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

**Wejjmeister** · 05-01-2014

Thanks for the comments. I have made a few adjustments to the design based on comments made and also my own thoughts (dangerous!)

I have added a second 3m length of 100mm x 100mm box along the top, this gives me around 200mm on the Z axis. The plate of Aluminium on the bed will be 20mm thick and surfaced flat. I will set the rails along the 3m steels on Epoxy as in Jonathan's build so they are as true as possible, and the Bed will also be supported with uprights rather than diagonals, purely because the frame must bolt together and it is easier with uprights than diagonals to do so, without hopefully compromising the overall strength, I can add feet below the uprights if you deem it sensible too?

Let me know your thoughts guys as I would like to start on the frame soon. Ignore the frame for the Z at the moment, its in its very very early sketchup stages and will change A LOT from now...

Thanks in advance!

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**JAZZCNC** · 05-01-2014

I wouldn't use that method to build it.? I would drop the extra top rail and just extend the uprights to get your extra height.
It will save on material and resonance because those will be 2 large drums you'll be creating. To be honest I wouldn't use 100mm Box I'd go with 80mm and thick walled.
I'd use the design Eddy showed with top rails sat on plates which can be adjusted into plane much easier. The work involved with Epoxy is quite involved and to be honest a complete waste of effort if your going to use those Cheap round rails has there will be more error in there base than the surface your fastening to.! . . . . I also doubt you'll get it any better with epoxy than using the above method and it will take much longer and not be has flexible, it will also cost lot more money.

Show us the same picture but with out the bed base so can see the bracing etc.

**Boyan Silyavski** · 06-01-2014

On your last picture it seems you were thinking mainly of cutting aluminum

. If you continue with this design, take care that the rails on the gantry should be maximum low, near towards the table and as round rails don't like that position nor milling aluminum something has to change there, for starters -square rails.

**Wejjmeister** · 07-01-2014

Originally Posted by silyavski

On your last picture it seems you were thinking mainly of cutting aluminum

. If you continue with this design, take care that the rails on the gantry should be maximum low, near towards the table and as round rails don't like that position nor milling aluminum something has to change there, for starters -square rails.

Would it be better to place the rails (HiWins) on the underside of the gantry then? I can incorporate this into my changes too if so? The issue then will be travel...hmm!!

**Lee Roberts** · 07-01-2014

Originally Posted by Wejjmeister

Would it be better to place the rails (HiWins) on the underside of the gantry then? I can incorporate this into my changes too if so? The issue then will be travel...hmm!!

Hi Wejjmeister,

The ideal rail arrangement for these types of rail (supported round) is like what you see in the first pic below on the Y Axis (machine bed), so what your looking for is the base/bottom face of each rail to be facing each other. This dose make it harder when you come to true the rails to each other and get them on the same plane's but it is feasible.

This is true for any axis you use this type of rail for, so if you look at pic two below i'm selected in green the faces I think you should use to mount your rails. If you mount them on those faces, the other nock on effect is that you are also bringing the gantry closer to the bed.

.Me

**Jonathan** · 07-01-2014

Originally Posted by Lee Roberts

The ideal rail arrangement for these types of rail (supported round) is like what you see in the first pic below on the Y Axis (machine bed), so what your looking for is the base/bottom face of each rail to be facing each other.

Except, as specified in post #8, he's not using supported round rails. Most Hiwin (or similar) type rails have equal load ratings in both directions, so just mount them in the way you think is easiest. How they are orientated in the current drawing is not a bad idea as you can use epoxy to level all the surfaces, but there are some disadvantages.

**Lee Roberts** · 07-01-2014

Originally Posted by Jonathan

Except, as specified in post #8, he's not using supported round rails. Most Hiwin (or similar) type rails have equal load ratings in both directions, so just mount them in the way you think is easiest. How they are orientated in the current drawing is not a bad idea as you can use epoxy to level all the surfaces, but there are some disadvantages.

Bugger missed that post, o well its their for everyone else then lol, thanks Jonathan.

So, are you going to go as far as epoxy Wejj or just shim the rails when the time comes?

.Me