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PS0041 Interference in G41/G42?

Eric U

Hot Rolled
Feb 26, 2003
Eastern AL
I've got this error and can't figure out why? New to Fanuc, and for that matter, cutter comp. Doosan Lynx. This program is supposed to cut a stepped bore, starting with a chamfer of .020" leading to an initial diameter of 1.002". Then the bore steps to #1 below, with a .010" chamfer between steps.

#500=.974 (diameter of part that needs to fit into this bore, set in main program)
#1=#500+.005 (giving the bore .005" of fit clearance)

G00 G40 G80
T0808 (1/2" boring bar, .0156" TNR)
M34 G99
G50 S3000
G54 G96 M3 P11 S750
G00 X2. Z1.
G41 G00 X.75 Z.1
G71 U.075 R.05
G71 P150 Q220 U-.01 W.01 F.0075
N150 G00 X1.042
N160 G01 Z0. F.003
N170 X1.002 Z-.02
N180 Z-1.
N190 X[#1+.02]
N200 X#1 Z-1.01
N210 Z-2.25
N220 X.75
G70 P150 Q220
G40 G00 Z1.

Any hints would be great. I've tried other sizes of #500 and they worked fine. There is a "changeover" in what the profile looks like when X GE .978.

Thank you,
Eric U
PS0041 Overcutting will occur in tool nose radius compensation. Modify the program.

I am not a macro guy but I think it is puking line N190 its only dropping down .003 before it starts the next chamfer. Sometimes comp will aggravate the hell out of me. I may be wrong but my money is on line N190. Remove it and see if it runs.

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Hello Eric,
Brent's suggestion in Post #2 is correct when there is a 45deg move, as is the case in you example, following Block N190. The radial move from the previous diameter to X[#1+.02] is only 0.0015". With the 45deg angle move that follows, the smallest this move can be is 0.00914 when using a 0.0156 tool nose radius. In fact this will probably still raise an interference error, as Facuc controls generally need clearance of the Least Programmable Increment in TNR comp calcuations. Accordingly, 0.0092 would probably be the minimum move in the case of your program.

If the Block following N190 was parallel to the Z axis, then the control will accept the N190 move as there will be no Interference. The Interference is caused by the control needing to position the TNR tangent to the surface described by N190 (perpendicular to the Z axis) and the angled surface described by the N200 block. The position of the TNR to achieve this tangency will result in interference with the X1.002 diameter.

It would seem that you have a constant diameter of X1.002 included in your profile description. If you wanted to make the program more bullet proof, you could carry out a calculation shortly after the Macro Variables are set to determine if the N190 Block move is less than 0.0092 (radial value). If yes, the N190 Block could be skipped. In this case, there would be further calculations required to find the start of the angled surface, based on its specified end point (not difficult).


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