分类： Lost Foam Casting

Also known as solid casting, is one of the new casting processes in which the model made with the same structure and exact size of the castings consists of foam (EPS, STMMA or EPMMA) polymer material, after dipping refractory coating and drying, buried in the dry quartz sand by the three-dimensional vibration modeling. The polymer material is gasified and extracted when molten metal is poured into the molding box under negative pressure and then the mold is replaced by liquid metal and solidified to form casting parts.
Compared with traditional casting technology, lost foam casting has incomparable advantages, and is called as the “21st-century Casting Technology” and “foundry industry green revolution.”
Lost Foam Casting has the following characteristics: 1. good casting quality, low cost; 2, Any material, and size, are all appropriate, 3, high precision, smooth surface, reducing clean-up and saving machining; 4, greatly reducing the internal defects, casting is dense; 5, it is suitable for mass production of the same casting; 6, it is ideal for manual and automated production lines running control; 7,  it can improve the working environment and conditions of production lines, meet the environmental protection requirement. 8, reduce labor intensity and reduce energy consumption.

1. Design flexibility
Minted a highly complex casting through a combination of foam die， provides full freedom for the casting structure design.
2. Reduce manufacturing cost
Reduce the weight of rough castings, with a small allowance for machining.
3. No sand core of conventional casting
It will not occurs uneven thickness of casting due to the size inaccuracy of the sand core or the lower core position wrong.
4. High precision
Lost Foam Casting is a new process of precision molding and nearly no margin which does not need to remove the model, without sub-surface, no sand core, thus casting no flash, burrs, and draft angles and reducing dimensional errors due to core combination. The casting surface roughness can be up to Ra3.2 to 12.5μm. The casting dimensional accuracy can be up to CT7 -9. Machining allowance up to 1.5 to 2mm. So it can greatly reduce the cost of machining and can be decreased 40 % to 50% of the machining time compared with the traditional sand casting method.

Influencing Factors
Whether to adopt this process to consider the several following  factors:
1. Approximate casting materials and applicability differences are Gray cast iron – non-ferrous alloys – ordinary carbon steel – Ductile Iron – Low carbon and alloy steel.
2. The more complex structure of casting the more economic advantages of the lost foam casting process is reflected. As for a narrow channel Inner cavity and sandwich structure, the pre-experiment requires in order to put into mass production.
3. According to the size of the casting the corresponding device such as a vibration table, sandbox, etc. should be considered.

Quality Control
In the Lost Foam Casting process, pouring is the most important process. It is a vital part of producing high-quality products to strictly control the casting process at each step.
The Lost Foam Casting pouring process is the molten steel filling while the foam mold vaporizes and disappears. The whole process needs to be noted as follows:
1. Pouring path to be filled with liquid steel from beginning to end. Otherwise, it is prone to sand collapse and less intake phenomenon, causing defects.
2. To be sure steady, accurate, and fast when pouring molten steel. To be Instantaneously full of pouring cup, be fast enough to ensure continuous flow and ensure per ton of liquid poured at around one minute. If the liquid flow cuts off and causes the air taking, it may cause sand collapse, casting porosity increase, casting defects, and even casting rejection.
3. The Lost Foam Casting is negative pressure enclosed and must be enclosed at the pouring cup gate. Molten steel into the molding begins liquefied combustion and gasification. The velocity design is roughly the same for liquid steel filling and foam model disappearing.
4. After pouring is completed, hold for a period of time under negative pressure. Then negative pressure stopped, and the parts were taken out of the box after condensation.