Need Help!- Excessive Table Flex

[esp173]

Since I completed the Machine Tool Camp 4' x 8' router build last summer, I've been frustrated with the deflection in the table. The machine does quite a bit of flexing over it's length and width because it's essentially a 10' clear span with no supports in between to add stiffness. It's difficult to achieve a consistent cutting depth on large pieces. Often, when cutting at a single depth setting in the software, the actual piece might vary in depth by +/- 1/8". It seems that doubling or tripling the layers of MDF that cover the table help reduce this flex, but I loose much of the little z-height clearance that is available.

Question to anyone with an MTC or similar build: Have you discovered any other ways to add rigidity to the table?

On this particular build there is some clearance between the gantry and the table beams (I've outlined this red in the photo). Aside from adding layers of MDF to the table, some steel tube might be attached to this beam to add stiffness. Any thoughts on this? Has anyone tried it?

Thanks for reading,

Justin

http://picasaweb.google.com/lh/photo...eat=directlink

[jsheerin]

I don't have this exact machine, but I have one like it and I have cross rails under the material. This works pretty well for me. See pic:

[esp173]

Thanks for the suggestion. I have my racks and stepper motor running on the inner T-slots of the long spanning beams. This makes it difficult to do anything in this area to add stiffness. This design was attractive to me initially because it protected the linear guides, rack, and motor from dust (underneath the table). Now the table flex is so problematic I would much rather risk the increased dust exposure by mounting these elements on the side of the beams (similar to what you have shown in your pic).

[metalworkz]

Justin,
Do you think you could run the support rails from end to end instead of from side to side and perhaps accomplish the support needed without interfering with the rails? Just a thought.

[ger21]

Build a torsion box, or 2 or 3 shorter ones, and mount it between the rails. My router uses a 30x60 torsion box supported only at the ends, and can support over 200 lbs with less than 1/64" deflection.

[esp173]

Thanks for the suggestions. I'm currently rethinking the design to include more support for the table—a torsion box is definitely needed.

Justin