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ForumCSMIO/IP controllers and Software - discussion forum: CSMIO/IP with simCNC softwareFusion360 4 axis post processor s …

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Fusion360 4 axis post processor seems to no post propertly

#1 · 6 June 2025, 14:13

Quote from ivancastillocaro on 6 June 2025, 14:13
Hello everyone,

I'm still experimenting with SimCNC, and now I'm working on 4-axis toolpaths. I'm using Fusion 360 (with the Machining Extension), but I haven’t been able to successfully generate G-code that works properly with my machine.

The test case is the following:

Im trying to cut a HTD-5M pulley from a 30.7mm aluminum blank. I modelled the pulley in Fusion360 and I'm going to cut it using a 3mm ball end mill. (See first photo)

The cutting strategy I used for this operation is a multi-axis rotary contour. (See the second photo for the generated trajectory)

Now, im loading it into SimCNC, but I find that the code was bad generated and could potentially lead to a machine crash (negative Z axis, some movements around + X and -X (third photo)

So, what's the expected behaviour from my point of view?

My 4th axis is mounted along my Y axis

My WCS (Work Coordinate System) is centered on the axis of rotation of the blank.

Because the design is a circular pattern around the circumference , I expect almost no movement around X axis (X0), and only rotating the B axis

The Z position should not be lower than Z12 (aprox)

What I think im getting?

After several attempts and some post-processor tweaking, that I think im getting is a code suitable for a machine with a tilting head, and no the workpiece.

What I tried?

I tried to edit the postprocessor to configure my machine, so code is generate for B axis (rotary axis along Y) with no luck.

I tried to put the stock 4 axis SimCNC postprocessor but I modified my CAM operations, for simulating that I have the fourth axis mount along X (as default) with no luck.

I tried post-processing the operation using the 4 axis Mach3Mill PP and I get that I want (a operation almost static in X axis and playing in YZA axis), but the output code is not compatible with SimCNC due to the Mach3/4 G93/G94 Gcodes usage

Has anyone here successfully created 4-axis G-code for SimCNC using Fusion 360?

Thanks in advance for any help!

Hello everyone,

I'm still experimenting with SimCNC, and now I'm working on 4-axis toolpaths. I'm using Fusion 360 (with the Machining Extension), but I haven’t been able to successfully generate G-code that works properly with my machine.

The test case is the following:

Im trying to cut a HTD-5M pulley from a 30.7mm aluminum blank. I modelled the pulley in Fusion360 and I'm going to cut it using a 3mm ball end mill. (See first photo)

The cutting strategy I used for this operation is a multi-axis rotary contour. (See the second photo for the generated trajectory)

Now, im loading it into SimCNC, but I find that the code was bad generated and could potentially lead to a machine crash (negative Z axis, some movements around + X and -X (third photo)

So, what's the expected behaviour from my point of view?

My 4th axis is mounted along my Y axis
My WCS (Work Coordinate System) is centered on the axis of rotation of the blank.
Because the design is a circular pattern around the circumference , I expect almost no movement around X axis (X0), and only rotating the B axis
The Z position should not be lower than Z12 (aprox)

What I think im getting?

After several attempts and some post-processor tweaking, that I think im getting is a code suitable for a machine with a tilting head, and no the workpiece.

What I tried?

I tried to edit the postprocessor to configure my machine, so code is generate for B axis (rotary axis along Y) with no luck.
I tried to put the stock 4 axis SimCNC postprocessor but I modified my CAM operations, for simulating that I have the fourth axis mount along X (as default) with no luck.
I tried post-processing the operation using the 4 axis Mach3Mill PP and I get that I want (a operation almost static in X axis and playing in YZA axis), but the output code is not compatible with SimCNC due to the Mach3/4 G93/G94 Gcodes usage

Has anyone here successfully created 4-axis G-code for SimCNC using Fusion 360?

Thanks in advance for any help!

Uploaded files:

#2 · 12 June 2025, 08:24

We've already received a support request regarding the 4-axis post-processor for Fusion. It does indeed generate toolpaths for a tilting head, regardless of the machine kinematics configuration set in Fusion. We need to investigate this more closely, and we believe the best solution will be to create a custom Fusion post-processor from scratch to ensure maximum reliability.

In the meantime, you can try the attached slightly modified Mach3 post. One of our customers is currently testing it, and we've received feedback that it's working well. However, please note that this is only a temporary workaround, so use it with extra caution. You can define machine kinematics with A axis on table or set rotary axis orientation in the post processor options.