Fusion 360 G code not cutting to proper depth

Hi all,

I generated some G code in Fusion 360 for a cog at 3/4 " (-19 mm) depth cut. The G code looks correct: however, when I execute the program it only cuts about 5.3 mm deep. I cant see what’s wrong. Can anyone help please? Thank you in advance!!

Here is my header:

(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.)

(STOCK/BLOCK,203.2,203.2,19.05,0, 0, 0)

And end of code…


Looking at the code, everything seems fine.
By chance is your $102 set wrong?
Does the Z drive the correct distance when it’s commanded to move up or down manually? (the more distance, the more accurate this value will be)

I checked Z movement and it is precise. A jog of 1" results in 1" movement.

I’m grasping at straws! Thanks though!

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Are you using a GRBL post processor? I eliminate all non critical Gcodes in my files that I make using MS Notepad, as I use a generic post processor and it adds a bunch of stuff I don’t need for UGS. I don’t use Easel.

I am using a GRBL post processor. At first, I used the Easel post processor in Fusion 360 which didn’t work. So, I downloaded the f360-easel.nc post processor downloaded from the Inventables website. No joy either. I’ve opened the files in notepad and, though I’m new to g code, it seems like the settings are OK. However, as you noted, there are several lines of code that seem superfluous.

For what I’m trying to make (a wooden gear) I need the outside of the cog and a hole in the middle. The hole in the middle uses a 1/4 inch bit and when I ran it the gcode worked OK.

For the gear, I’m using a 1/8 inch bit but this code seems like the step-down isn’t working even though the correct Z position is specified in the program.

Never fails when I try something new I have to run my face into a brick wall a few times!

Well as a work around can you do a toolpath around the perimeter of the gear drawing that is offset.0625 outside the line and offset .0625 inside the line hole? Then you could do a straight engrave carve with a .125 tool. Maybe it is a setting in Fusion that is screwing things up? I use Rhino. I found fusion less user friendly after all my time with Rhino. I also use 2.5 D for most simple things that don’t have a curved contour on top. Basically I’d do a toolpath for the gear and hole, then do the CAM. Then copy and paste it in Notepad and adjust the Z depths for as many passes as I want. Sometimes it is less work than doing a 3d carve, depending on the part.

So you copy one pass and paste it multiple times adjusting the Z downward for each pass?

I’m happy to report I’m an idiot!

The gcode was running correctly but there was so much finely packed saw dust in the grove it looked, and felt like solid wood! When I took the work piece off, to my shock, the piece had cut through! Man! Do I feel dumb! Thanks all for your kind help!!!


Yes, this stems from starting the cnc hobby back before sophisticated software was available and affordable. I actually bought a book to learn how to write Gcode because hobbiest Cam was very primative. My first project was a sleigh xmas tree ornament that I wrote all the code for.

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G code is fairly easy to read but I’m sure it is hard to write from scratch and make all the parts work. That’s why I was so surprised when I thought it wasn’t following the Z commands. I’ll study up on it more. If you have a good reference I’d be interested in getting it.

Thanks again!

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I left the book with the cnc machine I made ( I was a shop teacher and retired). I’m sure I got it online but Amazon wasn’t around then…LOL. Something like this probably would do the basics. The hard part was trying to get half arcs and stuff like that. With I’s and J’s as well as the X, andY’s.

Quick G-Code Arc Tutorial: Make G02 & G03 Easy, Avoid Mistakes (cnccookbook.com)

GCode Tutorial

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