Try the technique before you buy with a DIY alternative. Roll a sheet of black card into a cone and place a strip of black or gaffer tape along the seam to hold it securely in place.
在买之前先自己DIY一个，把一张卡纸卷成圆锥型，用电工黑胶粘牢。
2
A cylinder connected to a cone is often met in sheet metal work.
园柱管与园锥相接合，在钣金工作中是经常遇到的。
3
In this paper, a cone - type curve flattening equation commonly used in engineering technology is presented for applications of sheet metal processing in mechanical manufacturing process.