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Lathe Gcode Arc Issue

Posted: Tue May 14, 2019 12:04 am
by tmday7
I have a Gcode that is getting an error that the Radius starting point differs from end point. I dont know what to change in my CAM to output a code that KMCNC lathe likes. I have tried Fanuc lathe and Haas Lathe post processor in Fusion360.
The Gcode roughs an OD with a radius at the beginning, then a finish pass. Tried just the finish pass and there was no issue.
Below is the entire program.
Any ideas what i need to change?


O1001 (1001)
N1 G98 G18
N2 G20
N5 G53 G0 X0.

(Rough OD)
N6 T1
N7 G98
N9 G97 S400 M4
N10 G54
N11 M8
N12 G0 X4.5 Z0.1
N13 G1 Z0.0978 F3.
N14 X4.335
N15 Z-2.7815
N16 X4.375
N17 G0 Z0.1
N18 X4.295
N19 G1 Z-2.7815 F3.
N20 X4.335
N21 G0 Z0.1
N22 X4.255
N23 G1 Z-2.7815 F3.
N24 X4.295
N25 G0 Z0.1
N26 X4.215
N27 G1 Z-2.7815 F3.
N28 X4.255
N29 G0 Z0.1
N30 X4.175
N31 G1 Z-2.7815 F3.
N32 X4.215
N33 G0 Z0.1
N34 X4.135
N35 G1 Z-2.7815 F3.
N36 X4.175
N37 G0 Z0.1
N38 X4.095
N39 G1 Z-0.1286 F3.
N40 G18 G3 X4.1 Z-0.1565 I-0.154 K-0.0279
N41 G1 Z-2.7815
N42 X4.135
N43 G0 Z0.1
N44 X4.055
N45 G1 Z-0.0756 F3.
N46 G3 X4.1 Z-0.1565 I-0.134 K-0.0808
N47 G1 X4.26
N48 G0 Z0.1
N49 X4.015
N50 G1 Z-0.0493 F3.
N51 G3 X4.075 Z-0.0952 I-0.114 K-0.1072
N52 G0 Z0.1
N53 X3.975
N54 G1 Z-0.0314 F3.
N55 G3 X4.035 Z-0.061 I-0.094 K-0.1251
N56 G0 Z0.1
N57 X3.935
N58 G1 Z-0.0186 F3.
N59 G3 X3.995 Z-0.0396 I-0.074 K-0.1379
N60 G0 Z0.1
N61 X3.895
N62 G1 Z-0.0096 F3.
N63 G3 X3.955 Z-0.0245 I-0.054 K-0.1469
N64 G0 Z0.1
N65 X3.855
N66 G1 Z-0.0037 F3.
N67 G3 X3.915 Z-0.0137 I-0.034 K-0.1528
N68 G0 Z0.1
N69 X3.815
N70 G1 Z-0.0006 F3.
N71 G3 X3.875 Z-0.0063 I-0.014 K-0.1559
N72 G0 Z0.1
N73 X3.775
N74 G1 Z0. F3.
N75 X3.787
N76 G3 X3.835 Z-0.0019 K-0.1565
N77 G0 Z0.1
N78 X3.735
N79 G1 Z0. F3.
N80 X3.787
N81 X3.795 Z-0.0001
N82 G0 Z0.1
N83 X3.695
N84 G1 Z0. F3.
N85 X3.755
N86 G0 Z0.1
N87 X3.66
N88 G1 Z0. F3.
N89 X3.715
N90 G0 Z0.1
N91 X3.625
N92 G1 Z0. F3.
N93 X3.68
N94 X4.1415
N95 G0 X4.5
N96 Z0.1

N97 G1 X4.5 Z0.1 F100.
N98 G0 Z0.08
N99 X4.0734
N100 G1 X3.5612 F3.
N101 Z0.
N102 X3.787
N103 G3 X4.1 Z-0.1565 K-0.1565
N104 G1 Z-2.7815
N105 X4.2131 Z-2.7249
N106 X4.26
N107 G0 X4.5
N108 Z0.1

N109 M9
N110 G53 X0.
N111 G53 Z0.
N112 M30

Re: Lathe Gcode Arc Issue

Posted: Tue May 14, 2019 12:19 am
by tmday7
Think i got it. I changed the post processor to output Radius Arcs instead of I,J,K. KMCNC preview looks good with no errors.

Re: Lathe Gcode Arc Issue

Posted: Tue May 14, 2019 2:51 am
by TomKerekes
Strange. Lines:

N44 X4.055
N45 G1 Z-0.0756 F3.
N46 G3 X4.1 Z-0.1565 I-0.134 K-0.0808

have a 0.022524 inch difference in radii

You might also try the Fusion post processors here.