pos/neg direction question

[oldhack]

i still dont understand the difference since there arent many tuts on this. If youre standing in front of your machine.(4x8 Table)what i read in one tutorial was that using the UP arrow should move the (gantry) DRO Y (FORWARD)in a postive movement(away from you) the right arrow moves X axis (RIGHT) in Positive and PG UP for Z in Positive (UP). Backwards the DRO goes down. Is that right? SO I have to set this up like this so the gcode files run properly?
Currently when I zero the Z to the top of my workpiece would that be a negative number? So far all i have done is drive the router into the table. Tried the rrunner file and a scorpion file and neither code goes very low, but the file starts out okay and then will drive into the table until i stop it. So Im thinking maybe it all has to do with the pos/neg positions being backwards or wrong.

Any help figuring this out would be great.
Im stumped so far.

[Torsten]

Well it can get confusing with all the different Machine configurations.
Regardless of what is physicly moving may it be the Headstock or the Table, allways look at it from the perspective of the Tool.
When a X-Axses is moving in the positive direction this could mean the Headstock is moving to the right or the Table is moving to the left, same thing the Tool will always move relative to the part.
For a beginner in Cnc it often makes sense to establish your Z zero position on the Top of the Part, now any positive Number means your Tool is above the Part and a negative Number will be below the Top of the Part.
In Manufacturing of complex Parts with multiple Setups the Part Origin of the Design Model is usually used to estabish the Axis System, so the Zero Locations of the Part could be anywhere.

[kvom]

One way to look at coords is to reference the zero point on your plans. From there, everything "above" is positive Y, everything below is negative Y. Anything to the right is positive X, and everything to the left is negative X.

Similarly, the sign of all movements is equivalent, based on the current position, so the UP arrow means a positive Y move.

[ger21]

Here's how your axis needs to be set up.
http://www.xmlcreate.com/NCGuide/Bas...basics101.html
You can swap the X and Y by rotating the entire coordinate system, but you can't just flip a single axis, or you're parts will be mirrored.

When you zero the Z axis to the top of the work, going down (cutting moves) are -Z, going up is +Z.

You need to understand what the g-code is going to do when you load it. If you load your g-code, and go to the settings page, you'll see the program limits. The first number next to the Z axis will show the depth of cut. The roadrunner should only cut .1 deep, from the top of your stock.

[neilw20]

The signs you have are correct.
In my opinion it is best to set the cursor keys to move in a logical direction.

If a moving table, then the left key moves it left (X+), and the up key moves it away from you (Y+).

If it is a gantry type machine having the key pointing in the same direction as the gantry moves may make more sense. It depends on your perspective and logical expectations.

If you use a key direction, just to satisfy someones 'standard' and you find yourself accidentally moving the wrong way often, then swapping the keys used can help prevent manual crashes. -- oops!.

In both configurations, if the top right corner of the job is set to 0,0,0
then all negative numbers are 'in' the workpiece.

Depending on the job 0,0,0 may end up at some arbitrary position other than one corner, so it is quite normal to have negative and positive XY values, but usually the top of the workpiece is Z0 and negative is where you end up drilling a hole.

[Al_The_Man]

Originally Posted by oldhack i still dont understand the difference since there arent many tuts on this. If youre standing in front of your machine.(4x8 Table)what i read in one tutorial was that using the UP arrow should move the (gantry) DRO Y (FORWARD)in a postive movement(away from you) the right arrow moves X axis (RIGHT) in Positive and PG UP for Z in Positive (UP). Backwards the DRO goes down. Is that right? SO I have to set this up like this so the gcode files run properly? .

One of the problems in translating the axis coordinates comes from the fact that standard cartesian coordinates are specified as relative to the movement of the spindle.
For example to move a spindle in the X plus it moves to the right of the operator, Y in the plus would move away from the operator, this is OK on a Gantry, but as in the case of a mill, the spindle is fixed, so the table has to move in the opposite direction to keep these directions relative to a moving spindle.
Al.

[CNCRim]

Hope this HAAS manual will help you clear up some of the question you have.

http://rapidshare.com/files/33603070...llhandbook.pdf