Lost foam casting (that is, EPC process) is a new process with nearly no margin and precise molding.
Four advantages of lost foam casting
Dimensional accuracy and surface roughness approaching that of investment casting
Since the easy-to-gasify foam plastic is used as the pattern, there is no need to take the mold, no parting surface, no mud core, so there is no flash burr, no draft angle, and the size error caused by the combination of core blocks is reduced. Accuracy and surface roughness approach investment casting.
Because the lost foam casting adopts dry sand molding, the defects caused by water, binder and other additives in the molding sand are eradicated, and the casting rejection rate is significantly reduced. In particular, this process does not require high technical level of operators.
Lost foam casting is easy to achieve clean production. The organic matters produced by the decomposition of the pattern during pouring are less, and the discharge of organic matter only accounts for 0.3% of the weight of the pouring molten iron, while the organic matter in self-hardening sand accounts for 5%. At the same time, the time for generating organic matter is short, and the centralized location is easy to treat and discharge through negative pressure suction, so as to realize pollution-free discharge to the environment. In addition, the recovery rate of old sand is over 95%, which saves the operating system for sand casting and recycling of old sand, and reduces the harm of quartz powder.
The development of lost foam casting technology provides sufficient freedom for the structural design of castings. Components that were originally processed and assembled by multiple parts can be molded in pieces and then bonded together to cast them as a whole. The holes and holes that originally needed to be processed can be cast directly, which greatly saves processing costs and can also reduce processing costs. Cost, but also can reduce processing equipment investment. Generally speaking, the EPC process can reduce equipment investment by 30% to 50%, and casting costs can be reduced by 10% to 30%.
The superiority of lost foam casting is unquestionable. It conforms to the general trend of casting technology development and has broad development prospects.
Selection of Raw Materials for Foam Plastic Models
In order to obtain high-quality lost foam castings, the following key technologies must be paid attention to, namely, the selection of raw materials for foam plastic models: pattern forming technology and equipment, coating and coating methods: dry sand filling and compaction, alloy smelting technology and casting schemes, etc.
Among them, the development of pattern materials and pattern manufacturing are particularly important. First of all, there is lost foam (full mold) casting technology only when there are pattern materials, and the development of lost foam casting technology requires pattern materials with better performance, and the development of new pattern materials promotes the development of lost foam casting technology. .
From ordinary packaging EPS to the development of special EPS beads for lost foam, from EPS pattern materials to a new generation of pattern materials EPMMA and styrene and methyl methacrylate copolymer materials have been successfully developed, making the lost foam casting process from non-ferrous metal castings to black castings. The production of metal castings, from gray cast iron to ductile iron and steel castings, from ordinary steel castings to the development of low carbon steel, alloy steel and stainless steel castings, has made the lost foam casting technology more mature and perfect.
The development of lost pattern materials in China started relatively late. Since the early 1990s, after more than ten years of hard work, various technical difficulties have been overcome, and three special shape materials for lost foam, EPM-MA, EPS and STMMA, have been successfully developed.