Any public disclosure anywhere in the world forms part of the prior art. Dates are hard to establish for webpages and so they're not generally a good form of disclosure - "defensive publication" is the term if anyone wants to find more info.
>"the patent office is guaranteed to look at the sources on that list"
The PCT minimum documentation is what must be available. The examiner will have to balance time and costs (databases of journals can be costly to interrogate) against their considerations of what material it would be useful to search.
In the UK the examiners used to keep up with journals appropriate to their field - so publishing an article in a trade journal or maker magazine about 3D printing would be a reasonable place for disclosure in this case.
There's another option for those familiar with the patent system - pick a country with low fees and file an application, get an A-publication and abandon the application. In the UK that will cost £30 (~$50) on application plus £150 for the search (you can file both online and get £30 off). It doesn't matter how big your application is; you don't get charged more for a 1000 page application than you do for a single page. It won't get refused until after publication even if it's absolute nonsense. It can however take a couple of years but you can reduce that to about 5 months by getting an accelerated search.
Aside: Theoretically you could break the UKIPO by submitting an application that's millions of pages long. Under R48(1) the UK office has to provide copies to anyone on request for a fee of £5 (with a Form23). There doesn't appear to be a restriction on the address either, anywhere in the European Economic Area is fine. However there's also a rule that requires one to provide, or pay, for 3 paper copies of an application to be made IIRC.