Problem- Mixing G2 & G3

[jtlodi]

I have 3 cnc software programs that are mixing of G2 & G3 codes one right after the other. Something like this ...

N10 G1 X4.0127 Y1.0288 Z-0.0960
N20 G2 X4.5926 Y0.3807 I-0.1655 J-0.7315
N30 G2 X4.4063 Y0.1723 I-0.1863 J-0.0208
N40 G1 X4.2170 Y0.1723 Z-0.0960
N50 G2 X4.0321 Y0.3286 I0.0000 J0.1875
N60 G3 X3.6606 Y0.3152 I-0.1849 J-0.0312
N70 G1 X3.6591 Y0.2264 Z-0.0960
N80 G2 X3.4716 Y0.0420 I-0.1875 J0.0031

I understand that G1 = Linear Interpolation and that G2 & G3 are circular interpolation moves ... G2 = clockwise ... G3 = counter clockwise.

Can someone explain why the cnc creation software would decide to use G2 verses G3?

I'm trying to understand the logic.

Thanks,

jtlodi

[PinMan]

are you attempting conventional milling or climb milling?

A lot of the time it might switch up to stay with the same type of milling. It also depends on the geometry.

Originally Posted by jtlodi N10 G1 X4.0127 Y1.0288 Z-0.0960 N20 G2 X4.5926 Y0.3807 I-0.1655 J-0.7315 N30 G2 X4.4063 Y0.1723 I-0.1863 J-0.0208 N40 G1 X4.2170 Y0.1723 Z-0.0960 N50 G2 X4.0321 Y0.3286 I0.0000 J0.1875 N60 G3 X3.6606 Y0.3152 I-0.1849 J-0.0312 N70 G1 X3.6591 Y0.2264 Z-0.0960 N80 G2 X3.4716 Y0.0420 I-0.1875 J0.0031

In your particular case here... it looks like the geometry is the reason.
In most all of the CAM softwares that I have used, how you pick the geometry for the toolpath affects the toolpath, i.e - if I draw a simple arc and click on the top of the arc when setting my geometry, it will climb mill (G02). If I click on the bottom of the arc, it will conventional mill (G03).

[beege]

It's the contour your milling. if you follow the contour in the direction of the cut, some of the curves are going to be convex, some concave. G2 and G3 are one or the other. G2 can't be both, neither can G3. Open the following attachment -



Follow the curves (generated from your data) with your finger, from top to bottom. One of them goes counter-clockwise, next to last curve. That was because of the G3 line. Hope this helps.

By the way, climb or conventional doesn't come in to play here, because its just a contour at this point

[jtlodi]

Thanks for putting this into simple english for me. In other words, the interpolation method used, be it G2 (CW) or G3 (CCW) is determined by the geometry and whether conventional or climb milling is chosen.

Thanks for helping me understand this.

[beege]

I repeat! Conventional or Climb has NO part in this! The direction you take along the contour geometry is the factor. The same geometry profile in the same direction could be climb milling or conventional, depending on where the stock is. If you are cutting a shaped groove with material on both sides, the cutter is cutting in BOTH conventional and climb at once. If the contour and direction in a pocket is climb milling; keep the contour and direction and make it an outside contour, and now you have conventional milling. G02 and G03 only describe the geometry, not the milling method.

[ssoptical]

the software that i use depends on how you chain / or choose the geometry
you select .
then if you can simulate the part before you post the nc code it will greatly
reduce any errors.
david.