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Author Topic: Jerky transition between inline arc movements  (Read 1924 times)

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Offline rh

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Jerky transition between inline arc movements
« on: October 29, 2011, 04:22:44 PM »
Hi,
I fairly new to Mach3 (but well versed in shopbot)
I have played around with CV settings, but cannot get my cnc to transition smoothly between arced paths that meet straight lines and each other in line using G02 commands in a tool path file. I have cv on with distance set to 2(mm), and find I need this to stop arcs forming around any angular change in direction (with a bit 4mm dia and over). The machine slows up like it were going round a sharp corner - but it isnt, but not on every transition.
The following code does it around 4 times, though it is cutting a single large circle:

(Start of cutpath 11102921.01)
G21
G00 Z25

(Path 1)

G00 X309.93 Y332.19
G01 X309.93 Y332.19 Z0.00 F1000
G02 X309.93 Y212.01 I-184.93 J-60.09 F3000
G02 X239.29 Y114.79 I-184.93 J60.09 F3000
G02 X125.00 Y77.65 I-114.29 J157.31 F3000
G02 X10.71 Y114.79 I0.00 J194.45 F3000
G02 X-59.93 Y212.01 I114.29 J157.31 F3000
G02 X-59.93 Y332.19 I184.93 J60.09 F3000
G02 X10.71 Y429.41 I184.93 J-60.09 F3000
G02 X125.00 Y466.55 I114.29 J-157.31 F3000
G02 X239.29 Y429.41 I0.00 J-194.45 F3000
G02 X309.93 Y332.19 I-114.29 J-157.31 F3000
G00 Z25
G00 Z25
G00 X0 Y0
M30
(End of File)

Any help most appreciated.

Ralph.
Re: Jerky transition between inline arc movements
« Reply #1 on: October 30, 2011, 06:42:43 PM »
I have only been doing this for a year so I'm new as well. But I ran into the exact thing last week. It turned out to be Sketckup in my case. When I made the drawing and import to CamBam, the arcs were not one section but instead were many. When I dry cycled it through the program, my servos looked like they were having a fit around the corners.  exploded the drawing and noticed the many sections. I redid the corners in CamBam from scratch and it was fine after that.

Hope this helps
Re: Jerky transition between inline arc movements
« Reply #2 on: October 30, 2011, 09:01:52 PM »
It also has something to do with the size of the arc.  I've always seen this on small (like 1/2" diameter or less) arcs.  Where the arc meets a straight line segment, mach hesitates.  I see it all the time cutting small slots.  Make the slot larger and the problem goes away.  To complicate things even further, it doesn't do it all the time.  I can make one slot in Rhino and duplicate it 10 times in Sheetcam.  Some of the slots will hesitate and some won't.