This question is very interesting. In the early days, many scientists wanted to study this technology.In theory, this technology is capable of doing today's technologies. Today's printing accuracy, including materials, etc., is not a problem. However, technology is not widely used. There may be many potential problems. It may be due to practicality, or cost, or other reasons.
From another point of view, the 3D printer itself is a "self-replicating machine", so copying itself should also be no problem, but the current level of technology is not enough.
I have found an article. If you are interested, you can check it out. In theory, self-replicating 3D printers are the same as self-replicating robots. http://www.biso.cn/html/1161.htm?utm_medium=s