XY interpolation for fixture realigning?

[jacmac]

Looking for some ideas or feedback on a feature that I sorely need. Here is my issue and proposed solution.

I'm going to make a fixture that holds 4 sides of a metal box. All features in the "faces" of the sides of this box are 2.5D, various holes, slots, etc. All 4 sides are milled at the same time and everything works great (I've done this before). I mill the features of the fixture AFTER a secure it to the spoil board so everything is perfectly square to my mill, if that makes sense. The issue is: My mill is multi purpose and so sometimes have to take the fixture off and mill something else. My neighbor asked for a "heart" for her tinman windchime...

I take the fixture off do the other little project and then put it back on and try to align everything back. I usually engrave a little X-Y cross that I can then ZERO X-Y with, but it always occurs to me that there could be RACK and or SCEW that is not accounted for.

I dream of having two X-Y crosses and opposite ends of my fixtures where I can ZERO against one and then move over to the other, let's say it's supposed to be X10 -Y10. If it's off I could ask the software to interpolate, or otherwise even out the error? Does any of this make sense!?!?

[Bubba]

Why not add a alignment holes in your fixture and your table. Use close tolerance pins and bushings. make not of the exact XY location. This way you be able to remove reinstall the fixture anytime confident of the location. I have made multiple fixtures with tooling holes and have set of bushings installed in the table. Saved the location XY in Mach3 as an offset (my case offset #57) . All I need to do home my router spindle, set xy zero , recall offset 57 and go.. Hopefully this helps. Good Luck.

[jacmac]

Thanks for the idea, but I already use alignment holes. It's a big fixture. Almost the entire length of my millable area. I still think I way to even out the error for me would be good. Maybe it's too complicated?

[lloydsp]

I just use the 'three pass' method for aligning one axis of a jig.  I use a ball-nosed 'indicator bit' (with lights) in the chuck, and manually align and lightly clamp both ends of the fixture as well as I can before I start.  Then I go to one corner.

I align that corner, and ensure the clamping, then make an excursion to the opposite end, and align it as closely as possible, and ensure it is still lightly clamped.  Go back and forth three times, and you'll be within a half-thou' over the entire length.

It takes about the same time to do as it does to describe.

Lloyd

[dh42]

Hello

I dream of having two X-Y crosses and opposite ends of my fixtures where I can ZERO against one and then move over to the other, let's say it's supposed to be X10 -Y10. If it's off I could ask the software to interpolate, or otherwise even out the error? Does any of this make sense!?!?

Certainly, this can be done, but maybe not with CamBam but with your driving software.

Example, on Mach3 you can write a small script to do the angle calculation between your two crosses after probing each so you know how many you axis is tilted from the axis.

Then you can use a G68 to rotate the Gcode around its origin. (or the rotate function of Mach3) as on the picture.

++
David