die casting-related patent was granted in 1849 for the small hand-operated machine for the purpose of mechanized printing type production. In 1885 Otto Mergenthaler invented the linotype machine, a computerized type-casting device which had become the prominent sort of equipment in the publishing industry. The Soss die-casting machine, made in Brooklyn, NY, was the very first machine to get purchased in the open market in The United States. Other applications grew rapidly, with die casting facilitating the development 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 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; 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 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 an alternative for investment casted steel parts.
Lead and tin: high density; extremely close dimensional accuracy; used for special types 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 commonly used for casting hand-set type letterpress printing and hot foil blocking. Traditionally cast at 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 many casting machines at one newspaper office.
There are a variety of geometric features that need considering when creating a parametric model of a die casting:
Draft is the volume of slope or taper presented to cores or some other aspects of the die cavity to allow for quick ejection from the casting in the die. All die cast surfaces that are parallel towards the opening direction of the die require draft for your proper ejection of the casting from the die. Die castings that come with proper draft are easier to remove from the die and result in high-quality surfaces and much more precise finished product.
Fillet will be the curved juncture of two surfaces that would have otherwise met at a sharp corner or edge. Simply, fillets can be added to a die casting to get rid of undesirable edges and corners.
Parting line represents the point at which two different sides of your mold combine. The location of the parting line defines which side of your die will be the cover and the ejector.
Bosses are included in die castings to provide as stand-offs and mounting points for parts that will need to be mounted. For max integrity and strength of your die casting, bosses need to have universal wall thickness.
Ribs are added to a die casting to offer added support for designs that require maximum strength without increased wall thickness.
Holes and windows require special consideration when die casting since the perimeters of such features will grip to the die steel during solidification. To counteract this affect, generous draft ought to be included in hole and window features.
There are two basic varieties of die casting machines: hot-chamber machines and cold-chamber machines. These are rated by simply how much clamping force they may 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 pool of molten metal to give the die. At the beginning of the cycle the piston from the machine is retracted, allowing the molten metal to fill the “gooseneck”. The pneumatic- or hydraulic-powered piston then forces this metal from the Zinc die casting into the die. The benefits of this system include fast cycle times (approximately 15 cycles one minute) along with the convenience of melting the metal inside the casting machine. The disadvantages on this system are that it is confined to use with low-melting point metals and that aluminium cannot 21dexupky used since it picks up some of the iron whilst in the molten pool. Therefore, hot-chamber machines are primarily combined with zinc-, tin-, and lead-based alloys.
These are generally used once the casting alloy can not be used in hot-chamber machines; included in this are aluminium, zinc alloys having a large composition of aluminium, magnesium and copper. The method for these particular machines begin with melting the metal in the separate furnace. Then a precise amount 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 then driven into the die by way of a hydraulic or mechanical piston. The greatest drawback to this technique is definitely the slower cycle time as a result of need to transfer the molten metal from the furnace on the cold-chamber machine.