Is there an established CNC/machining way to really, precisely locate fixtures/bed/vise/etc.?

So, I could puzzle something out but I don’t want to reinvent the wheel.

Is there a way to really, precisely locate stuff? For example, I don’t think rapid-positioning to the center puts the endmill right on the centerline of the vise channel or bed reference holes. I was thinking I could mill a rectangular block that would fit in the vise channel or flip jig, carve a small horizontal line in it at what I think is Y center, rotate the block 180 degrees and carve another horizontal line in it at what I think is Y center, and then measure the error offset between them, and then I’ll know that what I thought was Y center is off by 1/2 the offset.

Better yet, I could carve diagonal lines (one from upper left to lower right, then rotate block 180 degrees and carve the other from upper right to lower left), the shallower the slope the better, and then the offset distance in X will inform how wrong my guess at Y coordinate center was. e.g. if I carve lines of slope 1/10 and the place where they cross is off by .06 inches to the right, then I’ll know that my guess at the Y coordinate was .06/10/2 = .003" too high.

Similarly, I have a need to locate the left vise wall, or locate the position of the left wall of some softjaws that I made and I guess I could do a similar thing.

I was just wondering if there are established CNC/milling routines for doing things like this.

The way I address this for myself is to make a fixture — I include a reference hole in it, which the endmill should fit into — assign a workspace coordinate system to it if it’s one I use often, or keep a note on what the offset is for it and change one of the WCS as needed to use it. See:

http://www.shapeoko.com/wiki/index.php/G-Code#Using_the_Work_Coordinate_Systems

1 Like

@WillAdams AWESOMELY points to a technique commonly used in fixturing - the touch off point.

On systems with electronic touch, one navigates over the area/hole and the machine does a touch - to deal with Z - much like the tool sensor.

It’s not uncommon to NOT precisely locate things. The fixture holds the part and one zeros to the part. That’s easier said than done… but machines like Datron do the edge finding for you.

Another technique are standard holes in the stock - reference holes - which are used to bolt/screw the stock down to known positions in a sea-of-holes (for this part use these holes). The G54-G59 G codes for recording positions are often involved.

mark