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Josh Rayburn
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error

Post by Josh Rayburn »

CN export attached
please compare photo to the dxf files
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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
Brad McIntosh
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Re: error

Post by Brad McIntosh »

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,
Brad McIntosh
CNC Automation

Home: http://www.cncautomation.com
Twitter: @bmcncautomation
Brad McIntosh
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Posts: 559
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Re: error

Post by Brad McIntosh »

Josh,

Was just wondering if my reply to your post helped to resolve your issue...
Brad McIntosh
CNC Automation

Home: http://www.cncautomation.com
Twitter: @bmcncautomation
Josh Rayburn
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Re: error

Post by Josh Rayburn »

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
Brad McIntosh
Guru Member
Posts: 559
Joined: Wed, May 18 2005, 6:59PM
Company Name: CNC Automation
Country: CANADA
Location: St. Zotique, Québec, Canada
Contact:

Re: error

Post by Brad McIntosh »

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,
Brad McIntosh
CNC Automation

Home: http://www.cncautomation.com
Twitter: @bmcncautomation
Josh Rayburn
eCabinets Beta Tester
Posts: 1263
Joined: Wed, Jul 01 2009, 2:19PM
Company Name: Halls Edge Inc
Country: UNITED STATES
Location: Stamford, CT USA
Contact:

Re: error

Post by Josh Rayburn »

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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