We use cookies to give you the best experience on our website. If you continue without changing your settings we will assume you are happy to receive all cookies Find out more. While the ability to reduce physical weight has been a key driver behind increased demand for aluminium and other light alloy parts in recent years — properties including electrical and thermal conductivity, mechanical strength, corrosion and resistance are also attracting the attention of manufacturers in a multitude of industries.
Due to this unique range of characteristics, light metal can be used to cast complex, safety-critical components in automotive, electronics and aerospace. It also offers a cost-effective production option for simple parts from lighting components to kitchen tools. To produce light alloy castings, three of the most common technologies are: high pressure die casting , gravity die casting and low pressure die casting.
Each technology can support permanent casting process with gravity and low pressure also able to support semi-permanent casting processes. In a permanent process, the metal die mould is re-usable. In a semi-permanent casting process, the metal die also incorporates one or more sand cores that will form internal passages within the final casting. The main advantage of both permanent and semi-permanent casting is the suitability for process automation and large-scale production, making the techniques popular with high volume manufacturers.
For example, the die for a part which requires 3 side-core directions can only contain 2 cavities. There is no direct cost added, but it is possible that the use of more cavities could provide further savings. Login Register for free!
Die Casting. Contents 1. Capabilities 2. Process Cycle 3. Equipment 4. Tooling 5. Materials 6. Possible Defects 7. Design Rules 8. Cost Drivers. Die casting hot chamber machine overview Die casting cold chamber machine overview. Max wall thickness : 0. Disclaimer: All process specifications reflect the approximate range of a process's capabilities and should be viewed only as a guide.
Actual capabilities are dependent upon the manufacturer, equipment, material, and part requirements. Clamping - The first step is the preparation and clamping of the two halves of the die. Each die half is first cleaned from the previous injection and then lubricated to facilitate the ejection of the next part.
The lubrication time increases with part size, as well as the number of cavities and side-cores. Also, lubrication may not be required after each cycle, but after 2 or 3 cycles, depending upon the material.
After lubrication, the two die halves, which are attached inside the die casting machine, are closed and securely clamped together. Sufficient force must be applied to the die to keep it securely closed while the metal is injected. The time required to close and clamp the die is dependent upon the machine - larger machines those with greater clamping forces will require more time.
This time can be estimated from the dry cycle time of the machine. Injection - The molten metal, which is maintained at a set temperature in the furnace, is next transferred into a chamber where it can be injected into the die. The method of transferring the molten metal is dependent upon the type of die casting machine, whether a hot chamber or cold chamber machine is being used. The difference in this equipment will be detailed in the next section.
Once transferred, the molten metal is injected at high pressures into the die. Typical injection pressure ranges from 1, to 20, psi. This pressure holds the molten metal in the dies during solidification. The amount of metal that is injected into the die is referred to as the shot. The injection time is the time required for the molten metal to fill all of the channels and cavities in the die.
This time is very short, typically less than 0. The proper injection time can be determined by the thermodynamic properties of the material, as well as the wall thickness of the casting.
A greater wall thickness will require a longer injection time. In the case where a cold chamber die casting machine is being used, the injection time must also include the time to manually ladle the molten metal into the shot chamber.
Cooling - The molten metal that is injected into the die will begin to cool and solidify once it enters the die cavity. When the entire cavity is filled and the molten metal solidifies, the final shape of the casting is formed.
The die can not be opened until the cooling time has elapsed and the casting is solidified. The cooling time can be estimated from several thermodynamic properties of the metal, the maximum wall thickness of the casting, and the complexity of the die. A greater wall thickness will require a longer cooling time.
The geometric complexity of the die also requires a longer cooling time because the additional resistance to the flow of heat. Ejection - After the predetermined cooling time has passed, the die halves can be opened and an ejection mechanism can push the casting out of the die cavity.
The time to open the die can be estimated from the dry cycle time of the machine and the ejection time is determined by the size of the casting's envelope and should include time for the casting to fall free of the die. The ejection mechanism must apply some force to eject the part because during cooling the part shrinks and adheres to the die.
Once the casting is ejected, the die can be clamped shut for the next injection. Trimming - During cooling, the material in the channels of the die will solidify attached to the casting. This excess material, along with any flash that has occurred, must be trimmed from the casting either manually via cutting or sawing, or using a trimming press.
The time required to trim the excess material can be estimated from the size of the casting's envelope. The scrap material that results from this trimming is either discarded or can be reused in the die casting process. Recycled material may need to be reconditioned to the proper chemical composition before it can be combined with non-recycled metal and reused in the die casting process. Die cast part Return to top. Hot chamber die casting machine - Hot chamber machines are used for alloys with low melting temperatures, such as zinc, tin, and lead.
The temperatures required to melt other alloys would damage the pump, which is in direct contact with the molten metal.
The metal is contained in an open holding pot which is placed into a furnace, where it is melted to the necessary temperature. The molten metal then flows into a shot chamber through an inlet and a plunger, powered by hydraulic pressure, forces the molten metal through a gooseneck channel and into the die.
Typical injection pressures for a hot chamber die casting machine are between and psi. After the molten metal has been injected into the die cavity, the plunger remains down, holding the pressure while the casting solidifies. After solidification, the hydraulic system retracts the plunger and the part can be ejected by the clamping unit. Prior to the injection of the molten metal, this unit closes and clamps the two halves of the die.
When the die is attached to the die casting machine, each half is fixed to a large plate, called a platen. The front half of the die, called the cover die, is mounted to a stationary platen and aligns with the gooseneck channel. The rear half of the die, called the ejector die, is mounted to a movable platen, which slides along the tie bars.
The hydraulically powered clamping unit actuates clamping bars that push this platen towards the cover die and exert enough pressure to keep it closed while the molten metal is injected. Following the solidification of the metal inside the die cavity, the clamping unit releases the die halves and simultaneously causes the ejection system to push the casting out of the open cavity.
The die can then be closed for the next injection. Hot chamber die casting machine - Opened Hot chamber die casting machine - Closed. Cold chamber die casting machine - Opened Cold chamber die casting machine - Closed. Die channels The flow of molten metal into the part cavity requires several channels that are integrated into the die and differs slightly for a hot chamber machine and a cold chamber machine.
Materials Properties Aluminum alloys Low density Good corrosion resistance High thermal and electrical conductivity High dimensional stability Relatively easy to cast Requires use of a cold chamber machine Copper alloys High strength and toughness High corrosion and wear resistance High dimensional stability Highest cost Low die life due to high melting temperature Requires use of a cold chamber machine Magnesium alloys Very low density High strength-to-weight ratio Excellent machinability after casting Use of both hot and cold chamber machines Zinc alloys High density High ductility Good impact strength Excellent surface smoothness allowing for painting or plating Requires such coating due to susceptibility to corrosion Easiest to cast Can form very thin walls Long die life due to low melting point Use of a hot chamber machine The selection of a material for die casting is based upon several factors including the density, melting point, strength, corrosion resistance, and cost.
Return to top. Defect Causes Flash Injection pressure too high Clamp force too low Unfilled sections Insufficient shot volume Slow injection Low pouring temperature Bubbles Injection temperature too high Non-uniform cooling rate Hot tearing Non-uniform cooling rate Ejector marks Cooling time too short Ejection force too high. The molds—also known as tools or dies—are created using steel and are specially designed for each project.
This allows each component to be created with accuracy and repeatability. Aluminum, zinc, and magnesium are the most commonly used die casting alloys. Die casting can have significant advantages over other manufacturing processes, which often lead to major cost savings, not only in the part price itself but also in the overall cost of production. When you cast a part, you can create complex net shapes, including external threads and complex internal features with minimal draft angles—minimizing secondary operations.
You can also combine multiple parts into a single part, eliminating assembly operations and lowering labor costs, with the added benefits of simplified stock control and greater component consistency. Zinc, aluminum, and magnesium are the three main die casting alloys. They are normally non-ferrous and their mechanical properties vary greatly to fit almost every type of application a manufacturer may need. Not only can die cast alloys withstand high operating temperatures, but they are also fully recyclable.
Die cast alloys also have:. Separately, each die cast alloy offers a variety of benefits that the other may not offer. That is one of the great things about die casting, you do not have to be limited when it comes to choosing the right metal.
Each project is different which is why Dynacast offers multiple solutions for all die casting needs. This ensures the right process is always used for the right application. At Dynacast, we offer three different types of die casting processes. Used for zinc, some magnesium alloys, and other low-melting, hot-chamber die casting is a great option for alloys that do not readily attack and erode metal pots, cylinders, and plungers.
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