A quick note on scaling up or down the Delta-Pi and Delta Steel designs

The Delta-Pi and Delta Steel are very much scalable designs - within reasonable margins and not as easily in all directions.

If you intend to print taller objects, you can just use longer pieces of square stainless steel tube (my Delta Steel prototype uses 800mm long columns, whereas the original Delta-Pi is specified for 670mm tall columns). Yes, you'll need longer GT2 belts, but that's not expensive. Within reason, the printer structure is strong enough to avoid any flexing that would significantly degrade the quality of the prints.

On the other hand, if you want to have a larger print area, you can just use a wider spacing between the columns, but that implies two things:

1. You'll need longer carbon fiber arms.
2. You'll need a larger heatbed.

Now, longer carbon fiber arms are easy to get, but larger heatbeds... well, that's different. I am using a standard MK2B PCB heatbed because these are very inexpensive (< €8) and the size (200x200mm) is quite enough, at least for this prototype. Also a 200x200mm piece of borosilicate glass is < €12, so again, not a fortune.

Going for a slightly larger round heatbed would practically double the cost of this subassembly, and a much larger heatbed of non-standard dimensions would require a custom machined aluminum plate and a heater of some sort, plus again a specially cut piece of glass, costing four times as much or more.

With the total cost of this prototype well under €300, I don't see myself spending nearly €100 just for a larger heatbed that I would use at most once or twice a year. I guess it all depends on your budget!