You are touching 2 different topics with your question.
a) Which is the appropriate license for hardware?
b) How to prevent that someone else can get a patent for your device?
For a) you might want to study this Wikipedia page. For your purposes you might want to start with a look at the TAPR Open Hardware License. I believe that it is much better than the CC licenses for hardware because it was tailored for it and understands the difference between a description and the object made based on the description.
For b) you need to look at the concept of Defensive Publishing. Nothing ever will be able to prevent that someone files a Patent Application for a specific idea. But with a clear and specific description of your device, the advantages, the rationale behind design choices, etc. you will be able to create Prior Art which can prevent that the patent application will be allowed and that a patent will be granted. You could use the project documentation that comes with the 3D printable files for defensive publication purposes, or you could write a separate file / description, and for this description a CC license, e.g. CC BY-SA, would be appropriate. For more information about Defensive Publishing you might want to go to Patents SE, for example here.