Your "vote" is one of the key things. As Jon Ericson pointed out to Mechanics.SE before we graduated and were asking the same question asked here, he stated:
... voting is the engine that drives the reputation economy.
I think Mech had a little different scenario than does 3D Printing, but it still holds true. If you want people to show up and do things, you (and everyone else) needs to vote. Up, down, sideways ... doesn't matter. They all help drive people to do things in every Stack.
Looking at the above link, you can see one of the things which is important to graduation is having the right user base. You have to have people who have the ability to do things which only those who have met the point level can do. As it stands the highest ranked person by point total is Tom van der Zanden. He hasn't (as of this writing) broached 10k points. There are two users who have more than 5k points, and another five who are over 2500. How do you improve this scenario? You guessed it, by voting.
I realize with sub two questions per day (QPD), there's not a lot to vote on. That can be overcome as well. Those of you who have had issues or have met challenges have knowledge. Write down those challenges you've faced in a question. Then, either write an answer for them, or let someone else figure them out. Either way, you are creating opportunity for the site to expand. That opportunity will be giving someone a chance to vote and/or answer the question. Plus, you are doing what SE wants done in the first place: bringing and recording knowledge. It's a win-win.
There's a ton of other things which can be done to get 3D Printing graduated. I'm sure we'll get there sooner or later. I hope I can help in some small way. I'm not the bastion of all knowledge to get a site graduated, that's for sure, but having gone through it with Mechanics gives me some insight.
Here's to the future and what it will bring.