EPC casting refers to the process in which the model vaporizes disappears. The model here refers to the mold used in casting, referred to as EPC casting.  Ordinary sand casting is to pour metal liquid into a specific mold remove the mold after the metal liquid forming to form the desired casting.  The lost mode casting process is different this one. In the lost mode casting process, the mold is made of foam plastic buried in the sand mold. The sand mold usually uses dry sand dry sand with binder, which is treated by vibration suction negative pressure, then filled with metal liquid.  The high temperature liquid metal heats up the foam, which is softened, liquefied vaporized to form the casting.

1 Characteristics of epc process

Using epc castings of high precision technology, basic no machining allowance, because of lost foam casting technology is a new type of precision forming process, this process is don't need to take out the characteristics of wood samples, compared with the ordinary casting process without the parting surface, no sand core, adopts the method of casting the large machine equipment there is no flash burr, no draft Angle,  Greatly reduce the size error caused by the core combination matching.

Compared with ordinary large machine equipment casting, lost foam casting process design more flexible, casting structure design, more liberty using ordinary way of casting, large, complex casting machine equipment need to separate all parts manufacturing equipment, splicing assembled again, using epc process in which it is, you don't need to bubble for Mosaic,  Thus, the casting process assembly difficulty are greatly simplified.  The difficulty of machining is reduced, manpower material resources are saved, casting quality is improved economic benefit is enlarged.

The lost mode casting process does need to use the sand core in the traditional casting process. The lost mode casting process uses dry sand to enrich compress, relies on the flow of dry sand to produce the inner cavity hole of the casting. Therefore, the problem of the inaccurate size of the sand core does exist in the large coal machine equipment of lost mode casting, also avoids the problem of the inaccurate position of the lower core.

Epc process also has the advantages of clean environmental protection in the process of casting large machine equipment, no chemical binder in green sand, foam plastic is harmless to the environment, in the process of lost foam casting large machine equipment, very few emissions of harmful substances, emissions only relatively concentrated discharge location, easy to collect discharge time is short.  Dry sand molding is adopted in the mold of lost mold, the amount of sand falling in the casting is significantly reduced.  At the same time, the input of personnel workload the workload of cleaning have been significantly reduced.  Noise reduction dust control are improved in the casting process of large coal machine.

Another characteristic of lost mode casting process is that it can improve the economic benefit. Because of the lost mode process, the sand recovery rate is high, the amount of chemical adhesive is less, the waste is less.  The increased degree of automation reduces the input of manual labor improves the production environment.

2. Problems faced by coal machine equipment

Machine equipment industry is now facing the problem of market turmoil, the competition there is no perfect mechanism, maintenance of state-owned enterprises, private enterprises, foreign-funded enterprises, enterprises are doing large machine equipment, many parts of the machine equipment companies density is larger, large machine equipment parts city, with large coal equipment manufacturing manufacturers, large machine equipment without strict industry standards,  Without a standard pricing mechanism, many companies compete on price, dragging down the quality of manufacturing processes.

In the production of coal machine equipment accessories, there are still some problems, such as backward manufacturing technology, single testing experimental means, old processing equipment so on.  Now, China's mechanical basic processing means backward, casting technology can be innovative, heat treatment welding quality can meet the requirements of frequent problems, performance parameters are still a long way to go the design requirements.

3 Application of lost mold casting technology in large coal machine

3.1 Foam plastic appearance manufacturing

The appearance manufacturing of lost mold is the most important in the process of lost mold casting. The material selection, manufacturing method technology of lost mold should be paid enough attention to.  The production of lost mold should mainly meet the following requirements, the gasification temperature should be low, so that the lost mold can be more easily gasification decomposition.  Gas emission should be low, so as to reduce decomposition products.  Gasification is fast complete, the residue after gasification should be as little as possible.  The weight reduction of vanishing die itself is beneficial to transportation manufacturing, to casting.  Material strength stiffness should be as high as possible to reduce damage during transportation use.  Good structural stability of the model can produce excellent quality molds.  In the process of mold making, we should be familiar with the design content design ideas of the drawings, modify the design drawings manufacturing process flow of the lost mold timely, so as to make a reasonable mold.

3.2 Case study on the application of lost mold in the production of large coal machine equipment accessories

Under the condition of negative pressure, the lost mold casting technology was used to improve the fluidity of molten metal, the exhaust port was arranged scientifically reasonably, the vertical shaft crown wheel with a weight of 2.5 tons a diameter of 3 meters was successfully cast, which realized the expected design purpose.  The main advantage of epc process in the production of large coal machine is that the fluidity of molten metal liquid becomes better under the condition of negative pressure, it also solves the problem of original sand mold collapse.