Newbie- EMC Issues

[highwaymancnc]

Hi I need some explanation of how to setup emc each time I start a new project. 1st I plan to do 3d machining and engraving on various thicknesses of stock and need to know how to set the machine's Z value for the material's 0.00 location as opposed to the the table's 0.00. I would like to able to just do this by jogging to the material height and then setting it. Is this possible? 2nd, my table size is 12 X 24 X 6 but for most of the work I think that this won't be used much at this expanse. Should I create several INI setup files for various job sizes this may also apply the question one above as well. 3rd the MAX_LIMIT MIN_LIMIT units in the INI file are what exactly. Are they in inches if I use Inch INI and millimeters if I'm using mm INI or or they in the machine units (REVS/INCH or REVS/MM)? 4th, regarding the same settings MAX-LIMIT etc, why do I see minus values in the INI files, I realize I might want to have a slight negative value so the axis can run past the home position and then move to the exact home at 0.00 but in most of the examples I see + and - values are equal, could you explain this as well. Last, should I set the HOME and LIMIT switches just above and below the software limit settings so as not to turn off the machine or does the software take this into account and treat it as a warning rather than cutting power to the driver board? My machine is a home brew unit 12 X 24 X 6 (XYZ) with steppers driven by a 1/2 stepping Hobbycnc driver board, direct drive stepper to 5/16-18 threaded rod and separate home switches for each axis and max limit switches in series for maximum axis limiting. Thanks in advance for any and all help.

[cyclestart]

Nobody? Here's a stab at a couple of the questions

Originally Posted by highwaymancnc I would like to able to just do this by jogging to the material height and then setting it. Is this possible?

That's why we have touch-off. No different than setting x or y. Unless you have a way of setting predictable tool lengths. In that case check into the use of G43.

2nd, my table size is 12 X 24 X 6 but for most of the work I think that this won't be used much at this expanse. Should I create several INI setup files for various job sizes

No reason I can think of.

MAX_LIMIT MIN_LIMIT units in the INI file are what exactly. Are they in inches if I use Inch INI and millimeters if I'm using mm INI

yes

why do I see minus values in the INI files...... could you explain this as well.

My guess is the same as your's. Someone will likely come along with a clear explanation.

[cyclestart]

Limit switches and soft limits are a popular topic the last few days on the user-mailinglist. Go to the contact page http://www.linuxcnc.org/content/view/4/8/lang,en/
and click on user archives if you are not subscribed. Many questions answered there that are glossed over in the docs.

Do you have experience with other cnc controls? This info helps others answer your questions.

[Big John T]

Some values in the ini file such as homing use the minus sign to denote direction.

John