Advice on Mammoth CNC Router Build - Steel Framed - 2440mm x 1220mm cutting area!

[JAZZCNC]

I've used both methods in the past and each work good and each have there own +/-

Full Epoxy level is ok and works good but has you can see with clives pictures there's plenty of prepartion required and on large machine like what the OP wants this means a lot of work. This prep has to be very good and fully sealed other wise sag can happen and being 3mtr length the chances of this happening are plenty.
Yes it's not the end of the world and can be corrected if it happens but it's a ball ache when it happens.!! . . . . I'm sure Both clive and Jonathan will tell you when pouring and it starts leaking your running round like headless chicken trying to suppress it and again over 3mtr and between 80-100mm width that's a fair amount of epoxy your fighting with.! . . . . It's also not cheap.

Now with Epoxy putty feet and shims you don't have this problem has there's no liquid epoxy involved but you do still have to do careful measuring and setting up to get rails on same plane. Unlike The above epoxy method which takes care of this for you, thou if it's not perfect which you won't really findout until machine is built and working then it's a lot more work to correct.
The epoxy shimming is very easy to correct on the fly and while machine complete and working. You don't need to strip it down to correct.

Now to be honest I think the OP is correct to use Both methods has 3mtr is a long length of boxsection to ensure is straight and true, which it won't be, so would need some work even with Epoxy putty method and the Epoxy liquid method will make light work of this. The Epoxy putty and Shims will give him the fine tuning he will need over this length machine.!!

[Jonathan]

Looks ok... but probably a bit OTT. Don't leave the ends of the long pieces of box section cantilevered - support them with a piece at 45°.

I'm sure Both clive and Jonathan will tell you when pouring and it starts leaking your running round like headless chicken trying to suppress it

I've not had any leaks at all. The guiding aluminium strips were firmly bolted to the frame, and the wooden pieces used covered with grease, which makes a good seal, and clamped with plenty of G-clamps. If it had leaked then I would have addressed the situation in a calm manner, using the glue gun and tape I had on hand just in case. The running round can be left to the three birds in the garden...

[JAZZCNC]

I've not had any leaks at all. The guiding aluminium strips were firmly bolted to the frame, and the wooden pieces used covered with grease, which makes a good seal, and clamped with plenty of G-clamps. If it had leaked then I would have addressed the situation in a calm manner, using the glue gun and tape I had on hand just in case. The running round can be left to the three birds in the garden...

Oh I'm sure I'd read somewhere you had a Leak.??. . but obviously not so I stand corrected you obviously don't know.!! . . .But I assure you that you would run around trying to stop a leak if it happened no matter how COOL . . . . . you think you are.!!

[Wejjmeister]

First stage of the MkII done, Im still working on it so bear with me. I decided just to use the epoxy on the tops of the rails as plates and shims plus epoxy will be a mare. It may be slightly better but I dont intend on moving it once set up so I think Epoxy should suffice.

The whole of the frame will be sand filled too, so not worried about resonance.

Next step is the rails and ballscrews and placements of. Will add more a little later hopefully, time permitting!

Thanks ever so much for all of the comments though guys, a real help!

[Boyan Silyavski]

The diagonals at the sides, it seems to me help nothing except add weight. Should work fine without them, but that's me :-)

[EddyCurrent]

The diagonals at the sides, it seems to me help nothing except add weight. Should work fine without them, but that's me :-)

Even if there was 3 each side, one at each end and one in the middle, or even 2 each side, one at each end, that would be enough.

[Wejjmeister]

Even if there was 3 each side, one at each end and one in the middle, or even 2 each side, one at each end, that would be enough.

Should I remove these then? Im all for saving material, especially considering the prices of steel these days!

[ba99297]

Sorry for interrupting but I have an idea
Could it be possible to combine both methods (epoxy and shims) BUT instead of epoxy use clear coat for car painting. The clear coat will be the mean to show us which is the true level between the rails, so then we put shims and putty and fit the rails on that level. For that size of machine that may be 2-3 kgr of epoxy will be needed, the difference to the final cost will be significant After the putty pures we could even took off the clear coat as I don’t know how strong it is in getting pressure from the rails. In that way we don’t pay too much money for the epoxy as I think clear coat is much cheaper and we won’t waste too much time to true level the rails as we use the clear coat as guide. Regards the pure time of clear coat we could use a catalyst that will make pure time longer.
Also instead of clear coat we could use anything chaper that has self leveling properties
Just an idea I don’t know if it is correct

Vagelis

[EddyCurrent]

Also instead of clear coat we could use anything chaper that has self leveling properties

water ?

But the idea with epoxy is that it finds it's own level then hardens to that level and job done, with the method you suggest how would you measure the depth of clear coat (water) to know that the frame underneath was level ?

[ba99297]

water ?

But the idea with epoxy is that it finds it's own level then hardens to that level and job done, with the method you suggest how would you measure the depth of clear coat (water) to know that the frame underneath was level ?

What i suggest isn’t so different with the epoxy method. Clear coat is also a resign but I think much more cheaper that will harden when it cures. Water isnt hard unless it becomes ice. Water could give us a perfect level but the question is how we could “capture” that level. What about self levelling floor resigns ?