CNC Marker Test

 
We use this handy tip from time to time to determine to path of the cutter long before the chips fly.

CNC is awesome, but to actually know where the cut will be BEFORE the cut is made is second to none.  I use this technique when making fixtures and other large cut from stock operations.

About our fixtures:  We make our fixtures from cast aluminum slabs,  we start with all the cut off bits and pieces and cast them into a 6"x24"x1" solid slab.  The slab is then decked both sides, hold down bolt holes and alignment pins are added.

The G code to make the fixture is then generated, we work to center the recesses between the bolt holes ,alignment pins and to make sure the fixture is utilized to the fullest extent.  As such we may run this "Marker Test" a few times, each time changing the offsets just a pinch.

 
 
With the metal mounted, everything is wiped down with a cleaning solvent, lacquer thinner or alcohol works well. 
 
The marker is chucked in the collet, we use a 1/2 collet and put 2 wraps of tape around the marker. 
 
Run the program as normal, just make sure your code only touches the surface.
 
The drill pattern looked good and was run, here we're running the cut sequence one more time.
 
Looks good to us.