Laboratory Assignment – Sand Casting of an Aluminium 13wt% Silicon Alloy
1) Process Attributes
Waste shown yellow*
Waste shown yellow*
After taking part in the sand casting laboratory session it was made clear that the process possessed many advantages and disadvantage, both from the process itself and from the final part produced. Observing the process step by step it was noted that the tasks carried out by the operator were not very difficult (i.e compacting sand, pouring liquid metal) and so giving the advantage of only requiring a low skill level. However, although the process did not involve a large amount of skill it was observed to be very labour intensive and took a long time to complete one cycle of the process (around 30mins). Having a long cycle time is clearly a disadvantage as time is money in the manufacturing industry but this could be slightly reduced if multiple moulds were prepared simultaneously. Another advantage observed during the sand casting procedure was that the equipment used was not very expensive and unlike other casting processes the mould was reusable. With only a low capital investment needed this would make short production runs viable. Probably the most noticeable disadvantage to the sand casting method was the low material utilization. In the labs example (seen left), almost a third of the material used is lost to the riser, runners and feeder. Particularly in today’s waste conscious culture this can cause many problems, however it can be tackled by better design.
2) Process Problems
Shrinkage: Shrinkage defects in the final product are usually the result of a feeding defect. As shrinkage naturally occurs during the solidification process, if liquid metal is not sufficiently fed through the feeding system to compensate then it will result in an indented surface. The surface defect was clearly shown in the lab example (shown left). A shrinkage defect normally occurs on
References: http://www.acetake.com http://www.rheocast.com www.electrochemsci.org/papers/vol4