Have you ever tried to post a link to your content on Facebook only to realize that an image is missing or the description isn’t there?
Naturally, you go back to your edit your article and add the missing content. Then you head back to Facebook and try to post the link. What, Facebook still isn’t showing the new content? Why? It is caching the Open Graph data!
In my experience this process has updated the Open Graph cache on Facebook every time.
Disclaimer: this is not a documented process by Facebook.
Learn more at http://opengraphprotocol.org/