In reference to the patent: US20160332236 Several published articles of previous work into AM of cutting tools existed long before the application of this patent was even thought of. The "inventor" does not even have one article or publication related to AM. Does that not then constitute as plagiarism or copyright infringement? Then why did the US, Chinese, and German patent offices grant the patent?
What you linked to is not a US patent. It is a patent application. It may never get to be a patent. You can use the US Public Pair site to determine the status of this application. At this point, the application is still not granted. The latest communications from the examiner is: "Final Rejection Mailed" on 07-10-2017. Final rejections aren't necessarily completely final, so there is likely still some ability to appeal or amend the claims. The links to the German and Chinese versions are likewise only applications at this point.
Then why did the US, Chinese, and German patent offices grant the patent?
Again, you need to be aware that patent applications are published typically 18 months after filing. The fact that an application publishes does not indicate that it will ever be granted as a patent. Indeed, it is very likely even if the patent is granted, the claims will be narrowed. I will also say, that just because the inventor hasn't published does not mean he can't invent anything of value. Many inventors that work for commercial companies don't publish their work. Indeed publishing before filing for a patent can keep you from obtaining the patent. Also even if there is substantial prior art in a field, it doesn't mean new inventions are impossible. Even a subtle improvement on an existing technology can be granted a patent. I won't comment on the specific application you cited, but it helps to actually see the figures which your link doesn't provide. This link to the application does.