N < 1000 because zinc dies wear in the 100s of parts
Graph legend (CED: MJ/part)
CED (MJ/per part)：
1. CED = Cumlative Energy Demand, also known as embodied energy.
2. All dies are cast and machined zinc except the superplastic forming die which is cast and machined iron.
3. The Superplastic Forming graph always assumes the use of SP5083 alumnium sheet.
4. The forming processes examined in this study are not perfect substitutes for each other. For example, simple stretch forming cannot be used to make sharp concave features on the outside of parts, whereas SPF, which can produce complex shapes in one process step, cannot be used to produce parts at the same rate as matched die-set drawing. If designers wish to directly compare the impacts of one process to another they should consider the different capabilities of each process.
5. In the case of Stretch Forming, the batch number B equals production number N. And in the case of Superplastic Forming, for N<100, B=N, otherwise B=100.
Created by Jiawei Song