There are three main types of pressure die casting: gravity, low pressure, and high pressure. Each type has its own unique benefits and drawbacks. In this blog post, we will discuss the pressure die-casting process and the pros and cons of each type of die casting so that you can decide which is the best fit for your business. Stay tuned!
Gravity Die casting
What is gravity die casting?
Gravity die casting is a type of die casting that uses the force of gravity to fill the mold with molten metal. The molten metal is poured into the top of the mold and allowed to cool and solidify. This type of die casting is typically used for large, heavy parts.
Gravity die casting’s molds are made of heat-resistant alloy steel, and the strength, size, and appearance of the aluminum castings poured out are higher than those of other casting processes
Casting process
The aluminum liquid of gravity casting is generally poured into the gate by hand, relying on the self-weight of the metal liquid to fill the cavity, exhaust, cool, opening the mold to get the die casting parts. clearing the production, heat treatment, and processing.
This kind of pressure die casting depending on force of gravity.don’t need machines
The characteristics of aluminium alloy gravity casting parts
1、The surface of the product is not good, and craters are easily produced after shot blasting.
2、The internal porosity of aluminium castings is low and can be heat treated.
3、The product has low denseness and slightly poor strength, but high elongation.
4、Lower mold cost and long mold life.
5、Low production efficiency, thus increasing the production cost.
6、The process is simpler and not suitable for the production of thin-walled parts.
7、Low fluidity special aluminium alloy can be used.
which kinds of product should choose gravity
In the product selection of what process production, mainly according to the workpiece wall thickness to make a choice, product wall thickness greater than 8mm, die-casting will cause a lot of pores stored in the wall, so the wall thickness of thicker products can choose gravity casting process to complete.
Low Pressure Die Casting
What is low pressure die casting?
Low pressure die casting is a type of die casting that uses a low pressure to fill the mold with molten metal.
Low Pressure Die casting process
In a sealed crucible (or sealed tank), dry compressed air is introduced and the metal liquid, under gas pressure, rises along the riser tube into the straight sprue and enters the cavity smoothly through the inner sprue, maintaining the gas pressure at the liquid metal level in the crucible.
This is done until the casting is completely solidified. Then the gas pressure on the liquid surface is released and the unconsolidated liquid flows back into the crucible. The mould is then opened and the die casting parts removed
This low pressure die casting method has good shrinkage, dense castings, easy casting of large thin-walled complex castings, no risers and a metal yield of 95%. No pollution, easy to achieve automation. However, the equipment costs are high and the production efficiency is low. Generally used for casting non-ferrous metals.
The characteristics of aluminum alloy low pressure parts
1, the product surface better than gravity parts,
2, Aluminum casting parts internal pore less, can be heat treatment.
3, product airtightness is high, casting strength and surface hardness is higher than high die casting, but the elongation is lower than gravity.
4、Mould cost is lower and service life is lower.
5、Production efficiency is lower than gravity and much lower than High pressure die casting.
6、The process is complex and used to produce high requirements. high accuracy and high quality castings.
7、Low fluidity special aluminium alloy can be used.
overall. low pressure is a compromise between high pressure and gravity.
High Pressure Die Casting
What is high pressure die casting?
High pressure die casting is a type of die casting that uses a high pressure to fill the mold with molten metal. this casting method in which a liquid or semi-solid metal or alloy, or a liquid metal or alloy containing an enhanced phase, is filled into the cavity of a die-casting mould at a high rate under high pressure and the molten metal or alloy is allowed to solidify under pressure to form a casting.
This type of die casting processed is typically used for high volume production , the mold can have many die cavity according requirment,
Hot chamber die casting and cold chamber are two different injection system , but for aluminum alloys , we use cold chamber
Hot chamber die casting is suitable for low melting points ,like zinc die casting
what is different of hot chamber die casting and cold chamber die casting
The crucible used to melt the metal is a hot chamber die casting if it is integrated into the die casting machine.
If the crucible for melting the metal is separate from the die casting machine, it is cold chamber die casting
High pressure Casting process
Die-casting when the commonly used pressure for 4 ~ 500MPa, metal filling speed of 0.5-120m / s. Therefore, the metal liquid filling time is very short, about 0.01-0.2 seconds (subject to the size of the casting and different) within the cavity can be filled. Therefore, high pressure, high speed is the fundamental difference between the high die-casting method and other casting methods, is also an important feature.
The characteristics of aluminium alloy die casting
1, the product surface finish is good, generally up to Ra6.3 or even up to Ra1.6.
2, Can not heat treatment.
3, product airtightness, casting strength and surface hardness, but low elongation, wall thickness is too thick easy to produce porosity.
4、High mould cost and short service life.
5、High production efficiency.
6、It can produce thin walls parts
7、It can be produced with small machining allowance.
8、It is not possible to use special aluminium alloy.
which kinds of product should choose high pressure die casting
In our actual production, high pressure die casting (cold chamber process )is used a lot, like lamps, airtight products, various auto parts
Summary
Those three types of die casting use in different area, You can choose according to your needs.
There still have many different die casting processes in the market, like vacuum die casting, semi solid die casting,squeeze casting process
The casting metals also have many , aluminum ,Znic, copper.
we will introduce more in other blog
