Problem to understand what fusion360 post processor does

[dhuvelle]

lecorcevive.pro

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Hi everyone,
yesterday I machined a piece on my CNC. the piece is only splines. I knew it was going to be tricky because my machine is a greenbull V2 from buildyourCNC and it's not the most rigid machine ever created but it works fine, I'm making a lot of stuffs with it and I'm happy with it for now.

all that to explain that I started to tweak the CV settings without any changes or barely. Came on the forum and found some topic to help me understand that arcs are not impacted by CV settings (if I understood correctly, ... I hope so).
that I have read couple other things on autodesk forum and started to think that problem could come from the post or maybe Fusion itself.

first of all I'm not an expert at all.
In Fusion, I have download the last post processor and tried different settings in the built-in section of the process window to see what it was changing in the gcode. I used UCCNC in demo mode with my machine settings to simulate the job with those gcode. acceleration for my machine is pretty low X and Y at 370 and Z I don't remember but this one is not subject to rigidity issues.

I've understand that leads in and out are using G1, ok that's fine I don't think it could be a problem for me. CV settings in UCCNC are smoothing it. OK
the problem I found in my gcode is that the majority of the splines are G2 and G3 but sometimes some arcs are transformed in G1 instead of G2 or G3. my setting in fusion for the minimum chord length is 0.001 and minimum circular radius is also 0.001 (I guess mm because documents units are in mm for me) tolerance for linearization is 0.01 mm. helical moves are OFF (I think it's only for the lead in and out, ramp , etc ...) smoothing is OFF too. tolerances in the toolpaths are set to 0.1mm as default for me (not sending stuffs in to space and i'm working with wood so it seems good for me)

Gcode is here ,https://www.transfernow.net/dl/20211009YwwVjtzK

does anyone have an idea about what is going on ? had the same problem and found a solution ?

thank you guys, can't wait to see your replies under this post at least I hope so )

[cncdrive]

Your explanation is very nice and detailed, but you forgot to tell us what the problem is?

[dhuvelle]

You are right, I was in the rush with my kids and I forgot the most important part

Problem is that it cause the machine to slowdown and to make jerky moves when those G1 are a lot and close to each other.
I also remarked that on pockets the last pass on the rims of the shape is only G1 moves … or suppose that it could be done with G2 and G3.

It also make facets on the rims what is not really wanted when machinning

[cncdrive]

Do you have or can you make some photos of the problematic parts?

[dhuvelle]

I’m not at the shop now so difficult to do some picture but I attached the gcode and my profile to this post.

I kept doing changes in the settings of fusion’s post processor for UCCNC. Searching what settings does what by changing values one at a time. I also changed the settings in the toolpath itself (tolerance of machining, smoothing deviation, minimum cutting radius) I finally found that using higher tolerance (0,05mm) instead of a smaller tolerance (0,001) was creating less small moves.

To keep it briefly, I tried to avoid really small moves in the toolpaths (cutting,leads, ramps, etc …).
When simulating the gcode in UCCNC it seems to be better, I have no more or at least less changes of the actual feed rate. I need to check that IRL tomorrow.

Does a lot of people use fusion 360 on the forum ? And do they had issues like me ?