ABronyAccount 
[@Dsiak](/images/2907518#comment_10172347)
It's a machine that you fill with goop and it zaps it with cancer-rays which turns the goop into little solid plastic doodads, one layer at a time.
There's an LCD screen between the goop and the cancer rays, and its picture casts a shadow everywhere that you don't want the cancer rays to zap the goop. This way, only the parts of the goop that you want to zap with cancer rays harden into a layer of the doodad.
But because the cancer rays are super intense, the screen it uses to mask out the patterns for the doodads eventually wears out. So they have to be replaced after a while.
It's a machine that you fill with goop and it zaps it with cancer-rays which turns the goop into little solid plastic doodads, one layer at a time.
There's an LCD screen between the goop and the cancer rays, and its picture casts a shadow everywhere that you don't want the cancer rays to zap the goop. This way, only the parts of the goop that you want to zap with cancer rays harden into a layer of the doodad.
But because the cancer rays are super intense, the screen it uses to mask out the patterns for the doodads eventually wears out. So they have to be replaced after a while.