looking for a good 3d printer

[Zeeflyboy]

The point is that while it will work, a router just makes a poor 3D printer compared to something that is designed with 3d printing in mind.

If its all you can do for space/cost/trying out the idea/whatever then fine, as mentioned it will function but an ultimaker or something will run rings around any router conversion in actual day to day usability, productivity and reliability long term.

The reason why I say light is because it's much easier to build something that is fast and can run for hours on end efficiently if it is light. Note that light does not mean flimsy - a rigid printer is a good printer, but it just doesn't need the same bulk as a router, but needs to run for many hours on end with a lot of fast movements... personally I'd much rather have a light machine with belts vs a heavy machine with screws doing that, both for my sanity from noise and from a wear/tear and energy efficiency stand point.

As for leaving it printing, sometimes you have no choice. I've had 20hr+ print jobs and there really is no viable way of pausing in the middle. I personally set my printer up with a monitoring webcam and a smoke alarm tied to a smart power socket that will shut down the power if the smoke alarm goes off, but I've been printing for many years without any safety issues - there are several failsafes built into the printers themselves to prevent thermal runaways etc so they can be relatively safe left to their own devices.