Re: [CAD_CAM_EDM_DRO] Re: Newbie: Two halves of simple die not aligning properly - Long

kaptainkarst wrote:

>I have found where the error is. However, I'm not sure how to correct
>it. This will probably be a post for the Shoptask forum.
>
>My X and Y tables are not traveling perpendicular to one another. I
>can dial in one Axis and get it within .001 over 8" of travel but
>then the other Axis is out by .02 over about half that distance!!
>
>

It depends on how the machine is built. Orthogonality checks on the
axes are one of the things that machine builders have to do to prove the
machine is accurate.

On Bridgeport machines, the ways are hand scraped to an accurate
alignment, using precision hand-scraped squares and straightedges.
There is no adjustment for axis orthogonality. Many other machines
are made about the same way, a "saddle" of some kind has ways
that are supposed to be at a precise 90 degree angle. If the saddle
is made wrong, it can be quite difficult to correct. If your machine is
in warranty, you might be able to get a replacement saddle. If the gibs
are loose, however, it may just be cutting forces deflecting the machine
across the slack in the ways. After the machine has worn in a bit, you
may need to tighten up the gibs.

So, your error is 20 thousandths over 4 inches? I get arctan(.02/4) =
0.29 deg.
or zero degrees, 17 minutes of angle. You ought to be able to see this
error
with a carpenter's square! (Although it would take careful work and good
lighting.)

If you are out of warranty, than you have to either buy a replacement part,
or re-fit it yourself.

I'm guessing the saddle spans about 4 inches, so that means that one of
the dovetails needs to be cut back about .020" at one end, and the
other side needs to be cut back on the opposite corner about .020"
and then the angled side of the dovetails need to be made straight.
Really, only the dovetail side opposite the gib needs the serious flattening
and fitting, the gib side just needs to be relieved to avoid binding.

You need to be real sure of your measurements and your measuring tools
before you dive into something like this. But, once you are confident you
can measure the error without any possibility of mistake, you should be
able to decide how to proceed.

For sure, this error needs to be corrected before you attempt to make any
precision parts.

Jon