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radius different one corner of square?
« on: March 27, 2012, 08:17:39 PM »
Hi,
this is my first time with a cnc machine and just had my first project completed.
I made simple pocket shapes (square, triangle, rectangle), each with a corner radius of 1/4"
The problem is where the toolpath starts for each shape.
The 1/4" bit starts in the corner and that radius is smaller than the rest for each shape.
What's the best way to alter the toolpath to have start in the middle of each pocket shape?

Are there any reference books, etc. that people can point me too?
I'm running Mach3, Vcarve and Autocad.

thanks a lot
David
Re: radius different one corner of square?
« Reply #1 on: March 27, 2012, 08:24:58 PM »
Correction,
It turns out the problem is not with the entry point, but with the other 3 corners of the square.
The radius on those seems to be twice as big as desired.
Not sure how to fix this, help appreciated.

Offline ger21

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Re: radius different one corner of square?
« Reply #2 on: March 27, 2012, 08:57:05 PM »
CV mode is causing the other corners to get rounded. The best solution is to  increase acceleration. You can also try playing with the different CV settings.

To chenge the start point in V-Carve Pro.
Switch to Node edit mode. If there's an existing point that you want to make the Start point, hold the cursor over it and hit "p", and it will turn green.
If you want to create a new Start Point, hold the cursor over the spot, and hit "i" to insert a point, then "p" to make it the start.
These options are also available from the right click menu.
Gerry

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

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: radius different one corner of square?
« Reply #3 on: March 27, 2012, 09:01:41 PM »
Not sure what CV mode is.
I just adjusted my drawing with no fillets, just hard corners and it did the same thing.
I'm using the pin settings that Romaxx recommended, not very confident to start messing with them yet.

Does this change your answer any?
thanks

Offline ger21

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Re: radius different one corner of square?
« Reply #4 on: March 27, 2012, 09:30:18 PM »
No.
CV mode is constant velocity mode.
Mach3 tries to maintain constant velocity, which means when it gets to a corner, one axis needs to start moving before the previous one stops.
In General Config, try setting the "Stop CV on angles" setting to 89 or 90.
Gerry

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

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: radius different one corner of square?
« Reply #5 on: March 27, 2012, 11:10:00 PM »
Thanks a lot Gerry, will give this a try.