VOA慢速英语:3D Printers Are Here—And They Make More Than You Think

come to mind出现在脑海中,想起

例句：I just picked up whatever goods come to mind.
      我只是想到什么就拿什么罢了。

2.A machine prints layers of material—usually plastic—one on top of the other.

on top of在…上边, 在…上方

例句：Put this book on top of the others.
      把这本书放在其他书的上边。

除…之外

例句：He lost his job and on top of that his wife left him.
      他失业了, 不仅如此, 他妻子也离开了他。

3.But high cost put them out of the reach of many researchers and businesses.

out of reach手够不着, 达不到

例句：It's out of the reach of my imagination.
      这出乎我的想象。

4.And printers are being used to create some rare parts for old machines.

be used to被用来做……

used to do过去常常做

例句：We used to do business with them on fob basis.
      我们过去和他们按船上交货价做生意。

be used to doing习惯于

例句：He is used to eating out all the time.
      他已经习惯在外面吃饭了。