Sunday, June 11, 2017

CNC router: Upgrading the Z-axis - Alignment

I have noticed recently when planing a surface with a cylindrical cutter, there is a step of about .020 inch per inch in the Y direction.  My Z axis is not quite perpendicular to the Y.  I already want to redesign and rebuild the z axis because it is not stiff enough to resist cutting forces in the Y direction to my satisfaction.  As I design a new base for the Z axis, I need to get the mounting holes in the right place to correctly orient Z to Y.  My solution is a test plate with the following pattern:
The program puts center points for the two mounting holes along with a set of horizontal lines.
The G-Code is so simple, I just wrote it in a text editor.
I used the program to cut a piece of hardboard:
Then my computer crashed...
A week and a $10 hard drive later (Thanks, Habitat for Humanity Restore!), I drilled out the holes and mounted the board on the saw.  Then I fixed a pencil in a board and drove the y-axis to mark a line across the board:
As you can see by the angle between the pencil line and the horizontal groove, there's a bit of error in my original measurements, so this will help me get it right.

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