I saw this printer mentioned on a facebook forum & seems like this method having the build plate stationary is a better idea than having the build plate moving at all which is what the delta printers do also. Not sure if this is a decent printer or not, but I liked the idea. Are there other core xy printers using this movement method? Seems like all the ones I see have the build plate moving up & down.
Funny enough, I was wondering this same thing and a web search brought me back here.
It looks like it is very doable, but the engineering tradeoffs make it so that raising and lowering the bed on the Z axis like the Ultimaker or the MP3DP Repeat are easier overall, unless there is some compelling reason to want a fixed bed. It would appear nobody has such a compelling reason, and so the fixed-Z approach is uncommon as a result. (Not counting delta printers.)
That gecko printer looks interesting. You might need a counterweight to prevent the Z axis from falling when the Z motor is not powered.
The two benefits to a moving XY gantry are that it allows large-envelope printers to have mains powered beds and for 80%+ of all printing time it puts the reciprocating masses of the printer very low to the ground (rather than wobbling around at the very top of the frame).
I don’t currently think the benefits outweigh the cost. Even if the XY motion is lighter than your build plate the build plate is mostly just an inert mass that can be raised and lowered. The CoreXY motion on the other hand has constant lateral action/reaction going on all the time and making sure your Z motion is also providing zero backlash vs. lateral loads is a bit of a taller order than just having to hold the build plate still and let it down gently.
One idea I’ve kicked around now and again is a sort of ‘drop-table’ CoreXY design. The XY motion is bolted to a table/desk/box/shelf/etc. and the Z motion hangs underneath the motion and allows for the build plate to descend.