DESIGNING OF A GEAR HOUSING
The objective is formulating a suitable solution for a customer for gear housing.
The component will be produced in batches of 500 every two months. The production is a medium production, not a mass production.
Considering all the information given the best solution must be carry out. At the same time the solution must be suitable with all the final characteristics of the piece and economically profitable.
It is already known that the initial geometry of the piece is the result of a casting process.
The most suitable casting process must be selected and all the subsequent process operations must be chosen to obtain a piece with the requested characteristics. But, first of all, the material must be chosen. This choice will strongly influence the manufacturing processes which could be used.
The solution to be economically profitable must reduce the material used and therefore reduce the cost of the material which is a big part in the total cost.
2. Design consideration for casting
The sketch of a casting piece mustn't present sharp edges and the thickness of the sections must be as constant as possible.
These because when the material is poured in to the mould if there are sharp edges and corners could be problems.
The metals and the metal alloys suitable for casting processes must have good fusibility and melting proprieties.
They must filling completely the mould and therefore have a good fluidity, maintaining a sufficient structural homogeneity during the solidification.
Thanks to a good design of the piece is possible avoid all that bad effects which could be present during the solidification and the cooling process.
Examples of these defects are:
cavity of withdrawal
tension of withdrawal
formation of hot bunch
The sketch of the piece for the casting process is different from the finished piece.
During the process of solidification the volume of the material decreases and to compensate this some alimentations are inserted. But during the cooling process the volume of the material decreases further, to avoid this volumetric contraction the dimensions of the piece must be bigger than that of the finished piece.
In almost all the casting process at the end it is necessary working some of the faces of the piece to remove the metal shavings. For this motivation a stock must be considered.
The values of the stocks depend on the materials.
In the sketches angles of must be considered to permit the extraction of the piece from the mould.
A consideration for the re-design must be done to reduce the weight of the piece. A way to reduce the amount of the material used in the casting could be the scalloping.
3. Selection of materials and processes
The selection of the material and that of the manufacturing processes are strongly linked together. Therefore this part of the design is crucial for all the...