A new hope: Epoxy granite and steel.

[JAZZCNC]

I cannot build a fixed gantry, there is no way for me to mount the workpiece vertically if I went with a moving table. There would be no point in building any cnc if I can't mill all 6 sides of the work piece.

I have looked over hundreds of designs over the past half a year and only a moving gantry with a fixed bed with a cutout ala Datron allows me to mount the workpiece in all orientations.

Only a 5 Axis machine can allow you to cut on all 6 sides in one operation. If your meaning to re-fixture and cut the other 2 sides then that's easily fixed, it's called an Angle plate bolted to the bed. Because that's all the Datron is providing with it's cut out, it's just an inverted angle plate built onto the end of the bed.

Other than that there is no difference between Fixed or Moving gantry other than Strength and size, Both have their own strengths and weakness but in your working envelope then the Fixed gantry wins hands down if you are wanting a strong machine.

If you want to work on 5 sides in one operation then Bolt a 4th axis to the table, again this would work on both designs but the Fixed gantry will do it better because it's stronger.

The spindle choice is pretty easy though. One day your bank account is full, the next day it's empty. If I went with a motorized spindle, I'd be screwed if either of the components broke. Cartridge + motor is far safer if something were to brake and needs replacing.

I'm happy to be proved wrong though.

I wasn't meaning the choice of separate Spindle + motor, that works good, but more your implementation of it is too complicated. Also, the Z-axis design is narrow and weak which will make all the trouble you'll be going to a pointless exercise.
There are plenty of examples of ATC spindle setups, just about every Milling machine with ATC uses the same setup. You just need the same setup and just rotate it 90deg so it's at the side if you don't have the room behind the spindle.

Also, I'm not sure your choice of Servo motor is correct as it looks just like an axis Servo rather than a Servo spindle motor.?

These are just some of the things I'm meaning when I say you are going to waste lots of Euros because none of them is cheap and easily done wrong if you haven't thought about and planned every last detail.

Theory and Cad are great, however, Reality is a Mother - F@~ing -Bitch just waiting to slap your face and kick you in the Nuts who never plays by theory's rules and changes them to suit Her whenever she wants.

[jarjar]

If your meaning to re-fixture and cut the other 2 sides then that's easily fixed, it's called an Angle plate bolted to the bed. Because that's all the Datron is providing with it's cut out, it's just an inverted angle plate built onto the end of the bed.

I can see how this would be problematic if you want to mill on the side of long pieces that won't fit under the gantry. With a fixed bed the cutout allows the work piece to extend below the bed. If OP wants to do a lot of those pieces then the moving gantry seems indeed the way to go.

About the sawn surface to bolt the spindle on, I think this is a big no-no. I'm not talking about precision watch making, just basic good practice for mating surfaces. If the contact area is bad, you will lose most of the stiffness and also distort the spindle housing, possibly damaging the bearings very quickly.

[JAZZCNC]

I can see how this would be problematic if you want to mill on the side of long pieces that won't fit under the gantry. With a fixed bed the cutout allows the work piece to extend below the bed. If OP wants to do a lot of those pieces then the moving gantry seems indeed the way to go.

Pro's and cons to both but IMO the cons for having the slightly longer length end machining the price is a too high price to pay in strength terms. There are other better ways. . . For instance.!

For high clearance requirements, I have a design that will work and provide high clearance under the gantry with minimal loss in strength. I've just built a small version with a cutting area of 500 x 500 x 350 that could easily have the clearance and strength increased if required without any impact to it's cutting ability.

[hardenum]

the Z-axis design is narrow and weak which will make all the trouble you'll be going to a pointless exercise.

I thought it's pretty strong, stronger then what I'd get with a U plate and a spindle bolted to it. I based it on dmu 340. In which direction is it weak?

I can see how this would be problematic if you want to mill on the side of long pieces that won't fit under the gantry. With a fixed bed the cutout allows the work piece to extend below the bed. If OP wants to do a lot of those pieces then the moving gantry seems indeed the way to go.

That is what I meant.