Ultra Simple spool

remix from https://www.thingiverse.com/thing:3171312

精简了模型，适用于1kg以下的线材，只需要打印件和4个608轴承。
使用0.25层高 20%填充打印一套只需要3小时50分钟左右。

The model is streamline and suitable for below 1kg, only need 4 x 608ZZ bearings.
It only takes about 3 hours and 50 minutes to print a set with 20% filling of 0.25 height.