Z axis triggers limit switch at the start of each job

Software Help Fusion 360
1

Hi:

I’m having trouble with my inductive limit switch on the z axis. Every job I’ve attempted to run today, the router rises an triggers a fault and I can’t proceed, I had this problem once before when I had my Z and Y axis mixed up, that is not the case now.

Is there a step-by-step G code debugger that I can run? Alternatively, I’ve attached the g code below, I have a feeling it is the z15 (8 lines from the bottom of the snippet) that Fusion 360 adds automatically and has not been an issue in the past. Any help would be appreciated!

thanks,
Shawn

(Machine)
( vendor: Autodesk)
( model: Generic 3-axis Router)
( description: This machine has XYZ axis on the Head)
(T5 D=6.35 CR=0 - ZMIN=-3.5 - flat end mill)
M8
G90 G94
G17
G21
(When using Fusion 360 for Personal Use, the feedrate of)
(rapid moves is reduced to match the feedrate of cutting)
(moves, which can increase machining time. Unrestricted rapid)
(moves are available with a Fusion 360 Subscription.)
G28 G91 Z0
G90

(clear for display)
T5
S5000 M3
G54 G0 Z0.5
G0 X69.856 Y42.787
Z15
G1 Z5 F1000
Z2.55
G3 X65.114 Y40.905 Z2.341 I-1.709 J-2.609 F333.3
X68.485 Y37.084 Z2.133 I3.029 J-0.725
X70.938 Y41.543 Z1.924 I-0.342 J3.092
X65.918 Y42.343 Z1.716 I-2.791 J-1.366
X66.862 Y37.354 Z1.507 I2.227 J-2.162

2

Z15 should be a move down to 15mm above your Z0.
The problem is most likely the G28 command. Do you have a G28 set?
For most users, I’d recommend disabling G28 retracts when you post process.

1 Like
3

Thanks! I realized that I used a different post process in Fusion 360. I did a software upgrade and lost the one I had saved (Carbide Create Post Processing option) and I tried one called “Bob’s CNC”. Mistake.

Now I can compare the two and see if the Bob’s has a G28 set.

Thanks again.

4

When you post process there is typically a checkbox or a dropdown selection for those retracts. Is it says G28 retracts, uncheck it. If it gives you a choice, don’t choose G28. If it doesn’t have a way to choose, pick a better post processor. I’d share mine, but I don’t have a LongMill.

5

Hi:

I found the checkbox and I’m all set. thanks

1 Like
6

Just to clarify for completeness.
There’s nothing wrong with G28, but most people don’t use it. By default, the G28 location is set at machine zero (typically, your limit switches). But you can set G28 to be anywhere you want.