Alignment after sanding?

In my latest project, I am cnc routing a cribbage board that is basically rectangular in design. Once routed, I do some sanding to remove the tabs, as well as some light sanding of the overall piece to remove any witness lines, while trying not to manipulate the overall size any more than I have to. From there, I am using the 90 degree corner alignment method by cutting a thin piece of acrylic or wood on the laser in order to properly align the cribbage board. Here is where I run into trouble. Because it is quite noticeable if the engraving on the board is off by even a bit, has anyone come up with a solution to slight size changes. My only thought was to use a template large enough to laser cut out the entire profile size of the cribbage board, then set the board in the center of the jig, using shims on either end to "Split the difference". Open to any suggestions. Thanks, Marc

I assume you're using a Chinese machine?

The answer is to setup rulers/guides on the top and left of the machine and setup the home so that it's at the intersection of the two guides/rulers. Then you have a repeatable method of engraving objects. You just have the make sure the laser head homes correctly and you should be good to go.

As for the size changing through the finishing process, adjust your file before running. So if you have a 6"x18" board originally and now it's 5.875x17.875. Don't run it as a 6x18 but as the actual dimensions.

I once saw a picture of a jig that stays in the laser, nothing more than a piece of hardboard with 4 pins extending up. The Blank is placed on the same kind of hardboard slightly bigger than the blank and having holes to match the pins from the lower hardboard.

Placement was trial and error with a laser outline on masking tape slightly bigger than the Cribbage Board. The Cribbage board is double stick taped to the upper hardboard. In this case removal for sanding would work as long as you did not remove it from the upper board.

AL

Are you accounting for the thickness of the kerf when cutting the fixture on the laser?

How about:
1) laser a 2-layer stacking acrylic fixture with dowel pin indexing. Undersize the holes a few thousandths. Drill with drill press.
2) keep the bottom layer in the laser.
3) CNC same dowel pin indexing hole pattern into another piece of acrylic and keep on CNC
4) affix top acrylic fixture layer to underside of wood
5) align on CNC using dowel pins
6) align on laser using dowel pins

In a nutshell, don't rely on the origins of both machines lining up. Rely on the dowel pin hole pattern.