pic: Dual FP gearbox

[artdutra04]

Originally Posted by CraigHickman

Those distances added to the center to centers all depend on your plate material, stiffness, machining capabilities, and so on. The team I've worked with has always been fortunate enough to work with a machine shop that could hold true to .0001, so we never really saw a need to design around the machining equipment.

What will these be machined on? If you find what tolerances they hold, it'll be easier to identify what spacing you need.

Even if you can machine things to high tolerance, if you can design them to work under less strict tolerances you'd drastically cut down on the price of the component in the real world. I've seen instances where moving from 0.005" to 0.010" tolerances on all non-critical dimensions on a part cut the price nearly in half.

Originally Posted by s_forbes

Our current plan is to try machining gearbox plates on a manual mill. We have access to a big one at our robot building facility, and there are a few high end ones in the AME department machine shop at my college. Hopefully we can keep all of the center to center distances within a thousandth, so it will probably work fine if we aim for 3 thousandths over nominal distance (I hope). If we get around to making something like this, we'll see how it turns out.

Does this mill have digital read outs?

If it does, then keeping tight tolerances isn't generally too bad. But otherwise, you better be the master of feeling the backlash in the ball screws of the table to keep tight tolerances. But seeing how almost all of your holes are in the same line, even if you don't have DROs, you can keep precise (though not necessarily accurate) tolerances as long as you never overshoot your target distance (read: you are always staying on one side of the ball screw backlash).