error

Discuss Thermwood 3-axis Machinery, Controller, and Software.

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Josh Rayburn
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error

Postby Josh Rayburn » Thu, Jul 21 2016, 2:12PM

CN export attached
please compare photo to the dxf files
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error.zip
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Josh Rayburn
Hall's Edge, Inc.
CNC Machining Service


Dell Precision T3400
Win7 Professional 64 Bit/Core2Duo E8400 3ghz/4 GB Ram/NVIDIA Quadro FX570

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Brad McIntosh
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Re: error

Postby Brad McIntosh » Fri, Jul 22 2016, 10:12AM

Josh,

Your issue is because of the lack of arc intersections when cutter compensation is applied. See the images to review the issue and the fix.

Issue-No Intersections.jpg


DXF-Fix.jpg


If there are any questions, let me know.


Regards,

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Brad McIntosh
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Re: error

Postby Brad McIntosh » Tue, Jul 26 2016, 7:52AM

Josh,

Was just wondering if my reply to your post helped to resolve your issue...

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Josh Rayburn
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Re: error

Postby Josh Rayburn » Thu, Jul 28 2016, 6:50AM

Hi Brad,
Sorry I haven't checked in for a little bit.
I understand the geometric issue, but can't figure out why the router cut two of the "clover leaves" successfully, yet the third one was incorrect.
I would have thought that the controller would simply fail to compensate - but it didn't - and it produced an unexpected result.
Not sure if it can be (or should be) "error-trapped" or not.
All the best,
JNR
Josh Rayburn
Hall's Edge, Inc.
CNC Machining Service


Dell Precision T3400
Win7 Professional 64 Bit/Core2Duo E8400 3ghz/4 GB Ram/NVIDIA Quadro FX570

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Brad McIntosh
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Re: error

Postby Brad McIntosh » Thu, Jul 28 2016, 10:06AM

Josh...

Why two out of three worked (or appeared to work -

Depending on the direction, the first "lobe" was starting out on the correct spot since the straight line and the first arc had an actual intersection during the compensation calculations. Therefore the INCREMENTAL ARC CENTER (defined by the IJ coordinates) correctly defined and "sized" the 1st arc/lobe.

The only thing is, is that since the first arc and second arc did not have an actual intersection in the calculated compensated path, the tool was NOT at the correct starting point for the next arc/lobe. So the INCREMENTAL ARC CENTER, defined an incorrect radius and center point for the next arc/lobe.

Now it appears that since this "wonky" 2nd arc was larger and off center, the resultant calculated compensated path at its endpoint did then produce an intersection with the 3rd "lobe" and therefore that final arc had the correct starting point - resulting in a correctly positioned INCREMENTAL ARC CENTER and properly positioned & sized "lobe".

==============

In today's day of CAD/CAM packages, this situation is usually avoided as the CAM side would either alert one to the issue in advance OR add something to correct it and provide a continuous path.

I would believe that Thermwood's "tolerance" with these non-intersecting entities during cutter compensation is so that in general, when dealing with instances with lots of small line and arc segments, that a small gap would be "smudged" through. (Just a guess though.)

Hopefully my fix got your parts cut...

Regards,

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Josh Rayburn
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Re: error

Postby Josh Rayburn » Fri, Jul 29 2016, 7:37AM

Hi Brad,
Thanks for the explanation, that was really helpful!
I ended up offsetting lines in CAD and running this with "centerline" operations.
That's my usual fix...I found overall that CN is completely unpredictable with "chain compin" operations and I haven't trusted them in years.
Thank you!
Josh Rayburn
Hall's Edge, Inc.
CNC Machining Service


Dell Precision T3400
Win7 Professional 64 Bit/Core2Duo E8400 3ghz/4 GB Ram/NVIDIA Quadro FX570


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