Hybrid gantry

[Lee Roberts]

Humm, not much i can added really. When i designed my machine i gave myself enough "room" to work with material of a max hight of around 100mm with about 70-80mm travel on the Z, the machine was designed for working with thin sheet materials.

I thought that i should pay attention to keeping the X axis center as close to where the cutting action was taking place as i could, as was the same for the other two axis's, i've seen a number of diy machines where they seem to have made the z axis longer/higher/taller (whatever) than would ever really be needed, some having 200mm + travel and then dumped it on an x axis so far away from the Y that i really couldnt understand the point of having such a tall Z?

I dont know, but i was under the impression that we should be trying to keep the cutter as close to all axis center's as we can, Dean ?

.Me

[Jonathan]

i've seen a number of diy machines where they seem to have made the z axis longer/higher/taller (whatever) than would ever really be needed, some having 200mm + travel and then dumped it on an x axis so far away from the Y that i really couldnt understand the point of having such a tall Z?

My Z-axis is 400mm...I've not got anywhere near to using the full travel yet, but it doesn't hurt to have it since I have the adjustable height bed. The reason I made it with so much travel is to give room for 5-axis (XYZAC) machining which shouldn't be too far away.

[JAZZCNC]

I dont know, but i was under the impression that we should be trying to keep the cutter as close to all axis center's as we can, Dean ?

.Me

This is were I think it can go wrong or be mis-understood.? It's 2 completely different issues or reasons.

The main reason for trying to keep all axis close to centres etc is more because of even weight distribution and loadings on bearings than for cutter performance.
High sides design is for strength and ridgity by not having flappy gantry sides so less resonance hence less chatter at the tool where it matters most, thou really to make best use of these high sides you should have an adujustable bed.

Regards long Z axis extensions well this is a personal choice and also dependent on machine use. Most of my machines never have more than 200mm Z extension unless special reason like foam block cutting. The main reason why I design and build machines with high sides/adjustable bed other than the said strength gains is for flexabilty.
As well has allowing a greater range range of materials sizes It allows the use of vices, 4th Axis, large Or odd material size or shapes, long drills or long cutters for materials like foam all without sacrificing strength or introducing to much flex and therefore chatter at the cutter.

The negatives which I persoanly find hard to find any are massively offset by the gains.!