Setting top of piece

[davel]

I just assembled my machine and got the G-code sender working.  I am going to hook up the homing switches tomorrow.  I am planning on using Vcarve to generate the file for my first cut.  In Vcarve, you set the wood thickness and then indicate whether Z Zero is the top or the bottom of the wood (I am using top).  It looks like the homing operation sets Z to the highest possible point.  After you install an end mill, how do you set Z Zero on the machine?

[Derek the Admin]

Yes, the homing cycle will home all axis to the high side. That's the convention in CNC routers and clears the work space to receive stock for clamping to the table.

The most basic way to do this is to jog the machine to the origin and slowly drop the Z a little at a time (first by 1mm then by 0.1mm when you get close) and to move around a piece of notebook paper between the bit and the stock. Once the paper drags between the stock and the bit you are essentially at the top of the stock. Type G92 Z0 or click "reset Z" in universal g code sender. That would set the Z axis zero to the right height. The "origin" that I'm referring to above is the origin of your cutting file. Let's say for instance you had a piece of wood that was 8 inches by 8 inches and you had a design that you had generated code for that was 6 inches by 6 inches. I'd clamp the 8x8" piece of wood down at it's edges (obviously) and jog the machine to about 1 inch from the bottom left corner. I'd call that point my "origin" for the cutting file.

As an alternative, you could set up one of the "permanent" work coordinate systems using the G10 command. This is more complicated so I'm going to spare you that for now. There is a decent primer in the quick start guide at www.millrightcnc.com/resources if you want to get acquainted with those concepts. I'd be happy to delve more into that if you want.

I hope that helps.