Toolpath precision issues from fusion 360

[GeoffreyP]

Hi everyone !

I have bought a Workbee CNC machine from the company Ooznest and I'm trying to calibrate the machine.
I'm using Fusion 360 and it seems that I have a toolpath issue but I don’t know if it’s a machine issue or a software one but all of my outliner cut are correct but not the one which go in.

So i have drawn a square of 62 by 62mm with a notch of 18mm (please see attached picture 1-1 & 1-2).
To make this work, I have mounted on the CNC a flat 1/4 inch end mill from your starter kit (please see attached picture 5-1 & 5-2).
On fusion 360, I have set up some parameters to do the job ( please see attached picture 2-1 until 4).

By the end, after doing the first test, I have got :
x=62,76 mm instead of 62 (picture 6-1)
y=62,49 mm instead of 62 (picture 6-2)
notch= 17,18 instead of 18 (picture 6-3)

I have watched the ooznest video about how to calibrate the workbee, I have done it 3 times to have a precise cut ( picture 7).
Link :

After doing the last cut, I have got :
x=62,00 mm instead of 62 (picture 8-1)
y=61,98 mm instead of 62 (picture 8-2)
notch= 17,12 instead of 18 (picture 6-3)

I don’t understand why my outliner cut are correct and not my interline cut, it doesn’t make sens to me.
To give you more details, I have downloaded your small program for fusion and to export the gcode.
Hope you have enough element to find out my problem and tell me what’s going on and hopefully give me a solution.

You will see the rest of the image on the next post.
Thank you all in advance

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[GeoffreyP]

Please see attached the next pictures

[GeoffreyP]

If you need more details, please let me know

Thanks

[ger21]

Try changing the cut direction, and see if the results are different.

I'm guessing that flex in the machine is causing the discrepancies.

[GeoffreyP]

Try changing the cut direction, and see if the results are different.

I'm guessing that flex in the machine is causing the discrepancies.

Thanks ger21 for your reply, I will try when I will be in the workshop and let you know then.

[GeoffreyP]

I have done the test tooday at the workshop and I the result is quite similar but on the other way around !
Instead having 17.12 from climb milling (left), I have got 18.70 from conventional milling (right)...

Any other suggestions ?

[ger21]

So you're seeing a 1.5mm difference between climb and conventional? This is almost certainly machine flex.

I'd try climb cutting 1mm oversize, then do a finish pass conventional cutting, at a slightly slower feedrate.

[GeoffreyP]

So you're seeing a 1.5mm difference between climb and conventional? This is almost certainly machine flex.

I'd try climb cutting 1mm oversize, then do a finish pass conventional cutting, at a slightly slower feedrate.

The weird thing is I have 62 mm on each side (same than the climb milling), only the internal measure is different ...
A lot of people told me that it might be the software Fusion 360 because some issue of the toolpath but I have done the same test witht the software Vectric and it's worst !

What do you mean by machine flex ? like flexible about the setting or not strong enough ? I have a workbee machine, should be fine for wood in theorie

[ger21]

What do you mean by machine flex ? like flexible about the setting or not strong enough ? I have a workbee machine, should be fine for wood in theorie

Not stiff enough. That's a very lightweight machine, and probably flexes fairly easily.

I use a $150,000 machine that weighs 10,000 lbs, and it will flex when cutting wood.

Try doing a rouging pass like I mentioned, and see if it helps.

A lot of people told me that it might be the software

These people don't know what they are talking about. People are always asking if their problems are due to their software. They almost never are.