CW_HELICAL_ARC_PLUNGE_MOVE

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M Queen
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CW_HELICAL_ARC_PLUNGE_MOVE

Post by M Queen »

Can someone please explain the difference between "CW_HELICAL_ARC_PLUNGE_MOVE" and "CW_HELICAL_ARC_MOVE"?

Thank you.
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Pete Cyr
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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by Pete Cyr »

I am no authority but I would presume from the nomenclature one involves movement is the Z axis and one does not

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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by M Queen »

Thanks Pete, but any helical arc does a plunge move. You're plunging (ramping) while doing an X, Y arc.
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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by Adrian »

As far as I understand it if you have the PLUNGE_MOVE section in the PP then the first move of the helical arc will be executed in that section. If it's not there (and for the subsequent moves) the ARC_MOVE will be executed.

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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by M Queen »

Thanks Adrian, but every time I try to use just the CW_HELICAL_ARC_PLUNGE_MOVE, I get straight G1 moves (no arcs). I'm setting WinCNC's post processors up for these arcs and I don't want any surprises. I'm just going to set it up with the CW_HELICAL_ARC_MOVE section. That works exactly as I would expect it to.
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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by gregk »

M Queen wrote:Can someone please explain the difference between "CW_HELICAL_ARC_PLUNGE_MOVE" and "CW_HELICAL_ARC_MOVE"?

Thank you.
Both indicate an arc with z-level change. The "CW_HELICAL_ARC_PLUNGE_MOVE" will use plunge feedrate (unless post-processor overrides it) while "CW_HELICAL_ARC_MOVE" will use cut feedrate.
When using spiral ramping, "CW_HELICAL_ARC_PLUNGE_MOVE" will be issued. However, if you use 3D tabs in the profile toolpath and place them on the arc, "CW_HELICAL_ARC_MOVE" will be issued.

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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by M Queen »

Thanks Greg. I did get it to work, but I wound up finding a bug, I think.
Image1.jpg
Have a look at that front tab. The rest are normal 2D tabs. When I generate this, I get all G3 (CCW) arcs except when I come to that. Then I get two G2 (CW) arcs that go completely back around my circle. Not split into 4 quadrants, just completely back around. The G2 (CW) arcs aren't the helical arcs, but regular arcs.

I can recreate it easily.
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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by gregk »

Could you post a file here so I can have a look into the issue?

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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by M Queen »

Here is the CRV3D file
Attachments
Error Arc.crv3d
(63.5 KiB) Downloaded 60 times
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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by M Queen »

Here i the tap file. I had to rename it to .txt but no other changes. I did comment on the end of the Plunge/No Plunge lines in the post processor though so I could see what was happening in the file.
Error Cut.txt
(2.3 KiB) Downloaded 67 times
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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by gregk »

Thanks Mike - I have looked into issue. It seems that numerical accuracy issues caused the vertical move before this particular tab to be reordered (you can see N57 G1 X2.767526 Y0.887755 Z0.090000 being at the very end, rather than before the tab).
It is possible that this issue also existed in v9, but back then all tabs were approximated with series of linear moves. So even if this reordering happened, you wouldn't notice it since spans were very short.

This issue will need some time to be fixed (definitely not in the next patch). In the meantime you could move the toolpath start point to e.g. the bottom left corner. Sorry for the inconvenience.

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Re: CW_HELICAL_ARC_PLUNGE_MOVE

Post by M Queen »

Hi Greg,

I started to leave your reply as the last word but I tried something else and it seems to work well with this. If you do 3D tabs, it seems to correct the issue. Of course there will probably be cases where 3D tabs are not going to work or the user doesn't want them, and in that case your solution might be the only working one for now other than leaving the tabs out completely.

Thank you for your assistance.
Attachments
Good Cut.txt
(2.05 KiB) Downloaded 56 times
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