Z is off when using fixture

[powell9914]

I am using a fixture to make a Guitar Neck.  I Identify the fixture in the setup. I use the corner of the fixture as my WCS origin because the neck must me moved to different positions on the fixture to be milled. All the simulations work fine. When .nc is taken to my CNC router (Axiom Pro) the Z Heights are all off and The bit will not descend into the cavity.  First cut is supposed to be at Z=82mm but goes to 75mm and stays at that height for every stepdown. G code was checked and proper Z heights are listed. X&Y are very accurate.

PLEASE Help

[powell9914]

So...I confirmed the operations files work when I moved the origin to the stock itself.  So it is an origin or component acceptance/recognition problem.

[jscott6SWZG]

Check your offset from fixture point, to guitar neck?

[powell9914]

All offsets are at 0. Bottom, set Stock bottom. Top, set to model top for all ops except Facing, set to Stock top

[jscott6SWZG]

I meant how is the fixture point related to the guitar neck.  If you set z at the wcs.  How much higher is the neck from the wcs.  

[powell9914]

Block is ~58mm and then ~24mm to Fretboard baring surface. So first cut Should be 81-82mm

[seth.madore]

@powell9914 could you share your Fusion file here?
File > Export > Save to local folder, return to thread and attach the .f3d/.f3z file in your reply

[powell9914]

Sure, Like I said, I know the ops files work and simulations work.  X and Y are accurate, Just the Z is off (cutting way low and staying at z level 75mm).  I have gut feeling How the 2 pieces of the fixture are put together, placed or used are at issue. I just don't know the right question to ask to correct it. File is attached.

[seth.madore]

Looking at your Facing toolpath (first toolpath in your Setup), it's going to 81.805mm, which mathematically is correct (based on your image above):

Are you saying that you don't see if go to 81.8mm at your machine?

 

[powell9914]

On the machine it goes to 75mm and stays there for all Z heights.  Further research, 75mm is the machine's default safety height

[powell9914]

I have an hypothesis, Something is not letting the machine go over 75 Z.  I made victual test blocks at heights 40, 60, 70, 80mm.  Ran facing ops on the machine and yes hypothesis proven. 40,60,70mm ran fine.  80mm ran at 75mm.  So I know its not the fixture.  It is a control somewhere.  The G-code said to go to 80mm, but ran at 75mm. 

WHERE are Z height limits controlled, post? Machine?  Full Z span the machine goes 0 to 150.

[seth.madore · Accepted solution]

This is sounding like a machine/control issue. There's nothing in the posted g-code that's limiting your program to 75mm.

[jscott6SWZG]

so the machine jogs the full z span?

[powell9914]

yes, full 150 where ever the 0 splits it.

[leo.castellon]

It almost sounds like it isn't picking up your tool length offset if you default safety height on your machine is 75mm and everything is running at that Z level. Can you show us your posted G code? How does your machine pick up the length of the tool that is loaded into the machine?

LeoC

[powell9914 · Accepted solution]

So, problem solved. There is a height max control in the menu of the Axiom machines.  Not sure if most machines have that.  There is a check run when a file is started to make sure the op does not run outside of the envelope perimeters.  Are both really needed??

[jscott6SWZG]

Not really.  Soft limits can prevent crashes.  Mine are turned off.  If i had a lot of fixtues and things to crash on i my ght turn them on and set them

[powell9914]

Turns out the machine has a max Z of 75mm to start a cut.  Tool shoulder length is accounted for in the g-code from the tool that is chosen for the op in fusion 360.  But yes, this is a weird one.  You would think it let the Z run until it maxes out at the limit/proximity switch.  There is always an envelope check when the file is started anyway. 

[powell9914]

Thanks to everyone for your input and help!