help needed on fusion 360 and g code

[terry1956]

hi. I am using fusion 360 to write the g code and then downloading it to mach 3. but when I start the milling program the tool just starts to drill into the work piece. the first line of the program is

G90 G94 G91.1 G40 G49 G17



I am sorry I don't have any means to cut and paste the rest of the program. can anyone help me out. at a lost what to do.

[Ger21]

The first line has nothing to do with why it's drilling into the work piece.

Also, someone needs to fix that post, as G90 and G91.1 should not be on the same line.

[komatias]

The first line has nothing to do with why it's drilling into the work piece.

Also, someone needs to fix that post, as G90 and G91.1 should not be on the same line.


The MAch3 post as it stands in Fusion has some issues that I do not like either. For example it uses g91 and g91.1 that make your code be incremental and not absolute. I only noticed that it was using these as Ger's screen has a nice bar at the bottom telling what is active.

The Linxcnc post is significantly simpler and I would recommend you give that one try.

[JAZZCNC]

Terry just up load the txt file because without it there's nothing we can do to help.

Like the Lads say Fusion 360 Post processor is screwed up by the looks but without seeing the G-code it's impossible to tell what it's doing.

[Ger21]

According to the line above, it uses G90 and G91.1.
The problem with them being on the the same line, is that if you are in G91 mode when you load the program, it won't switch to G90.

[terry1956]

hi, this is the full g code to face the part.

(WHEEL SLOTS CUT FRONT FACE WHEEL FIRST CUT 3MM)
(T1 D=3. CR=0. - ZMIN=0. - FACE MILL)
G90 G94 G91.1 G40 G49 G17
G21
G28 G91 Z0.
G90
(FACE2)
M5
M9
T1 M6
S5000 M3
G54
M9
G0 X38.7 Y1.357
G43 Z15. H1
Z5.
G1 Z0.3 F333.
G18 G3 X38.4 Z0. R0.3
G1 X36.75
X0. F1000.
G17 G2 Y4.185 R1.414
G1 X36.75
G3 Y7.013 R1.414
G1 X0.
G2 Y9.842 R1.414
G1 X36.75
G3 Y12.67 R1.414
G1 X0.
G2 Y15.498 R1.414
G1 X36.75
G3 Y18.327 R1.414
G1 X0.
G2 Y21.155 R1.414
G1 X36.75
G3 Y23.983 R1.414
G1 X0.
G2 Y26.812 R1.414
G1 X36.75
G3 Y29.64 R1.414
G1 X0.
G2 Y32.468 R1.414
G1 X36.75
G3 Y35.297 R1.414
G1 X0.
G18 G3 X-0.3 Z0.3 R0.3 F300.
G0 Z15.
G17
M9
G28 G91 Z0.
G28 X0. Y0.
M30

[magicniner]

The MAch3 post as it stands in Fusion has some issues that I do not like either.

So they're not adequately supporting the most common controller software in the world?
:-D

[komatias]

So they're not adequately supporting the most common controller software in the world?
:-D

Not sure people have actually submitted tickets to get the issues fixed. I haven't done so as I have learnt to live with it.

[terry1956]

Hi.so the fault is something between the way the g code is written by fusion360 and the way mach 3 reads it. Ok but what is the fix?..

[komatias]

In the post processor option, use the linuxcnc option. Cannot remember off the top of my head how it is described.

Are you confident that you have the CAM model set up correctly? I can take a look for you if it helps. PM me your email and I will give you directions on how to do this.

[cncJim]

Hi Terry,

I am just trying to understand what problem you are having. I put it into NC Corrector to try and visualise your g-code (I am just leaning g-code so this is a bit new to me).

What position are you starting from (xyz?) and when you home the machine where does it go (xyz)?

Line 5 (G28 (return home) G91 (Incremental distance mode) Z0). I guess this means it will home the X and Y axis but leave the Z same position?

So what is mach3 doing?

Cheers,

Jim

[terry1956]

Hi.on the setup cnc section I set the home position at the top of the material block lower left hand corner. When I set the material up on the machine bed.i jog the cutting tool to the lower left hand corner of the materials top face and then set all the axis to zero.i use paper between the cutting tool face and the material surface to cap zero. Then I download the g code. On the run the tool just drills deep into the material and I need to end the run.if its not the machine code then it must be something I am doing wrong.michael

[JAZZCNC]

There are no Negative Z axis moves in that G-code so it will not cut anything using the way you set it up. It certainly shouldn't plunge down.?

Have you cut anything with machine before.? It could be that Mach3 is setup wrong regards the Steps per setting so it's moving further than it's being commanded.?

[Washout]

Just an idea - when my machine starts any job posted from Fusion 360 it does a full retract to the machine's Z axis zero point i.e. full retract to the "up" limit and then continues the job. Its not going to the stock or work zero for Z axis. This is a "safety" feature I think in the Fusion 360 post in order to ensure the work piece is cleared from whatever starting position your tool is at.

Sounds like you may have your machine set up so that its Z axis machine zero is either at the top of the work piece or on the bed and the full retract my machine is performing is a "full down" to the bed move (machine zero) on your machine before continuing.

Hope that helps.