Foundry processes for metal billets are organized in various ways. As the resulting product, a lot depends on the characteristics of the basis on which the object is modeled, that is, on the shape that takes the fill of the future workpiece material. One of the most popular technologies is sand-clay molding, which gives many advantages. The method is quite old, but it is actively used in industries of various levels - from small workshops to large enterprises.
Technology Overview
The injection process is a technical procedure, as a result of which a preform or an already finished product with the necessary geometric parameters is formed from molten metal. To achieve the required shape, a model corresponding to the requirements is used. The bearing base for casting in this case is the sandy clay form. It is formed by two groups of components. The first includes zirconium and quartz sand, and the second includes kaolin and bentonite clay. Thus, a combination of one-time equipment is formed, which in the process of work takes the material of the future workpiece. But these are not all the components on the basis of which sand-clay molds are realized. The technology is not complete without a model kit, which is a kind of example of future procurement. For such modeling soft-bodied or malleable materials are used in machining - for example, wood or light metals. However, the soft body base is used only in those cases when it is necessary to duplicate the target part. But it happens that the craftsmen are already dealing with finished products, the parameters of which need to be repeated through casting. Now it’s worth moving directly to the benefits of this technology.
Variety of shapes
The complexity of using most molds and models for casting lies in the fact that the technology does not provide for the destruction of their structure. This significantly limits the methodology of the operation, complicating the functions of workers. In the case of sand-clay forms, such restrictions do not exist, since the method initially involves a one-time use of the form. However, this does not mean at all that reusable use of equipment is fundamentally excluded. For reasons of economy, the form can be applied serially if it does not contradict the requirements for the final result of the process. The technical and organizational advantages of sand-clay molding are largely determined by the approach to the practical part of the implementation. In the case of all-in-one equipment, you can count on removing the mold without damaging it, as well as receiving a cast with the necessary parameters. This option is often used in working with simple castings. But if we are talking about workpieces that are complex in design, then a split, collapsible form is used, for which there are just no restrictions in terms of the parameters of the desired product.
Process Availability
An example of the use of sand molds for casting demonstrates how much more profitable are traditional manufacturing techniques compared to modern ones. In this case, this is due to the simplicity of the organization of casting. For the operation you need only a set of the above materials for the form and modeling equipment, which also does not require complex procedures. Elementary models for molding can be made of wood with a carpentry tool. Unless in critical industries, in the manufacture of complex castings, additional means of processing and impregnating this material are also involved. Sand-clay molds made of metal and plastic are also complex. But, again, this applies to specialized industries. Practice shows that in the world about 80-90% of all castings are made on the basis of the simplest capacities in the form of improvised tools and traditional drying chambers.
Economic expediency
Typically, the use of one-time equipment involves the cost of the process. Therefore, such decisions are addressed only in extreme cases, if it is necessary to manufacture parts or designs of non-standard shapes. But foundry is showing the opposite trend. Sand-clay casting pays off financially, even in cases where a destructible base is used. This can be explained by the minimal costs for the form itself and for the modeling structure.
Technology versatility
There are few manufacturing aspects that could limit the scope of this technology. It is used in industry, construction, small-scale and single-piece manufacturing of hardware, in private workshops, etc. Unless specialized high-precision production lines do not allow this process, since it does not allow to ensure the proper level of accuracy of the workpiece characteristics. But from the point of view of the use of metal melts, universality is noted, which distinguishes casting into sand and clay forms against the background of other technologies. Briefly reflect unacceptable metals can be used by a group of refractory alloyed species. Traditional cast metals are quite suitable for use in this molding operation.
Possible casting defects
The weak point of this technology, as mentioned above, is the low accuracy in the parameters of the workpiece. Products are rough, not always symmetrical and with the presence of individual defects. This nuance is the flip side of the rudeness and simplicity of obtaining a snap. In addition, sand-clay casting allows for the risk of non-metallic inclusions entering the composition of the casting. Depending on the metal itself, gas porosity may also occur. But this does not mean at all that defects become a serious obstacle to the widespread use of sand molding technology. You can compensate for this drawback by observing the rules of quality casting.
Recommendations for obtaining high-quality workpiece
Technologists are advised to adhere to two basic rules that will allow you to get closer to obtaining the expected result. First, you should avoid using the method in conditions of low fluidity of the metal. The fact is that a high cooling rate can contribute to intensive cooling and melt, which causes the formation of junctions and underfills. The second nuance, without which professional casting into one-time sand-clay molds is not complete, concerns holding a small tolerance on the volume of the workpiece. The increase in the initial parameters in the future will allow you to mechanically modify the product without the risk of irreparable damage.
Conclusion
The technology is simple and affordable, but this does not mean that it does not imply development. In some areas, sand-clay mold casting is also being modernized, which allows to optimize the process and eliminate some of its shortcomings. The most noticeable and promising branch of the method is considered to be evacuated forms. The principles of using sand remain the same, however, the clay group of components as a bonding base is excluded in this case.