An engine block with aluminum and magnesium die castings

Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter, and tin-based alloys. Depending on the type of metal being cast, a hot- or cold-chamber machine is used.

The casting equipment and the metal dies represent large capital costs and this tends to limit the process 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 suited for a large quantity of small- to medium-sized castings, which is why die casting produces more castings than any other casting process.[1] Die castings are characterized by a very good surface finish (by casting standards) and dimensional consistency.


Die casting equipment was invented in 1838 for the purpose of producing movable type for the printing industry. The first die casting-related patent was granted in 1849 for a small hand-operated machine for the purpose of mechanized printing type production. In 1885 Ottmar Mergenthaler invented the Linotype machine, which cast an entire line of type as a single unit, using a die casting process. It nearly completely replaced setting type by hand in the publishing industry. The Soss die-casting machine, manufactured in Brooklyn, NY, was the first machine to be sold in the open market in North America.[2] Other applications grew rapidly, with die casting facilitating the growth of consumer goods, and appliances, by greatly reducing the production cost of intricate parts in high volumes.[3] In 1966,[4] General Motors released the Acurad process.[5]

Cast metal

The main die casting alloys are: zinc, aluminium, magnesium, copper, lead, and tin; although uncommon, ferrous die casting is also possible.[6] Specific die casting alloys include: zinc aluminium; aluminium to, e.g. The Aluminum Association (AA) standards: AA 380, AA 384, AA 386, AA 390; and AZ91D magnesium.[7] The following is a summary of the advantages of each alloy:[8]

As of 2008, maximum weight limits for aluminium, brass, magnesium, and zinc castings are estimated at approximately 70 pounds (32 kg), 10 lb (4.5 kg), 44 lb (20 kg), and 75 lb (34 kg), respectively.[9] By late-2019, press machines capable of die casting single pieces over-100 kilograms (220 lb) were being used to produce aluminium chassis components for cars.[10]

The material used defines the minimum section thickness and minimum draft required for a casting as outlined in the table below. The thickest section should be less than 13 mm (0.5 in), but can be greater.[11]

Metal Minimum section Minimum draft
Aluminium alloys 0.89 mm (0.035 in) 1:100 (0.6°)
Brass and bronze 1.27 mm (0.050 in) 1:80 (0.7°)
Magnesium alloys 1.27 mm (0.050 in) 1:100 (0.6°)
Zinc alloys 0.63 mm (0.025 in) 1:200 (0.3°)

Design geometry

This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed. (December 2017) (Learn how and when to remove this message)

There are a number of geometric features to be considered when creating a parametric model of a die casting:


There are two basic types of die casting machines: hot-chamber machines and cold-chamber machines.[14] 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).[8]

Hot-chamber die casting

Schematic of a hot-chamber machine

Hot-chamber die casting, also known as 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, which allows the molten metal to fill the "gooseneck". The pneumatic- or hydraulic-powered piston then forces this metal out of the gooseneck into the die. The advantages of this system include fast cycle times (approximately 15 cycles a minute) and the convenience of melting the metal in the casting machine. The disadvantages of this system are that it is limited to use with low-melting point metals and that aluminium cannot be used because it picks up some of the iron while in the molten pool. Therefore, hot-chamber machines are primarily used with zinc-, tin-, and lead-based alloys.[14]

Cold-chamber die casting

Schematic of a cold-chamber die casting machine

These are used when the casting alloy cannot be used in hot-chamber machines; these include aluminium, zinc alloys with a large composition of aluminium, magnesium and copper. The process for these machines start with melting the metal in a separate furnace.[15] Then a precise amount of molten metal is transported to the cold-chamber machine where it is fed into an unheated shot chamber (or injection cylinder). This shot is then driven into the die by a hydraulic or mechanical piston. The biggest disadvantage of this system is the slower cycle time due to the need to transfer the molten metal from the furnace to the cold-chamber machine.[16]

Mold or tooling

The ejector die half
The cover die half

Two dies are used in die casting; one is called the "cover die half" and the other the "ejector die half". Where they meet is called the parting line. The cover die contains the sprue (for hot-chamber machines) or shot hole (for cold-chamber machines), which allows the molten metal to flow into the dies; this feature matches up with the injector nozzle on the hot-chamber machines or the shot chamber in the cold-chamber machines. The ejector die contains the ejector pins and usually the runner, which is the path from the sprue or shot hole to the mould cavity. The cover die is secured to the stationary, or front, platen of the casting machine, while the ejector die is attached to the movable platen. The mould cavity is cut into two cavity inserts, which are separate pieces that can be replaced relatively easily and bolt into the die halves.[17]

The dies are designed so that the finished casting will slide off the cover half of the die and stay in the ejector half as the dies are opened. This assures that the casting will be ejected every cycle because the ejector half contains the ejector pins to push the casting out of that die half. The ejector pins are driven by an ejector pin plate, which accurately drives all of the pins at the same time and with the same force, so that the casting is not damaged. The ejector pin plate also retracts the pins after ejecting the casting to prepare for the next shot. There must be enough ejector pins to keep the overall force on each pin low, because the casting is still hot and can be damaged by excessive force. The pins still leave a mark, so they must be located in places where these marks will not hamper the casting's purpose.[17]

Other die components include cores and slides. Cores are components that usually produce holes or opening, but they can be used to create other details as well. There are three types of cores: fixed, movable, and loose. Fixed cores are ones that are oriented parallel to the pull direction of the dies (i.e. the direction the dies open), therefore they are fixed, or permanently attached to the die. Movable cores are ones that are oriented in any other way than parallel to the pull direction. These cores must be removed from the die cavity after the shot solidifies, but before the dies open, using a separate mechanism. Slides are similar to movable cores, except they are used to form undercut surfaces. The use of movable cores and slides greatly increases the cost of the dies.[17] Loose cores, also called pick-outs, are used to cast intricate features, such as threaded holes. These loose cores are inserted into the die by hand before each cycle and then ejected with the part at the end of the cycle. The core then must be removed by hand. Loose cores are the most expensive type of core, because of the extra labor and increased cycle time.[11] Other features in the dies include water-cooling passages and vents along the parting lines. These vents are usually wide and thin (approximately 0.13 mm or 0.005 in) so that when the molten metal starts filling them the metal quickly solidifies and minimizes scrap. No risers are used because the high pressure ensures a continuous feed of metal from the gate.[18]

The most important material properties for the dies are thermal shock resistance and softening at elevated temperature; other important properties include hardenability, machinability, heat checking resistance, weldability, availability (especially for larger dies), and cost. The longevity of a die is directly dependent on the temperature of the molten metal and the cycle time.[17] The dies used in die casting are usually made out of hardened tool steels, because cast iron cannot withstand the high pressures involved, therefore the dies are very expensive, resulting in high start-up costs.[18] Metals that are cast at higher temperatures require dies made from higher alloy steels.[19]

Die and component material and hardness for various cast metals
Die component Cast metal
Tin, lead & zinc Aluminium & magnesium Copper & brass
Material Hardness Material Hardness Material Hardness
Cavity inserts P20[note 1] 290–330 HB H13 42–48 HRC DIN 1.2367 38–44 HRC
H11 46–50 HRC H11 42–48 HRC H20, H21, H22 44–48 HRC
H13 46–50 HRC
Cores H13 46–52 HRC H13 44–48 HRC DIN 1.2367 40–46 HRC
DIN 1.2367 42–48 HRC
Core pins H13 48–52 HRC DIN 1.2367 prehard 37–40 HRC DIN 1.2367 prehard 37–40 HRC
Sprue parts H13 48–52 HRC H13
DIN 1.2367
46–48 HRC
44–46 HRC
DIN 1.2367 42–46 HRC
Nozzle 420 40–44 HRC H13 42–48 HRC DIN 1.2367
40–44 HRC
42–48 HRC
Ejector pins H13[note 2] 46–50 HRC H13[note 2] 46–50 HRC H13[note 2] 46–50 HRC
Plunger shot sleeve H13[note 2] 46–50 HRC H13[note 2]
DIN 1.2367[note 2]
42–48 HRC
42–48 HRC
DIN 1.2367[note 2]
H13[note 2]
42–46 HRC
42–46 HRC
Holder block 4140 prehard ~300 HB 4140 prehard ~300 HB 4140 prehard ~300 HB

The main failure mode for die casting dies is wear or erosion. Other failure modes are heat checking and thermal fatigue. Heat checking is when surface cracks occur on the die due to a large temperature change on every cycle. Thermal fatigue is when surface cracks occur on the die due to a large number of cycles.[20]

Typical die temperatures and life for various cast materials[21]
Zinc Aluminium Magnesium Brass (leaded yellow)
Maximum die life [number of cycles] 1,000,000 100,000 100,000 10,000
Die temperature [°C (°F)] 218 (425) 288 (550) 260 (500) 500 (950)
Casting temperature [°C (°F)] 400 (760) 660 (1220) 760 (1400) 1090 (2000)


The following are the four steps in traditional die casting, also known as high-pressure die casting,[5] these are also the basis for any of the die casting variations: die preparation, filling, ejection, and shakeout. The dies are prepared by spraying the mould cavity with lubricant. The lubricant both helps control the temperature of the die and it also assists in the removal of the casting. The dies are then closed and molten metal is injected into the dies under high pressure; between 10 and 175 megapascals (1,500 and 25,400 psi). Once the mould cavity is filled, the pressure is maintained until the casting solidifies. The dies are then opened and the shot (shots are different from castings because there can be multiple cavities in a die, yielding multiple castings per shot) is ejected by the ejector pins. Finally, the shakeout involves separating the scrap, which includes the gate, runners, sprues and flash, from the shot. This is often done using a special trim die in a power press or hydraulic press. Other methods of shaking out include sawing and grinding. A less labor-intensive method is to tumble shots if gates are thin and easily broken; separation of gates from finished parts must follow. This scrap is recycled by remelting it.[14] The yield is approximately 67%.[22]

The high-pressure injection leads to a quick fill of the die, which is required so the entire cavity fills before any part of the casting solidifies. In this way, discontinuities are avoided, even if the shape requires difficult-to-fill thin sections. This creates the problem of air entrapment, because when the mould is filled quickly there is little time for the air to escape. This problem is minimized by including vents along the parting lines, however, even in a highly refined process there will still be some porosity in the center of the casting.[23]

Most die casters perform other secondary operations to produce features not readily castable, such as tapping a hole, polishing, plating, buffing, or painting.


See also: Casting defect

After the shakeout of the casting it is inspected for defects. The most common defects are misruns and cold shuts. These defects can be caused by cold dies, low metal temperature, dirty metal, lack of venting, or too much lubricant. Other possible defects are gas porosity, shrinkage porosity, hot tears, and flow marks. Flow marks are marks left on the surface of the casting due to poor gating, sharp corners, or excessive lubricant.[24]


Water-based lubricants are the most used type of lubricant, because of health, environmental, and safety reasons. Unlike solvent-based lubricants, if water is properly treated to remove all minerals from it, it will not leave any by-product in the dies. If the water is not properly treated, then the minerals can cause surface defects and discontinuities.

Today "water-in-oil" and "oil-in-water" emulsions are used, because, when the lubricant is applied, the water cools the die surface by evaporating, hence depositing the oil that helps release the shot. A common mixture for this type of emulsion is thirty parts water to one part oil, however in extreme cases a ratio of one-hundred to one is used.[25] Oils that are used include heavy residual oil (HRO), animal fat, vegetable fat, synthetic oil, and all sorts of mixtures of these. HROs are gelatinous at room temperature, but at the high temperatures found in die casting, they form a thin film. Other substances are added to control the viscosity and thermal properties of these emulsions, e.g. graphite, aluminium, mica. Other chemical additives are used to inhibit rusting and oxidation. In addition emulsifiers are added to improve the emulsion manufacturing process, e.g. soap, alcohol esters, ethylene oxides.[26]

Historically, solvent-based lubricants, such as diesel fuel and kerosene, were commonly used. These were good at releasing the part from the die, but a small explosion occurred during each shot, which led to a build-up of carbon on the mould cavity walls. However, they were easier to apply evenly than water-based lubricants.[27]


Advantages of die casting:[11]


The main disadvantage to die casting is the very high capital cost. Both the casting equipment required and the dies and related components are very costly, as compared to most other casting processes. Therefore, to make die casting an economic process, a large production volume is needed. Other disadvantages are:



Acurad was a die casting process developed by General Motors in the late 1950s and 1960s. The name is an acronym for accurate, reliable, and dense. It was developed to combine a stable fill and directional solidification with the fast cycle times of the traditional die casting process. The process pioneered four breakthrough technologies for die casting: thermal analysis, flow and fill modeling, heat treatable and high integrity die castings, and indirect squeeze casting (explained below).[5]

The thermal analysis was the first done for any casting process. This was done by creating an electrical analog of the thermal system. A cross-section of the dies were drawn on Teledeltos paper and then thermal loads and cooling patterns were drawn onto the paper. Water lines were represented by magnets of various sizes. The thermal conductivity was represented by the reciprocal of the resistivity of the paper.[5]

The Acurad system employed a bottom fill system that required a stable flow-front. Logical thought processes and trial and error were used because computerized analysis did not exist yet; however this modeling was the precursor to computerized flow and fill modeling.[5]

The Acurad system was the first die casting process that could successfully cast low-iron aluminium alloys, such as A356 and A357. In a traditional die casting process these alloys would solder to the die. Similarly, Acurad castings could be heat treated and meet the U.S. military specification MIL-A-21180-D.[5]

Finally, the Acurad system employed a patented double shot piston design. The idea was to use a second piston (located within the primary piston) to apply pressure after the shot had partially solidified around the perimeter of the casting cavity and shot sleeve. While the system was not very effective, it did lead the manufacturer of the Acurad machines, Ube Industries, to discover that it was just as effective to apply sufficient pressure at the right time later in the cycle with the primary piston; this is indirect squeeze casting.[5]


When no porosity is allowed in a cast part then the pore-free casting process is used. It is identical to the standard process except oxygen is injected into the die before each shot to purge any air from the mould cavity. This causes small dispersed oxides to form when the molten metal fills the die, which virtually eliminates gas porosity. An added advantage to this is greater strength. Unlike standard die castings, these castings can be heat treated and welded. This process can be performed on aluminium, zinc, and lead alloys.[16]

Vacuum-assisted high-pressure die casting

In vacuum assisted high pressure die casting, a.k.a. vacuum high pressure die casting (VHPDC),[34] a vacuum pump removes air and gases from die cavity and metal delivery system before and during injection. Vacuum die casting reduces porosity, allows heat treating and welding, improves surface finish, and can increase strength.

Heated-manifold direct-injection

Heated-manifold direct-injection die casting, also known as direct-injection die casting or runnerless die casting, is a zinc die casting process where molten zinc is forced through a heated manifold and then through heated mini-nozzles, which lead into the moulding cavity. This process has the advantages of lower cost per part, through the reduction of scrap (by the elimination of sprues, gates, and runners) and energy conservation, and better surface quality through slower cooling cycles.[16]


Main article: Semi-solid metal casting

Semi-solid die casting uses metal that is heated between its liquidus and solidus (or liquidus and eutectic temperature), so that it is in a "mushy" state. This allows for more complex parts and thinner walls.[citation needed]

Low-pressure die casting

Low-pressure die casting (LPDC) is a process developed to improve the consistency and integrity of parts, at the cost of a much slower cycle time.[35] In LPDC, material is held in a reservoir below the die, from which it flows into the cavity when air pressure in the reservoir is increased.[35] Typical pressures range from 0.3 bar (4.4 psi) to 0.5 bar (7.3 psi).[35][36] Somewhat higher pressures (up to 1 bar (15 psi)) may be applied after the material is in the die, to work it into fine details of the cavity and eliminate porosity.[35]

Typical cycle times for a low-pressure die casting process are longer than for other die-casting processes; an engine block can take up to fifteen minutes.[35] It is primarily used for aluminum, but has been used for carbon steel as well.[35]

Integrated die-casting

Integrated die-casting refers to the high-level integration of multiple separate and dispersed aluminum alloy parts through a large-tonnage die-casting machine, and then formed into 1–2 large aluminum castings. Elon Musk's team first proposed this processing method during the Tesla manufacturing process which is Giga Press program.

See also


  1. ^ For short-run zinc castings only.
  2. ^ a b c d e f g h Nitrided.
  3. ^ Die casting is an economical alternative for as few as 2,000 parts if it eliminates extensive secondary machining and surface finishing.


  1. ^ "Die Casting vs Other Processes". Archived from the original on 2016-09-23. Retrieved 2016-09-16.
  2. ^ Machinery's reference series, The Industrial Press, 1913, retrieved 2013-11-18.
  3. ^ About die casting, The North American Die Casting Association, archived from the original on 21 October 2010, retrieved 15 October 2010.
  4. ^ a b Liu, Wen-Hai (2009-10-08), The Progress and Trends of Die Casting Process and Application, archived from the original on 2012-03-14, retrieved 2010-10-19.
  5. ^ a b c d e f g John L., Jorstad (September 2006), "Aluminum Future Technology in Die Casting" (PDF), Die Casting Engineering: 18–25, archived from the original (PDF) on 2011-06-14.
  6. ^ Degarmo, p. 328.
  7. ^ Die Casting, efunda Inc, retrieved 2008-04-12.
  8. ^ a b FAQ About Die Casting, archived from the original on 21 October 2010, retrieved 12 April 2008.
  9. ^ Alloy Properties, The North American Die Casting Association, archived from the original on 2013-06-06, retrieved 2008-04-12.
  10. ^ Keller, Jeff (2021-01-12). "Larger Automotive Castings Drive Innovation in Molten Metal Delivery". Melt Pour. Foundry Magazine. Retrieved 2021-01-18. new project at a large, California-based OEM of electric vehicles. … 105 kgs of molten aluminum … delivered in each shot.
  11. ^ a b c d Degarmo, p. 331.
  12. ^ "Draft". Archived from the original on 2021-10-23. Retrieved 2016-09-16.
  13. ^ "Parting Line". Archived from the original on 2021-10-26. Retrieved 2016-09-16.
  14. ^ a b c Degarmo, pp. 329-330.
  15. ^ Parashar, Nagendra (2002), Elements of Manufacturing Processes, City: Prentice-Hall of India Pvt.Ltd, p. 234, ISBN 978-81-203-1958-5
  16. ^ a b c Degarmo, p. 330.
  17. ^ a b c d Davis 1995, p. 251.
  18. ^ a b Degarmo, p. 329-331.
  19. ^ Davis 1995, p. 252.
  20. ^ Degarmo, p. 329.
  21. ^ Schrader, George F.; Elshennawy, Ahmad K.; Doyle, Lawrence E. (2000), Manufacturing processes and materials (4th ed.), SME, p. 186, ISBN 978-0-87263-517-3.
  22. ^ Brevick, Jerald; Mount-Campbell, Clark; Mobley, Carroll (2004-03-15), Energy Consumption of Die Casting Operations (PDF), Ohio State University, doi:10.2172/822409, (US Department of Energy Grant/Contract No. DE-FC07-00ID13843, OSURF Project No. 739022), retrieved 2010-10-15.
  23. ^ Degarmo, p. 330-331.
  24. ^ Avedesian, M. M.; Baker, Hugh; ASM International (1999), Magnesium and magnesium alloys (2nd ed.), ASM International, p. 76, ISBN 978-0-87170-657-7
  25. ^ Andresen (2005), pp. 356–358.
  26. ^ Andresen (2005), p. 355.
  27. ^ Andresen (2005), p. 356.
  28. ^ Han, Q.; H., Xu. "Fluidity of alloys under high pressure die casting conditions". Scripta Materialia. 2005. 53(1): 7–10.
  29. ^ "Die Casting". 5 January 2018. Archived from the original on 2019-02-27. Retrieved 2021-06-03.
  30. ^ Dewhirst, B. "Castability Measures for Diecasting Alloys: Fluidity, Hot Tearing, and Die Soldering". Proceedings of the 4th International High Tech die Casting Conference – via HTDC. 2008.
  31. ^ "Castability Control in Metal Casting via Fluidity Measures: Application of Error Analysis to Variations in Fluidity Testing" (PDF). Archived (PDF) from the original on 2021-06-03. Retrieved 2021-06-03.
  32. ^ "Idra introduces the world's largest die cast machine". Asosiasi Italia Pemasok Foundries. 2018-02-01. Archived from the original on 2021-04-19. Retrieved 2020-04-20. capable to produce castings well beyond 80 kgs in weight over an unbeaten maximum allowed projected area. … manufacture of high-integrity Aluminium and Magnesium Die Cast components for the automotive sector, with focus on structural and safety critical components. … Injection velocity exceeding requirements of 10 m/sec
  33. ^ Bob, McClintic. "Trim Tooling, Necessary Evil, Value Added Process or Profit Opportunity" (PDF). Bob McClintic and Associates.
  34. ^ Butler, William A. (2008). "Vacuum High-Pressure die Casting". Casting. pp. 732–733. doi:10.31399/asm.hb.v15.a0005276. ISBN 978-1-62708-187-0.
  35. ^ a b c d e f Campbell, John (August 6, 2015). Complete Casting Handbook: Metal Casting Processes, Metallurgy, Techniques and Design. Butterworth-Heinemann. ISBN 9780081001202 – via Google Books.
  36. ^ "Low-pressure vs. high-pressure die casting". Kurtz Ersa Magazine. Retrieved 2023-12-10.


Further reading