problems starting prints at multiple / defined point.

[TheSniper]

All,
Lets say I have my build platform dialed in. and to make sure I give enough information.
Lets say the X is 150mm and the Y is 200mm
Im building a small part with an overall footprint of 10mm square

And I want to do one at a time. Cant I just position the print head at the location of my choice and have the machine think Im at Position Zero and then print...
then when done, I can jog it to some other un used location of my choice. then re print. until I have used up all the available space on my table?.
I cant seem to get this to work. the machine always either wants to jog to some corner of the build table or go back to the center.

I will add. Most of the time when I want to print something. I have tried both ways. 1: Home all axis. Jog to center of the table. Set Z and rezero. Start my print. when it starts. it most of the time Does a move all the way to the real Zero Zero of my build table (basically off the build platform)
Second method is the same I just dont zero at the beginning. with exception to the Z axis. What gives???




Is their some tutorial or else?
Troubled.
-S

[JoeJ]

Yes, just replace the G28 command in your starting script with G92 X0 Y0 Z0

If you're new to this, you might want to go read this: http://reprap.org/wiki/G-code

[TheSniper]

Joe,
Im somewhat familiar with g codes. But for the life of me I just get different results.
X=100, Y=150, Z=150
Lets say I have all my axis homes. and sitting on the limit switches. So Im at 0,0,150
From here I lower my print head to the table to set my clearances. and issue a G92 Z0.
so effectively Im now at 0,0,0.
If my part is say 10x10. And when the printing starts the head will move to the center of the table, lower to the first layer height and start printing...
Now if I move the head in the X & Y to where I want the print to start. and then issue a G92 X0 Y0 Z0
then when the print starts the print head/table moves to some other location on the table.

FWiW I have the G28 remed out in my startup scripts.
Help?
S

[JoeJ]

Why don't you post your gcode file.

Also, does your printer actually correctly implement the G92 command? Maybe it is a firmware bug. For example, connect to the printer and then send a G28 to home all axes. Then send the following three commands

G1 X50 Y50 F3000
G92 X0 Y0 Z0
G1 X5 Y5 F3000 <-- watch carefully when you send this command

Does that move just 5mm in the X and Y when you send that last command? Or does it move a lot more back towards the origin?