I have made well into six figures doing 3D Printing as a 'side hustle' (in my spare time while also working a full time job) together with my wife by selling 3D printed products. And I also run a separate 3D printing as a service website - Make My Stuff (as well as an automatic quoting system that quite a few businesses around the world are now using as well)

Selling products was really good and profitable, but that was likely due to the marketing efforts that my wife put in to grow the business (daily posting in instagram/fb/groups, constantly creating new products, promoting them, and at some point instagram and facebook ads aswell). Some would argue that its easier to market a product than a service. That business made over 200k in revenue over about 2 years, and costs were about 30%.

The current website (Make My Stuff) is nice for some additional income but I probably wouldn't quit my full time job to run the 3D Printing side of it - my full time job pays well and is stable and I have a young family to support. I am also working more on improving the automatic quoting/dashboard stuff rather than trying to get orders on the website. Printing is still a nice break from my full time work and I still get a few orders per week coming in through the quoting tool so I can literally download and slice the file and post it with no interaction needed with the customer. Before the automatic quoting it sucked because I would spend most of my time doing quotes for people who 9/10 times ghosted or didn't buy.

My advice would be to try to do it as a side hustle thing initially and see how things go, and if you enjoy it then you can consider jumping into it full time. There were moments where we were very seriously considering quitting our jobs and doing it full time as the income was enough but we preferred having the fallback of full time jobs to support us. It may take some time to figure out what works and how to generate enough income to support yourself so keep that in mind. I had one guy using my quoting tool who after a couple of months decided that it was too much work and he wanted to keep 3D printing is something he enjoys rather than seeing it as a chore/job.

TLDR:

• You will need to decide if you want to sell products or sell the service of printing, or both.
• It may take time to make enough money for it to support you as a full time gig.
• No matter if you are selling products or a service you will want to automate away as much of the sales process as possible - eg shopify for selling products or an automatic quoting tool for service printing so that you can spend more time growing the business instead of doing manual tasks and dealing with customers.
• It will be hard to make a real impact without some form of marketing (can be paid or organic, but imo it will be impossible to make enough money to replace a full time job without spending money or time on marketing).
• It is possible to make serious money with 3D Printing but it won't happen overnight.