Steel Frame 8' x 5' CNC - Advice Sought

[Clive S]

Ok, here is my updated table design with the extra supports in place.

I personally would not put a rail all around the bottom and I would add triangulation in.

I would have it sitting on say six legs, that way it would be a lot easier to set up on an uneven floor. Also make it out of 4mm or 5mm box section then you will have enough thread depth for fixings.
.
It might be worth thinking about having heavier cross rails and ditching the centre supports to be able to use the underneath to store sheet materials. ..Clive

[BrentonSpear]

Hi Guys,

I was looking at using 50mm x 50mm x 4mm SHS steel tubing for the frame.

Silyavski, that is an interesting thought. I suppose I could do it in 100x100x4mm SHS. I will have to do the price calculations. I am planning to get all the pieces cut to the required lengths at the place I buy the steel so the size of the SHS is not really an issue.

Clive S, I had always planned to add feet to the frame.

Here is the updated design with the feet in place.



For the gantry I am going to look at how I get a ball screw between the rails of the Y axis.

I think I will put an I beam inside the RHS beam and then remove material to make a void. I have seen other person do this and it looks doable.

[BrentonSpear]

What sort of span will I get with a 100x100x4mm beam? Could I get the full 2500mm?

[BrentonSpear]

I have had a rethink on the steel size and now modelled it on 75x75x4mm SHS.

[Boyan Silyavski]

Add some more inner pieces for the worktop area and you have it nice and clean

[Clive S]

I have had a rethink on the steel size and now modelled it on 75x75x4mm SHS.

That is much better now with the triangulation bits put in and heavier steel section. Good luck with the build. ..Clive

[BrentonSpear]

I have been thinking about having the bed raised above the rails to make it easier to get materials on and off the machine as suggested by another person.

If I was to leave the design as it is, is it acceptable to have a lighter steel (say 25x25x3mm) frame inside the outer rails to raise the bed above the rails?

Obviously I would have to increase the height of the gantry to allow this and I would also lower the rails from the 80mm height they are at now to more like 20mm.

Thoughts?

[Boyan Silyavski]

No. Either do it like it is or redesign it completely for the other type of machine, where the bed is raised.

There is a reason most strong DIY builds use raised sides on the bed and the bed is bellow.

For a first build is not advisable to make the bed raised cause most possibly you will finish with a machine having a weak link somewhere at the gantry. Not that is not doable, just needs some careful considerations.

If you look at forums you will see all machines of these type are weak or crappy, even if they have ton of steel in it. Especially this is the case if you want to do aluminum.

Not to speak of the difficulties you wil encounter of aligning properly the long rails