Die casting is a metal casting procedure that is characterized by 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 CNC precision machining along the way. Most die castings are produced from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin-based alloys. Dependant upon the form of metal being cast, a hot- or cold-chamber machine is commonly used.
The casting equipment as well as the metal dies represent large capital costs which will limit the method to high-volume production. Manufacture of parts using die casting is relatively simple, involving only four main steps, which keeps the incremental cost per item low. It is especially designed for a big volume of small- to medium-sized castings, which explains why die casting produces more castings than almost every other casting process. Die castings are characterized by a very good surface finish (by casting standards) and dimensional consistency.
Two variants are pore-free die casting, which is often used to eliminate gas porosity defects; and direct injection die casting, which is used with zinc castings to lower scrap and increase yield.
Die casting equipment was invented in 1838 with regards to producing movable type for your 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, a computerized type-casting device which took over as the prominent type of equipment in the publishing industry. The Soss die-casting machine, created in Brooklyn, NY, was the initial machine to be sold in the open market in America. Other applications grew rapidly, with die casting facilitating the growth of consumer goods and appliances if you make affordable producing intricate parts in high volumes. In 1966, General Motors released the Acurad process.
The main die casting alloys are: zinc, aluminium, magnesium, copper, lead, and tin; although uncommon, ferrous die casting is likewise 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 best 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 easiest 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 of copper, zinc and silicon. Often used as a replacement for investment casted steel parts.
Lead and tin: high density; extremely close dimensional accuracy; useful for special types of corrosion resistance. Such alloys will not be 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 letterpress printing and hot foil blocking. Traditionally cast at your fingertips jerk moulds now predominantly die cast after the industrialisation from the type foundries. Around 1900 the slug casting machines came into the market and added further automation, with sometimes lots of casting machines at one newspaper office.
There are numerous of geometric features to be considered when producing a parametric kind of a die casting:
Draft is the quantity of slope or taper made available to cores or another areas of the die cavity to enable for easy ejection of the casting through the die. All die cast surfaces which can be parallel towards the opening direction of the die require draft to the proper ejection from the casting from the die. Die castings that feature proper draft are easier to remove in the die and lead to high-quality surfaces and more precise finished product.
Fillet is the curved juncture of two surfaces that would have otherwise met at the sharp corner or edge. Simply, fillets can be put into a die casting to get rid of undesirable edges and corners.
Parting line represents the idea in which two different sides of a mold come together. The position of the parting line defines which side of your die will be the cover and which is the ejector.
Bosses are included with die castings to offer 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 included in 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 added to hole and window features.
The two main basic forms of die casting machines: hot-chamber machines and cold-chamber machines. They are rated by 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, also known as gooseneck machines, rely upon a swimming pool of molten metal to give the die. At the beginning of the cycle the piston of your 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 the die. The main advantages of this system include fast cycle times (approximately 15 cycles one minute) and also the convenience of melting the metal inside the casting machine. The disadvantages with 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 a number of the iron whilst in the molten pool. Therefore, hot-chamber machines are primarily used in combination with zinc-, tin-, and lead-based alloys.
These are typically used if the casting alloy can not be employed in hot-chamber machines; some examples are aluminium, zinc alloys with a large composition of aluminium, magnesium and copper. This process for these machines start with melting the metal in a separate furnace. Then this precise amount of molten metal is transported to the cold-chamber machine where it is actually fed into an unheated shot chamber (or injection cylinder). This shot is then driven in the die with a hydraulic or mechanical piston. The most significant problem with this system will be the slower cycle time due to must transfer the molten metal from the furnace for the cold-chamber machine.