You could save weight of parts needed to be transported to space. Here's my reasoning: backups / spares There are an enormous number of backup parts on the IS

You could save weight of parts needed to be transported to space. Here's my reasoning: backups / spares There are an enormous number of backup parts on the ISS – there needs to be for any manned space vehicle – to fix systems that fail. Instead of wasting weight, fuel & money on lifting multiple spares to the ISS, one could 3D print them on demand. Not all spares will be needed simultaneously.