Moving gantry Z axis

[A_Camera]

Jazz, those are very nice machines, especially the blue one.

You are right about the benefits, but I was thinking about moving gantry type machines, which are more popular and common among DIY builds. The ones you are showing are moving table type, and no doubt that moving the whole beam up and down, instead of just the spindle, would have a rigidity benefit there, as well as it can be made with more throat (Z to table) clearance also, without losing rigidity. For my moving table type of DIY machine, I also considered this type of solution, but then in the end, abandoned the idea for some reason, probably because it was my first build and was not that confident. Today I'd go for that solution, because for a moving table type of machine, it definitely is a good idea.

[JAZZCNC]

You are right about the benefits, but I was thinking about moving gantry type machines, which are more popular and common among DIY builds. The ones you are showing are moving table type, and no doubt that moving the whole beam up and down, instead of just the spindle, would have a rigidity benefit there, as well as it can be made with more throat (Z to table) clearance also, without losing rigidity.

Yes, those machines are both fixed gantry but the same can be done with a moving gantry machine and still have all the benefits be it slightly less ridged than a fixed gantry, however, still significantly stiffer than a typical Z-axis at full extension if say had a 300mm + z-travel.
This type of lifting gantry setup is common on very large industrial machines, although they often have a short Z-axis as well due to the size and weight of the lifting gantry.