I have a printer that started life as an Ender 5 Plus. the print volume is 350x350x400. I have printed some pretty big things, like a full size Mandalorian helmet in one piece, and never maxed it out. A lot of my prints would fit in a Bambu lab A1 mini. Ask yourself how many large prints you’d do in one piece. Also, printing large prints can be stressful, as failures mid print are a lot more painful in large prints. You won’t see many printers larger than 350 for a reason.

My printer has been converted to an Endorphin Hybrid CoreXY so of the original printer, little more than the frame, motors, and bed remains. It’s a pretty competent printer. Over 3x the stock speed, good quality prints, and cost me around 150€, including an overkill (not really, has room for a toolchanger mod I’m planning) Octopus Max board. if you use a simpler board, you could probably shave around 40€. I had the printer, so it was a no brainer for me.

I got a couple of rails that were larger, because for some reason they were cheaper than the original. I cut them to size with an angle grinder on a miter adaptor which I had, but which are cheap. Just make sure you wrap the rails in masking tape, and grind down the edges a little. Any speck of iron dust will wreck the carriages.

Ender 5 Pluses are cheap used.

If I were starting from zero, maybe I would have looked into an Elegoo Centauri carbon, 310€, or an Anycubic Kobra X,339€ including 4 color MMU, or ideally a Snapmaker U1 toolchanger, 850€.

Just because I have some rails wouldn’ really justify building a printer from scratch, but that’s just me. To me is like justifying building a mountain bike from scratch because I got some wheels free.