Re: [CAD_CAM_EDM_DRO] re:Levelling large table

> Hi Doug,
>
> What did you decide to do on leveling the table?
>
> Thanks,
> Joe Fahy
>

Perhaps it was you that gave me the idea of using an oil trough and
micrometer head. This got me started on several new ideas. Here is my
current thinking:

The frame must first be stress relieved or it will change over time. I can
do this with a propane flame thrower - not perfect but better than nothing.
Fine thread jack screws on the legs will provide levelling adjustments.

We will build a trough around the top rails and pour hot epoxy. This epoxy
is 100% solids and has very little shrinkage. The heat is to reduce
viscosity. After curing the dams will be removed and the miniscus filed
away (Smoke pointed this out).

The table will be .625 cast aluminum tool plate bolted to the frame. A
viscoelastic tape will be applied between the epoxy bed and toolplate to
provide some damping and allowance for thermal movement.

I originally planned to put the linear rails on the plate surface. The
Hiwin rep says they work equally well upside down, so I am thinking of
mounting them underneath the plate. Depends on the accuracy of the plate.
This will allow me to use the entire top surface for machining. It will
also serve as a work table and laminating bench. Z accuracy will be
slightly comprimized with the rails on the bottom due to thickness
variations in the plate (up to .005"). However, Z axis variations are not
much concern for my application. I can alway improve it by flycutting the
spoilboard.

The Y axis rails will also be upside down to get them as close as possible
to the bed. I need 24" Z travel and this will help rigidity. The gantry to
bed clearance will most likely be adjustable in three steps - 6" for flat
sheets, 12" for bigger stuff and 24" for foam cored molds.

I plan to use dual X axis screws and dual motors. Need to go up to north
Georgia soon to see Les Watts' machine before I start building though. He
has some brilliant ideas on accuracy mapping.

The rails and screws will be ordered this week.

Doug