This question was too long for the search function. Is there any consensus on which is the best system. Fixed gantry with a moving table or fixed table with a moving gantry?? Any info appreciated.
In my opinion, a fixed table with a moving gantry due to versatility. For example, with tiling you can cut things much longer than the machine. It would be hard to fasten down an 8 foot (for an extreme example) long sheet of wood to a moving bed.
Finding consensus in this hobby is about as likely as hens teeth I'd agree with the others so far though, and add that if your workpiece was, for example, a heavy slab of timber, moving the gantry is likely to give less problems. Alex.
Technically you should get the best precision stack from a moving table. The fewer stacked axes there are in any given chain, the better. That isn't necessarily always workable in practice, though. Moving table means you need twice the width or depth for your machine to move, and if you have 800-1500mm axes, that's a LOT of extra space. Available power and budget for motors and drivers also plays into it. It's easier to skimp on motors and just drive a gantry than it might be to start trying to throw around a hundred pounds of timber, and that's before you get into momentum, acceleration, and support for the machine itself. Really depends on what you're doing and why.
Screw drives are best for machines that cut materials and belt drives are OK for 3D printers and lasers.
I'm going to shoot down every answer so far, aside from Rob's. What's the best color? What's the best animal? What's the best car? There is no one answer. It all depends on your actual needs. Note that I said actual needs and not wants/desires. If you have a machine that will be milling super hard materials, you'll more than likely be using a moving table mill. If you are cutting woods, foams, plastics, and other not so hard materials, then a larger table to accommodate the larger stock size is needed. Moving a larger bed becomes impractical which means that you are now moving the gantry. Another factor is that harder materials, with the exception of sheet goods, are usually much smaller. You build large cabinets out of "soft" wood, but the small hinges are made from metal. This also applies to the linear motion setup. You need speed, go with belts. You need strength/rigidity, go with screws. The middle ground would be rack and pinion. TLDR: You don't wear your 5 year old daughter's playground shoes to work. Different machine styles serve different purposes.
Well, since the question was about consensus, can you really shoot down any answers? After all, everyone is equally right since it is just an opinion. That being said, it would be nice to have multiple machines. One for metal and one for larger projects. For me though, even when I cut metal the pieces start out large. Why? I buy aluminum by the pound and every cut costs $3 at the metal dealer. I look through the cut-offs and buy pieces that are large enough for my entire project so I do not need to waste money on cuts. $3 wasted could have got me another pound of aluminum. So, for my updates to my current CNC, a mini-mill or a c-beam would not work unless I had other tools to cut the pieces down to size which would then lead to more waste since my "nesting" of parts would be far less efficient. I 100% agree with you that the first question should be, "What do I plan to do with it." For me cutting large objects was important and I found the moving gantry was the best overall solution. It also cuts aluminum very well. Someday in the future I may try to build a smaller moving table design specifically for metals, but I think a plasma build would come first.
Well, to be fair, there's definitely consensus on what the best all-purpose 3-axis system is- moving XY table, C-column or gantry with Z axis, made from cast iron or mineral epoxy. That'll cut basically any material at high speed with high precision with little-to-no chatter. The problem is, "what is the best system" isn't the correct question, because there's a good chance it's either too big or too expensive. "What's the best system to cut ____ with a maximum power input of ______W that fits into an envelope of ___ by ___ by ___ ft and costs below my maximum budget of $_____?" is much closer to the correct question, but if someone understood sufficiently to ask the more precise question, they likely wouldn't need to ask it in the first place! A Haas VF2SS needs a minimum 240V 40A line and costs ~$60k. It won't fit under a garage door either. Great low-mid-price machine, and it'll cut the most incredible wooden coasters you've ever seen. But you still wouldn't buy it for that purpose!
