1. Sand casting is preferred
According to statistics, 60% ~ 70% of the castings in our country or in the world are made of sand, and about 70% of them are made of clay sand. The main reason is that sand casting costs less than other casting methods, the production process is simple, and the production cycle is short. So like a car engine cylinder block, cylinder head, crankshaft and other castings are made of clay wet sand process. When the wet type can not meet the requirements and then consider the use of clay sand table dry sand, dry sand or other sand. Clay wet sand castings can weigh from a few kilograms to tens of kilos, while clay dry castings can weigh tens of tons.
In general, for medium and large castings, cast iron can be made of self-hardening resin sand cast steel can be used to produce sodium silicate sand mold, you can get a precise size, smooth surface casting, but the cost is higher.
Of course, castings produced by sand casting tend to have poor casting accuracy, surface finish, material density and microstructure, as well as mechanical properties, so other casting methods such as fusing Wax) casting, die-casting, low-pressure casting.
2. Casting method should be compatible with the production batch
For example, sand casting, mass production of the factory should create the conditions for the use of advanced technology modeling, core method. Old-style shock or vibration pressure molding machine production line productivity is not high enough, workers labor-intensive, noisy, does not meet the requirements of mass production, and should be gradually transformed. For small castings, you can use horizontal or vertical sub-type box-free high-pressure molding machine production line, real modeling and high production efficiency, covers an area of less; for the pieces can choose a variety of high-pressure molding machine production line, gas Chong shape line to meet the requirements of fast, high-precision modeling production line, core method can be used: cold core box, hot core box, shell core and other efficient core method. Large batch of medium-sized castings can consider the use of resin molding sand and core.
At this stage, the labor costs are increasing, and casting workers are getting tighter day by day. Therefore, it is an inevitable direction for the development of the foundry industry that the relatively single and batch-sized products give priority to the automatic molding line. Many products are more single and the accuracy and quality of the casting High demand for small and medium-sized castings should give priority to iron-based sand filling automated production lines (such as: crankshaft, wheels, brake drums, casting balls, etc.).
Small single-piece production of heavy castings, hand molding is still an important method, manual modeling can adapt to a variety of complex requirements more flexible, does not require a lot of technology and equipment. It can be applied to water glass sand type, VRH water glass sand type, organic ester water glass self-hardening sand type, clay dry type, resin self-hardening sand type and cement sand type, etc. For single-piece heavy-duty castings, the pit modeling method has low cost and put into production fast. The mass production or long-term production of stereotypes products using multi-box modeling, split box modeling method is more appropriate, although the mold, sand box, etc. began to invest high, but can save the modeling man-hours, improve product quality compensation.
Low-pressure casting, die-casting, centrifugal casting and other casting methods, due to equipment and mold expensive, so only suitable for mass production.
3. Modeling methods should be suitable for factory conditions
For example, the same is the production of large machine bed and other castings, the general use of core shape method, does not make the appearance and sand box, pit in the core group; and the other factory uses the sand box modeling method, making appearance. Different business conditions (including equipment, venues, staff quality, etc.), production habits, the experience accumulated vary, these conditions should be considered for what products do not fit (or cannot) do what products.
4. To take into account the accuracy of casting requirements and costs
Casting obtained by a variety of casting methods of different precision, initial investment and productivity are inconsistent, the final economic benefits are also different. Therefore, to achieve more, faster, better and more economical results, we should take all aspects into account. Initial selection of the casting method should be carried out to estimate the cost, in order to determine the casting method with high economic benefit and with guaranteed casting requirements.