Steel Frame 8' x 5' CNC - Advice Sought

[BrentonSpear]

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

[Boyan Silyavski]

Hi,
when i said above for the plates i meant the gantry.

What would be the square steel box profile size? I calculated it many times and for steel machine/this size especially/ is best to use bigger profile 100x100x3 or 4mm and simplify the structure. I say always 100x100 as it is the max that could be handled and cut at home using dry saw or small band saw.
The benefits are:
-simpler
-easy to cut at home
-easier to solder
-stronger
-less metal for the same strength so cheaper

You could read more here and see changing the table design leads to substantial savings http://www.mycncuk.com/threads/5302-...highlight=tony

In fact if you have the means the bigger is better here.

[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?