Thor, or should that be Zeus?

[Robin Hewitt]

Theoretically the bearing blocks should be bolted to the gantry and the rails to the bottom of the bed. If you put the blocks on the bed you introduce unnecessary overhangs and add a lot of metal supporting rails that does nothing. It should be more A frame and less triangular. OTOH, what do I know? -freaking smileys don't work-

[Chaz]

Theoretically the bearing blocks should be bolted to the gantry and the rails to the bottom of the bed. If you put the blocks on the bed you introduce unnecessary overhangs and add a lot of metal supporting rails that does nothing. It should be more A frame and less triangular. OTOH, what do I know? -freaking smileys don't work-

Thanks. Point taken. This was pointed out too (off this thread) in the design. Ill make the changes.

[routercnc]

Wow Chaz - excellent thread. Great to see someone putting a bit of thought in and going for it!

I would lean towards Thor, the top design, although both would do well.

In my new mk4 design I had to go with moving gantry because I still need to cut large wooden sheets, but with your brief these designs are excellent.

If the granite epoxy is too difficult to make/cast then it looks like it could be done with say 150x50mm sections all welded together. Then backfilled with epoxy granite. Weld on some flat 10mm bar where each rail will go, get it skimmed flat, and there you are.

For the spindle I wonder if you could have a bolt-on high speed spindle for aluminium (router mode), then bolt on a heavily geared down spindle for steel (mill mode). Or have both in place so you can choose.

Good luck with however you choose to develop this - watching with interest.

[Chaz]

Wow Chaz - excellent thread. Great to see someone putting a bit of thought in and going for it!

I would lean towards Thor, the top design, although both would do well.

In my new mk4 design I had to go with moving gantry because I still need to cut large wooden sheets, but with your brief these designs are excellent.

If the granite epoxy is too difficult to make/cast then it looks like it could be done with say 150x50mm sections all welded together. Then backfilled with epoxy granite. Weld on some flat 10mm bar where each rail will go, get it skimmed flat, and there you are.

For the spindle I wonder if you could have a bolt-on high speed spindle for aluminium (router mode), then bolt on a heavily geared down spindle for steel (mill mode). Or have both in place so you can choose.

Good luck with however you choose to develop this - watching with interest.

Thanks. We have discussed a dual spindle setup. I might want to stick a grinding spindle in there too somehow :-)

I'm looking at rail options for the Z at present, I have some other options to consider although already spent a small fortune on the parts thus far. I will have leftovers, will likely be put into a DIY CNC Lathe.

[Chaz]

Theoretically the bearing blocks should be bolted to the gantry and the rails to the bottom of the bed. If you put the blocks on the bed you introduce unnecessary overhangs and add a lot of metal supporting rails that does nothing. It should be more A frame and less triangular. OTOH, what do I know? -freaking smileys don't work-

Just to confirm you are referring to swapping the rail and cart here on the Z Axis?

[Robin Hewitt]

Just to confirm you are referring to swapping the rail and cart here on the Z Axis?

I was actually referring to the X. At the bottom you have two linear rails bolted to an enormous structure, most of which is superfluous, you only really need the bit under the gantry.
If you fit the linear blocks to the bit under the gantry and the rails to the table then the support will always be under the tool.
You lose an unnecessary overhang.

[Chaz]

I was actually referring to the X. At the bottom you have two linear rails bolted to an enormous structure, most of which is superfluous, you only really need the bit under the gantry.
If you fit the linear blocks to the bit under the gantry and the rails to the table then the support will always be under the tool.
You lose an unnecessary overhang.

Ah, ok, understood.

I'm just trying to find the reference design / document that I used. I did note that this is not final but the shape (with more support) is basically a triangle.

I am however more than happy to make changes based on experience, one of the reasons why I have started this thread.

[Boyan Silyavski]

The way i see it, if you go with high speed spindle, fixed gantry would be better, if you go with servo motor and Bt30, the VMC shape will be better. So at the end there is not so much to consider which shape you go.

With that size bearings and rails length, overhang will be irrelevant. You could try to make it small, just for a designers satisfaction though, but its not necessary.

[Robin Hewitt]

I cannot claim any "experience" making super routers, but I have made a few tables and converted a couple of milling machines. But enough of the X, here are my thoughts on the Z.
With a knee mill you have 2 controls for the Z, you can lift the table of lower the quill. A round column mill is similarly adjustable. When you CNC it you probably motorise the quill and use the other, heavy duty adjustment, to optimise the quill travel and get maximum support on a job by job basis. You would be lost without this double control of the Z and yet nobody puts it in a home build.
I suggest you make the entire gantry moveable in the Z with some big bolts so you can lock it in the optimum position. I do have expertise in this because when the locking bolts went on my mill everything went to hell in a hand basket PDQ

[Davek0974]

That's quite a neat idea there Robin, have never seen that applied yet.

I guess it depends on the intended use of the monster mill, spindle power and speed could dictate smaller (<10mm) cutters which would then indicate that smaller workpieces would be used - no use tickling a 300kg lump with a 3mm end mill I think.

That being said, a dual position gantry maybe offering the tool a 0 - 150mm and 150 - 300mm range could be useful, would need an assisted method of raising/lowering the gantry though - two trapezoidal leadscrews might work along with some heavy clamping method when in position.