Setting Zero

Just curious how others are setting program zero with TurboCNC.

I like to do it this way:
MDI mode
G91 (incremental)
G0X___Y__ Z___ (to jog close to program zero)

FOR EACH AXIS:
G0Z-.1
G0Z-.01
G0Z-.001(use the arrow up key to reissue move as necessary)


G90 (ABSOLUTE MODE)
G92X0Y0Z0 (set zero)
G0Z1.0

Exit MDI goto automatic and run program.


Every tool change I repeat this for the Z axis.

I tried the JOG mode, but I find I am more likely to make a mistake by having the pointer selecting the wrong axis when I make a move or set zero.

Bill

Hi WJB,

IMO, I think your method forces you to have your tool home position at the XYZ0 of your part. If you want more room in order to change tools, you can also jog (or perhaps make an MDI move, I don't know your controller's capabilities) away from the work "datum point" ($10 word for your part's chosen reference point).

Say you use an edge finder to pick up the work corner. Then, with the spindle set right over this corner, you can set all axis to zero as you may already be doing.

Then, move clear, lets say to X-2.0 Y-2.0 with the tool raised at Z1.0

Now, rename this position G92 X-2. Y-2. Z1. This allows you to describe any tool position you like in reference to the workpiece's coordinate system. What I'm trying to say, is you are (likely) not locked in to using the work's X0Y0Z0 as your only G92 home option. G92 home is relative to the work's X0Y0Z0, but doesn't have to be at that location.

A word of caution: I usually include the G92 line in my program. This makes the assumption that the machine has always returned to home before the program is re-rerun. I have shortcut methods on my controller to get back to this home position, even if I abort or E-stop, but it is imperative that you must be at this position before allowing this line to run in automatic mode.

The latest version of turbocnc 3.24c, allows you to jog the z with the pgup/pgdn keys. I have found this to be very helpful. It's only available at the yahoo group files section.

Eric

Since I currently only do one off parts and use odd size stock. I just load the g-code part and then go into "Jog" mode and bump each axis to the corner of the stock and hit the "Z" key to zero type a zero (or any other key) and then enter. That zeros all 3 axis at the same time then I go run the program. I don't have home switches installed at the moment so placement jigs and repeatable placement based on home is not an option for me (yet).

if i were to use turbocnc with the xylotex driver, would i have to set 0 each time i turned the machine on and ran a new program?

Turbocnc remembers the position of the tool when you exit, so if you turn everything on, as long as you didn't manually move the machine or move it with another porgram, it will be in the correct position to just carry on. I generally rezero it tho to be sure.

Eric

what about using limit switches in the home position of the x and y?

that works too