Cone Icon moves off of part

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Cone Icon moves off of part

Postby markcadcam » Tue Dec 05, 2017 1:14 pm

When running the attached file at around Line 4420, the the cone icon moves off of the part to right and front side. I've ran it 3 times with the same results. I'm using version 1.2046. Not sure if this is a bug?
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Re: Cone Icon moves off of part

Postby cncdrive » Tue Dec 05, 2017 1:50 pm

No, it is not a bug.
The TCP cone moves off the path, because of the constant velocity optimisation (G64) and because of the CV settings.
In G64 mode the software will try to go through the path with trying to keep the programmed feedrate (often fast) which means the shortest paths mostly with the software keeping in mind what tolerances you setup,
which means that you allow the software to go off the path with a maximum path distance of the tolerance you setup.
So, for example if you setup a linear error of 0.1 and a corner error of 0.1 and you are in G64 mode then you allowed the software to go off the path with 0.1 units max.

Your g-code path dimensions are very small and so the default small tolerances which are set by default in the UCCNC can be significant for this particular job.
You can lower the tolerances, or switch to G61 exact stop mode, however with using G61 you basicly disabling the CV optimisation, so the software will have to deccelerate on all the programmed points, so probably it is a better idea to lower the tolerances and keep it in G64 mode for this particular g-code.

Another thing is that the drawing is very small and the TCP cone position points (coordinates) will be always the multiplication of the 1/steps per value,
because that is the resolution of your stepper or servo drives, so your axis can physically can make that as a smallest step, the axis can't step in between those.
I'm just mentioning this one, because your toolpath is really small and with a rough steps per value it can be even seen that the TCP cone is moving on the step around the path, where the machine can't step can be also seen with the default steps per settings. However ofcourse if this can be seen or is a problem at you depends on your steps per values.
To make an example, your home position is 0 and your steps per is 100, and so the resolution is 1/100 = 0.01. You want to command the axis to 0.005, then what happens is the axis can't move to that point, it can move to 0.00 or 0.01, because the steps per value defines the grid where the machine can move and the 0.005 is a midpoint between, it is a fraction point of the set resolution of the axis, so the machine and therefor the cone can't move to that exact point.
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Re: Cone Icon moves off of part

Postby markcadcam » Tue Dec 05, 2017 2:12 pm

Okay. Why is it only doing it at the very end of the program?
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Re: Cone Icon moves off of part

Postby cncdrive » Tue Dec 05, 2017 4:57 pm

No, it's not, it is doing it everywhere on the path.
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Re: Cone Icon moves off of part

Postby markcadcam » Tue Dec 05, 2017 5:15 pm

Are you looking at it in the ISO view? I forgot to mention that.
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Re: Cone Icon moves off of part

Postby cncdrive » Tue Dec 05, 2017 7:03 pm

I was looking at it one with the top view and second with rotating the top view a bit over to also see the height, I ran it twice, to see all axis movements and I ran through the whole code and watched it.

On the other hand which view is it does not really matters, it only influances what axes you visually see, but the cone is always drawn to the coordinate of the X and Y and Z DROs,
if the view is changed this does not change, what changes is only that the OpenGL viewpoint is changed, it is like the point of the camera is changed which camera is viewing the scene which is "your eyepoint",
which I think is easy to understand that it does not change the coordinate of the cone in the 3D viewspace, it just changes from which point the drawing scene is viewed from.
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Re: Cone Icon moves off of part

Postby markcadcam » Tue Dec 05, 2017 7:19 pm

Thank you.
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