I have installed a aux mdf wasteboard on my shapeoko 3 xxl, similar to all the others out there with t nuts on the bottom.After measuring I have a .003 sage in the center. I ran a flattening bit across all of it. Is this normal? Doesn’t seem like a lot to worry about but curious what other people have seen.
Yup. Sag is about what you would expect.
Ok so without putting a aluminum wasteboard in, that it normal?
It happens — it’s a large span. Folks address it in a lot of ways, the best option seems to be adding four leveling feet under the wasteboard.
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Are the feet put in the middle to support the span?
I put a shim under the middle of mine which helped but I find the mdf (even though sealed) changes with the humidity. I most often put another piece of 1/2" mdf appropriate to the size of my workpiece on top of the original and surface that with a surfacing bit making it true to the machine. This is especially critical when doing a v carve.
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Place them around the middle so as to sub-divide the span.
It could be a good idea to suggest in the instructions to new owners to drill and tap a hole in the middle plate under to install feet. It is much easier to do this when you first assemble the Shapeoko. Since it is a common issue, maybe that could be done at the factory as part of an upgrade to the Shapeoko… or not.
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Thanks guys I think I will try tapping a whole in the center for a leg.
I just took the leveling feet off, set it on a rubber mat, which is on a very sturdy bench, then shimmed anywhere the frame didn’t touch. It isn’t just the sag when the machine is sitting static, it’s the deflection of the bed when the router plunges. Adding feet to the middle should work pretty good too.
Dan
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I know of a few people who have cut a piece of 1-inch rigid foam to fit beneath the entire bed. That’s what I’m planning to do. Seems to address the issue sufficiently.
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Good to know. I’ll check out if my sag even matters and add feet if necessary.
With the foam, is it sitting under the frame too? Or is the difference between the frame/wasteboard just absorbed by the foam?
On mine I used some thin spacers I cut from MDF under the parts that didn’t make contact with the rubber mat I used, but I let the mat absorb the areas where there are PEM nuts.
Pictures of my setup can be found here:
Dan
This is what I did, MDF slabs under the wasteboard on the bench - and used a few dabs of silicone to stick the whole thing to the bench where it sits. I did find that to keep it flat I had to stick bolts in the foot threads and “jack up” the ends of the frame or it crowned the other way. I could get really fine adjustment in flatness by tweaking the bolts.
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I posted same question one individual took a nice peice of 3/4 plywood and replaced the mdf. That was his sugestion.
It would be nice for carbide to address this issue and fix it permanetly or give the parts out to address it. I have an xl but want to upgrade to the xxl.
Carbide can you reply to let us know what you are doing to address this sag in the xxl. Like to hear their thoughs
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I replaced mine with 1" marine ply, and removed the levelling feet. I put mdf on top and surfaced it and haven’t looked back 
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So all i did was put a 6x6 piece of 3/4 mdf in the center, leveled the feet and perfect, No sag anymore.
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Now that you’re done, another option for anyone else reading this thread -
Remove the feet, knock out the PEM nuts and bolt the frame to an mdf torsion box.
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