Backstory: Recently I've been getting a few things custom 3d printed so much so that I have a cheap 3d printer at home to test out a few things. My printer is by no means high quality but it does the job of an acceptable prototype of simple objects. Printing anything complex, the result just falls apart (literally).
The Idea: A marketplace to get instant quotes on 3d models.
Deep Dive: The key with this one is to give the end users a really simple and intuitive interface to get quotes instantly. Users would be able to upload their 3d file, the volume would be calculated and then they could select quality (microns), material, color(s), quantity and shipping distance to get an instant/reliable quote.
On the backend, you would have to build an interface for 3d print studios to define the above features. The "special sauce" here is with all this detailed information, the end user doesn't have to manually call vendors to get quotes which can take hours.
Validation: I've manually called 3 vendors for quotes and information and it's exhausting. 3d printing is still a new field so the variance in vendors is high.
Monetization: You would take a percentage of every order as a fee. This scales with the business as the platform processes more money, you'll make more in fees.
P.S. This is similar to another idea I've posted before. The focus here is on the end user experience for getting instant quotes. I feel this niche is going to get bigger as technology improves, some of the models printed from a form2 are really impressive.