Sand casting is the most widespread technique in Sheet Metal Fabrication in Perth thanks to the enormous versatility of the process directly linked to the possibility of producing quality pieces with a huge variety of shapes or dimensions. It is classified according to the type of sand used: casting in organic bonded sands, cast in inorganic binder sands and cast in unbound sands.
For medium-small sized pieces, casting is carried out with the first two methods: the model of the piece to be manufactured is completely covered and the sand mechanically or chemically compacted with the binders. The molds are generally fabricated so you can easily remove the model, which will have created the cavity of the desired shape when you are going to reassemble the two parts.
In some cases it is useful to use backing, that is thin strips which, on surfaces perpendicular to the dividing line of the bivalve mold, facilitate its opening. This arrangement is particularly suitable in the presence of pieces of different material destined to be removed by casting said so-called cores adapted to create cavities inside the final object.
The size of the mold must always be slightly higher than that of the desired piece so that no problems occur during the contraction of the metal in cooling, moreover it must be taken into account the possibility of inserting additional melt input channels, feeders, precast concrete, sprues to make the flow of metal in the mold more homogeneous.
The tolerances on the measurements are a priori calculated by the modeller on the basis of parameters derived from his own experience and considerations on the casting alloy. The choice of the type of model and the material with which to build it are a function of different factors such as the type of casting, the number of pieces to be produced, the desired tolerance and the cost.
The construction materials of the commonly used models are wood, metal or plastic polymers. Wood is certainly the most economical and easy to model, but has poor mechanical characteristics, on the contrary metal is more expensive but durable thanks to its clearly improved mechanical characteristics; plastic polymers are more recently developed and represent an excellent compromise between cost and quality.
In order to optimize the design of the mold, casting simulation software is very useful, able to reproduce the working conditions allowing a more detailed evaluation. When preparing the mold, pay close attention to the uniformity of the sand and to the distribution of the binder if present: if in some places the material is too dry, too wet or there is an excess or defect of binder, the surface finish is worsened.
Leave a Reply