Looking around at some of the smaller milling machines and smaller VMC's say (24"x18" or less XY) it seems like most are built on a bed mill design.

Is there some design reason for this? Are they more rigid than the gantry type? Do they allow higher speeds or something? Are they just less complicated to build?

I notice that once the work area gets much larger you see more Gantry or Bridge type mills.

Just looking for others thought and opinions. I have read thru many posts on here where people like certain designs or others, but more curious about the engineering side of things.

In my thinking, and I could be way off here, I would think a fixed gantry would most often be the best for rigidity rather than have a long cantilever head hanging off a column. Of course, the fixed gantry type also seem to take more room than the column types, but it is not like most of the small VMC's have a small footprint for their work area.

Is it just a materials cost reason why there are so many bed type smaller mills? Are the smaller bed mills actually more rigid than the gantry types? I can see where a moving gantry might slow down the speed they can be moved with moving the large weight around, but I would think a fixed gantry would have the least amount of weight being moved around and possibly be even more rigid and possibly more very fast. I know you see more of them when you get into the high precision chip manufacturing machines and all, which of course are not milling machines and don't have anywhere the loads on them.

Any thoughts would be appreciated. Not looking to start a flame war or anything. Just looking for some technical information from the folks experienced in machine design or use.

Thanks,
Chris

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