The comparison of lost foam casting and other casting methods-The maximum characteristics of lost foam casting.

The maximum characteristics of lost foam casting. It adopts EPS or STMMA foam plastic as materials. By pre-foaming, modeling and combination into model clusters, we bury it in the dry sand. By vibration and compaction, it casts the metal liquid under the negative pressure impact. The high temperature metal liquid makes the model vaporize. The gas vaporized is discharged by coating layer and dry sand. The metal liquid is replaced. After solidification, it becomes castings. From picture 1-2, we can see that the lost foam casting process has following advantages compared to other casting processes,

① The model material is EPS or STMMA

②It saves the core box production process, core production process and baking paint production process without core setting process.

③ In the modeling process, it doesn’t need these complex processes, such as pattern lifting, model modification or mould assembling.

④The castings produced have no flash or burrs, and the amount of cleaning required is greatly reduced.

⑤The process is flexible. It can realize many castings in one box and inlay casting and so on.   

The above points make the lost foam casting have great advantages in the model production material process, modeling process and clean labor .

(1) For casting material application, generally speaking, all alloys which can be used for casting can be used for lost foam casting. The application exceeds sand casting. The ordinary sand casting can’t cast titanium alloy . However, the lost foam casting casts the titanium alloy by adopting Si sand. At present, the materials by lost foam casting production include ordinary cast steel, heat resistance alloy steel,stainless steel, ferro-nickel alloy, ordinary gray cast iron, abrasion resistance cast iron, white cast iron, heat and abrasion resistance castings,ductile cast iron,alloy, copper alloy and so on. For high melting point casting alloy material, the burnt-on sand on the surface is little without fins and rags. It is easy to clean. The casting basal body is uniform.

(2) For casting size application, the vibration table working surface size and sandbox size(length*width*height) will directly decide casting size and quantity by lost foam casting.Therefore, for casting application, it is much more extensive than that of sand casting. It can put different size of sandbox on vibration table working surface. Therefore, it is very convenient to arrange all castings（it includes set of small clusters and clusters arrangement) in the sandbox. It can cast several kilos(or less than 1kilos of clusters) of castings. It can also cast 1 kilos (more than) casting(according to medium frequency stove capacity), such as support seat,(ZG 35) small hammer, grate bar and 1 ton HT 250 table surface and oil cylinder base seat and so on. Altogether, large piece depends on melting medium frequency furnace capacity. The small piece depends on sandbox size to make clusters. The arrangement is flexible and changeable.  

(3) For casting’s all structures application: the lost foam casting’s process characteristics is especially appropriate for complex structure(complex inner cavity interlayer, blind hole, bending transition cavity and so on). For the problems that model parting is difficult and modeling is difficult, it should avoid the difficulty of large flat surface upwards. Castings that are difficult to make cores for ordinary sand casting and complex on parting surface such as stockings series, cylinder body, propeller, water pump impeller,shell and more complex structure model core castings, such as automobile engine cylinder block, cylinder cover and manifold of air inlet and so on.

(4) It applies for casting’s single and big batch of production. The lost foam casting will consume one foam plastic model(EPS, STMMA or EPMMA) when it casts one casting. For batch production, it must consider the mould cost to produce plastic white model. For instance, to produce the high speed road guardrail support bracket(ZG 35) needs dozens of tons or hundreds of tons. And this requirement is constant. Therefore, it is best that the EPS particle foam mould becomes the model. It is same with the high chromium cast iron hammerhead of abrasion resistance castings. However, for the single piece, two pieces, three pieces or more, but small quantity of pieces, it uses EPS material to cut, machine and bond. Because the model(white model) can be made by manually or by particle foam mould modeling to produce white models, the application is flexible.

(5) The lost foam casting’s quality advantage. From the production process flow, we could see the model production process of lost foam casting is similar to the wax foam precision casting. The casting is similar to the V method casting. The modeling is similar to full mold casting. Therefore, the modern lost foam casting technology combines with advantages of full mold casting, V-method casting and precision casting.

Due to the unique characteristics of lost foam casting, it reduces the size error due to model core combination. The casting size precision and surface roughness can reach CT5～CT7、Ra6.3～12.5μm，within sand casting and wax casting. Because sand filling adopts the dry sand, it removes the defects due to water, binder or additives. The casting rejection rate is decreased. The casting quality is improved greatly. Picture 1-2 is the casting’s surface roughness comparison of castings by lost foam casting and castings by other casting process method.

Table 1-2 The comparison of several castings surface roughness

(6)The lost foam casting is easy to realize clean production. In the low temperature condition, the EPS organics emission load only accounts for 0.3% of casting metal liquid quality; the self-hardening sand is 5%. At the same time, the organic emission time is short; the location is concentrated and it is easy to collect. It can adopt the negative pressure suction-inhale type burning-- purification treatment. The product burnt and cleaned is no harm to the environment. The old sand’s reuse rate is more than 95%. Compared to the traditional casting method, EPS method has lower noise and dust harm. The worker’s labor strength is reduced greatly and the labor environment is improved obviously. It is easy to realize mechanization, automation and clean production.