Die casting is a metal casting method that is characterized by forcing molten metal under high-pressure in to a mold cavity. The mold cavity is created using two hardened tool steel dies which has been machined into condition 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. Depending on the sort of metal being cast, a hot- or cold-chamber machine is commonly used.
The casting equipment and also the metal dies represent large capital costs and also this has a tendency to limit the process to high-volume production. Creation of parts using die casting is pretty simple, involving only four main steps, which will keep the incremental cost per item low. It is actually especially best for a big amount of small- to medium-sized castings, which explains 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, that is utilized to remove 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 just for producing movable type to 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 took over as the prominent type of equipment in the publishing industry. The Soss die-casting machine, manufactured in Brooklyn, NY, was the 1st machine being purchased in the open market in Canada And America. Other applications grew rapidly, with die casting facilitating the development of consumer goods and appliances through making 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 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 most convenient 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 relating to steel parts.
Silicon tombac: high-strength alloy manufactured from copper, zinc and silicon. Often used as an alternative for investment casted steel parts.
Lead and tin: high density; extremely close dimensional accuracy; utilized for special types of corrosion resistance. Such alloys will not be employed 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 lots of casting machines at one newspaper office.
There are many of geometric features to be considered when designing a parametric kind of a die casting:
Draft is the level of slope or taper made available to cores or other elements of the die cavity allowing for easy ejection of your casting from your die. All die cast surfaces that happen to be parallel for the opening direction from the die require draft to the proper ejection of the casting in the die. Die castings which feature proper draft are simpler to remove from the die and result in high-quality surfaces and a lot more precise finished product.
Fillet is the curved juncture of two surfaces that will have otherwise met at a sharp corner or edge. Simply, fillets could be put into a die casting to remove undesirable edges and corners.
Parting line represents the idea from which two different sides of your mold come together. The location of the parting line defines which side of your die may be the cover and which is the ejector.
Bosses are included with die castings to provide as stand-offs and mounting points for parts that will need to be mounted. For maximum integrity and strength of the die casting, bosses will need to have universal wall thickness.
Ribs are added to a die casting to supply added support for designs which need maximum strength without increased wall thickness.
Holes and windows require special consideration when die casting because the perimeters of the features will grip on the die steel during solidification. To counteract this affect, generous draft needs 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 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 called gooseneck machines, rely upon a pool of molten metal to feed the die. At the beginning of the cycle the piston of the machine is retracted, that allows the molten metal to fill the “gooseneck”. The pneumatic- or hydraulic-powered piston then forces this metal from the CNC precision machining in the die. The benefits of this method include fast cycle times (approximately 15 cycles one minute) and also the comfort of melting the metal in the casting machine. The disadvantages on this system are that it is restricted to use with low-melting point metals and this aluminium cannot 21dexupky used because it picks up a few of the iron whilst in the molten pool. Therefore, hot-chamber machines are primarily used with zinc-, tin-, and lead-based alloys.
These are typically used when the casting alloy cannot be found in hot-chamber machines; included in this are aluminium, zinc alloys having a large composition of aluminium, magnesium and copper. This process for such machines start with melting the metal in the separate furnace. Then this precise quantity of molten metal is transported to the cold-chamber machine where it can be fed into an unheated shot chamber (or injection cylinder). This shot is going to be driven to the die from a hydraulic or mechanical piston. The greatest disadvantage of this product is the slower cycle time due to should transfer the molten metal in the furnace to the cold-chamber machine.