A problem with milling Z

[Cocoabutter]

I made a model which is the size of my stock, and in it i am trying to cut a very simple desihgn. I used 2D adaptive, and 2d pocket (( its just a pocket 2mm deep)) and both give the same result. When i post process the operation it starts my Z at above 0, which i have set to the top of the stock on the cnc. I cant get it to run the Z as starting from zero and going negative. it starts at Z+ 3 and moves to Z-1ish. Is there a way in fusion to make it so that it starts at Zero and goes only negative?  If needed i can post my model but it is just a simple pocket.

Thank you for the help!

(TEST 3)
(T8  D=2. CR=0. - ZMIN=-1.5 - FLAT END MILL)
G90 G94 G91.1 G40 G49 G17
G21
G28 G91 Z0.
G90

(2D ADAPTIVE4)
M5
M9
T8 M6
S10000 M3
G54
M9
G0 X28.007 Y95.803
G43 Z16. H8
Z6.
Z3.75
G1 Z3.55 F720.
G3 X27.736 Y97.684 Z3.446 R0.95
X28.007 Y95.803 Z3.342 R0.95
X27.736 Y97.684 Z3.237 R0.95
X28.007 Y95.803 Z3.133 R0.95
X27.736 Y97.684 Z3.029 R0.95
X28.007 Y95.803 Z2.925 R0.95
X27.736 Y97.684 Z2.82 R0.95
X28.007 Y95.803 Z2.716 R0.95
X27.736 Y97.684 Z2.612 R0.95
X28.007 Y95.803 Z2.508 R0.95
X27.736 Y97.684 Z2.404 R0.95
X28.007 Y95.803 Z2.299 R0.95
X27.736 Y97.684 Z2.195 R0.95
X28.007 Y95.803 Z2.091 R0.95
X27.736 Y97.684 Z1.987 R0.95
X28.007 Y95.803 Z1.882 R0.95

[LibertyMachine]

Sharing your model would help greatly.

File > Export > Save to local folder. Return to thread and attach the .f3d file in your reply

[Cocoabutter]

Heres the file! Please let me know of any other way i can be of help. The post process im using is generic mach3 mill that comes stock. My mill is..well.. a genaric mill that runs mach 3.

Mach 3 is set proper and all for what thats worth.

[LibertyMachine]

That's because your Z axis is pointed down in your Setup. You want it pointed up. I don't know your CNC knowledge level, so forgive me if the following is basic stuff for you:

Take your left hand, make a fist. Extend your thumb, pointed at the ceiling. Point your index finger forward, perhaps at the monitor. (You know have a finger gun). Extend your middle finger parallel with your torso.

What's the point of all of that? That was to show you how XYZ positive direction is in the CNC world.

Thumb: Z axis

Index: Y axis

Middle: X axis

[Cocoabutter]

Terribly sorry! i sent the wrong file! i ment to send this one. This is the one i made the post from. i had suspected something like that and i fiddled with it, which is why you got the wrong file. Sorry! This is the correct XYZ in cam, yes?

[LibertyMachine · Accepted solution]

With this model, you do have it setup correct. 

However, the code is proper. Yes, it starts on the positive side of Z, but it does helical down to Z-1.5mm (you have "Stock to leave" set to .5mm). This is completely normal for g-code to have both positive and negative values in the program. If it started at zero (top of part) and only went negative, you don't have any good option for retracting out of the part and going to another location.

If the issue is the amount of time spent cutting air, than that can be addressed by several settings: Heights tab and Ramp clearance height

[Cocoabutter]

ll im wanting my zero to be a few mm above the stock. How exactly would i go about changing those settings to make it a more... acceptable cut? because,  im not just cutting air, its far too high to eb cutting anything.. its rather strange. like i said, i did zero a few mm above the stock.

[LibertyMachine]

If you've zeroed a few mm above the part (at your machine), that's your issue. You need to set Z zero (again, at your machine) as top of your stock

[Cocoabutter]

Thank you  very much sir. My part is now milled! It was multiple things. 1 the ramp height and ect. But my Z kept crashing super low. I looked in my mach 3 and it was sent to auto-rehome for some reason! i took that off, no Z crash. Happy mill owner! Haha! +1 for your posts sir!

First cuts!

http://i.imgur.com/1pWiXuX.jpg

http://i.imgur.com/A9PkNTY.jpg