Torsion box ( long winded)

So living in south Louisiana the humidity is high and we get a lot of temperature variations right now it’s about 50f and Christmas Day will be 81f my s house is made of wood and built on piers
Due to this my house moves a lot alway adjusting doors to fit the doorway and such ( it’s just Louisiana life)
I have my shapeoko on a metal table thats just a little short on the depth so the front feet hang a little over the edge, to combat this I have it sat on two 4”x4”’s front to back but nothing side to side
Need advice from all the experts in here !
If I built a torsion box just a little bigger than the foot print of my XXL would this help with flatness of my spoilboard, I can surface my spoil board and it’s nice and flat but a week later it’s not so flat due to the elements
Now being level will never work as I can level everything and as the temps get higher it’s not so level so was thinking metal table with a torsion box would help a lot for flatness
Just need a semi quick fix until I can pour a slab and built a shed just for the machine and table saws
Louisiana is not nice to square and level

Any help material wise and depth of said box would be welcomed, I’m sure I would have to use a good sealer on it so the humidity does not affect the box too
Thanks in advance

Here is a plan for a torsion box for a Shapeoko XXL. You could modify the dimensions for any machine you want. In the plan I give you several alternatives for making jigs to make the torsion box. Additional to the torsion box I have an XXL and it sags in the middle if you do not put a block or something. So I removed my leveling feet and put a piece of 3/4" rigid foam board down underneath the machine so the entire base rests on the foam. This foam gives support to the frame and helps dampen vibration and noise. Now there is not much noise reduction but every little bit helps.
torsion_box.pdf (2.0 MB)

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I appreciate the pdf sir

One question
I have seen others use the foam my concern is I’m pretty heavy handed so would like to hear about how well the foam hold up to abuse
Recently I have been using the painters tape and ca glue, as I’m heavy handed I tend to push down pretty hard until it’s glued would that not push my machine further into the foam, I know it’s a lot of surface area but still a concern
Also I’m thinking of using MDF 3/4 for the skins and 2x4’s for the frame and ribs
Then sealing !! I have made some things out of MDF and they just keep sucking on the paint or sealer, maybe plywood would be the way to go or maybe cover the torsion box with Formica ??
My trouble is I tend to over think and over engineer what I need to do

Also what rigid foam did you use there seems to be tons of choices out there

I cut the foam so it is just under the 4 corners of my xxl. The frame of the xxl distributes the weight over the foam and as far as I can tell the foam is intact after a year plus.

I use the tape and superglue but after I put down the first layer and superglue and put the second layer on the project as I lay the two together I use a J roller to smooth out glue and get a good bond with no high spots. Using your hands to smooth out can lead to uneven adhesion of glue and uneven surface.

J roller makes sense, wife has one for her cricut, it’s about to go missing lol

Sorry I thought you cut the foam to the machines dimensions and just took the feed off and layers it o too if the foam

To be clear the foam was cut to the same dimension as the foot print of the xxl. The torsion box has about 6-8 inches at the front with no foam and gives me a place to put tools etc.

Gotcha I will be doing that cause during tool changes my bits fall to the floor if I’m not careful
Will also add a little foam there just for this reason

Appreciate the help Gdon

I found a plastic box at dollar store about 12"x 2.5"x2" I put under router at front to catch router bits. Likely was a silverware box for drawer.

I searched rigid foam on here and seen a lot of your post sir
But still have the question
Although I have not measured for sag in the middle of the machine, surely it can only sag so much then if you add your waste board and surface it the machine should be good as long as the new waste board does not pull the sag out when you screw it on,
So the sag is on the y or x axis or both ? I’m thinking both
Would I not be better adding my torsion box then taking the MDF off my machine and adding a cross that would cover the z, y axis underneath the metal framing and cutting the cross to suit my measurement height wise, or would just a length of 2x4 but to the height needed across the x axis
I can’t see the machine saying in the y axis if this is done ?
Told you I over think things

You did not say what machine you have. The xxl is subject to sagging in the middle. There is a steel beam in the center that runs fron side to side. The leveling feet are only in the corners and the center is unsupported. You can put a block in the center but the foam gives support to the whole base of a Shapeoko xxl. The torsion box makes a stable platform for the machine by giving a sag proof solution and the foam helps asorb vibration and the torsion box adds mass. Many people have xxl"s with just a plywood base that works well if you support the center beam.

The torsion box is great but not absolutely necessary if you have a solid base for the xxl to sit on. All cnc machines benefit from a solid base. There is a lot of momentum and vibration caused by the router and sudden direction changes on a cnc. The larger the cnc the more movement created.

I have the shapeoko 3xxl
Going to build the torsion box and try the foam method, nothing to learn if the foam does not work but it seems a few people swear by it
Appreciate all the input sir

Another quick question
It is overkill but

Would y’all recommend once the torsion box is complete to drill a hole in each box section and fill with expanding foam ??

Just a thought

I dont think that would add much. It would not add to mass. Sound dampening maybe but ridgid foam under Shapeoko would likely do more. If you use foam use minimal expanding. Expanding foam may explode your torsion box.

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