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Author Topic: Arc's in planes other than G17  (Read 3629 times)

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Arc's in planes other than G17
« on: March 22, 2010, 05:54:28 PM »
Trying to program a helix in G18 (which would be XZ plane, axis of arc parallel to Y axis).  An example of the code would be:

G00 X0.375 Y0. Z0.375
G18
G02 X0. Y0. Z0. I-0.375 F10.

IJK is set to incremental, and I do get an arc on the toolpath display.  However there is no difference shown between G02 and G03. Both would generate what would be a CCW arc.  Now it's entirely possible that I missed something stupid, and I did try multiple computers with multiple profiles and the issue repeats itself.  Although I mentioned cutting a helix, which is the end goal, I have cut back the code to just get an arc to cut.  I also tried with R values. 
I know arcs (let alone helix's) in planes other than G17 aren't that common so maybe this hasn't come up before.

Offline ger21

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Re: Arc's in planes other than G17
« Reply #1 on: March 22, 2010, 09:28:15 PM »
Looks like a bug in the display. But if you run the code, it runs correctly. The G3 will travel in the gap of the displayed arc.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

Offline ger21

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Re: Arc's in planes other than G17
« Reply #2 on: March 22, 2010, 09:31:25 PM »
Btw, I have cut G18 arcs before and they were displayed correctly, but I found another bug at the time. The feedrate of the G18 arc was limited to the Z axis velocity in motor tuning. I reported it to Brian, but don't know if it ever got fixed.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Arc's in planes other than G17
« Reply #3 on: March 22, 2010, 09:33:57 PM »
I am unwilling to run code that won't display, just doesn't seem like a way to be able to check yourself.  Does not instill me with confidence.  I think it may be time to move on to other software options..

Offline ger21

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Re: Arc's in planes other than G17
« Reply #4 on: March 22, 2010, 10:23:02 PM »
I reported it on the Yahoo group.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

Offline RICH

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Re: Arc's in planes other than G17
« Reply #5 on: March 22, 2010, 10:27:19 PM »
You may want to take a look at Mach3 Turn Arc motion write up which can be found in the Members Docs as it goes
into a lot of detail and explaination about arcs for the lathe which uses G18.

As far as cutting a helix as a continous motion, i have done that using an indexer. In a sense you can cut a helix using
a threading code. Some of the wrapping programs provide code but it breaks the helix into small straight line segments.

FWIW,
RICH  
Re: Arc's in planes other than G17
« Reply #6 on: March 23, 2010, 11:05:29 AM »
There really is no other way to run the code I need to run other than to just get the machine to run as it's documentation suggests. Additionally to the above requirements I need to make a move in the A axis while the helix is going on.  For testing purposes I have removed the A axis moves to just try and generate a correct arc (to no avail).  While it *may* run the code but display it wrong, it doesn't help me to think that it might at some point display correctly and not cut correctly or any one of a number of bizarre scenarios. 
Pretty much the final nail in the coffin for me, time to look elsewhere for reliable software...

Offline RICH

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Re: Arc's in planes other than G17
« Reply #7 on: March 23, 2010, 12:19:37 PM »
I wish you luck in your search for alternative software and programing endeavors.

RICH