I am about to construct a torsion box tabletop from MDF, and am wondering whether it would reduce the rigidity to cut openings on the sides, braces, and maybe even the bottom to reduce the weight.
There are many videos on yourtube about construction of a torsion box. I have seen many with the skeletonized sides. The strength of a torsioin box is the amount of surface tension created by all of the interlocking pieces on the top and bottom skin.
I am about to build one as well. Mine will not have any skeletonized side panels but that is because I will not be using the inside space for storage. I just dont want to take the extra time to cut the holes. For me the extra time is not worth the effort for a limited return. If you however want to cut the holes and use them for something it will not hurt strength but I would not make the holes on all 4 sides. Maybe the two short sides if your table top is not square. MDF is pretty strong but it is weak when cut into thin strips. If you were to put a 4x8 sheet up so 4 feet were sticking out you could break it in half with considerable effort. But if you were to cut your MDF down to 6 inches by 8 feet and stuck 4 foot out you could easily break the MDF. So in my mind the bigger the piece of MDF the stronger it is.
Not sure you would get that much weight reduction. If you have a support structure under the torsion box that cannot hold 2 sheets of MDF you probably need to build a stronger sub structure. As I stated earlier the outside cutout might be ok but I will not be making any cuts on the internal grid to reduct weight. MDF is not that structurally stable because it is sawdust and glue. If your internal grid were solid wood that would be stronger but I would not skeletonize solid wood either.
If you search for “torsion” you’ll find the one below and several others.
https://community.carbide3d.com/t/torsion-box-table-top-for-xxl/30374/12
That’s what my question was based on. I have seen a few with openings on the sides, but I am also wondering about doing the same to the interior bracing. I would feel comfortable doing this to plywood, but I have not used a lot of MDF.
I’ve seen skeletonized torsion boxes for only two reasons:
- To reduce the overall weight of the box - which for a stationary, vibration-dampening platform, I don’t see that you’d need / want to reduce the weight.
- To allow for downdraft suction / vacuuming - which might actually be an interesting addition to a CNC solution. I could see putting holes into the spoilboard and attaching your vacuum to that - pulling the dust down through the table and routing the air out through the skeleton. Interesting if you’re in an enclosure?
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It’s also useful on the Paulk table for storage.
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… or when building it in a place other than your shop, and you have to move it across town with minimal assistance…
@clintonmagus So that’s an interesting trade off. For me, the heavier the base, the better - unscientifically, it feels better and seems to dampen vibrations better…and unscientifically, seems to reduce the noise.
If I had to move it across town, or ship it (and pay), or make it mobile - then yes, it would be a tradeoff that would require some consideration. It might be worth the additional resources to lug a heavy base, if it’s a one-time occurance.
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