Radius compensation

[Morfeus80]

Dear all,
I am trying to use the diameter compensation G41/G42 to make an hole, but I am facing several problems.
I tried several G-codes but I am not able to get the wanted result. This is an example of one code:

Code: Select all

%
O1000
( ********************************************************************** )
( *    INTELLIGENT MANUFACTORY SOFTWARE WWW.IMS-SOFTWARE.COM           * )
( *    IMSPOST VERSION : 7.4R                                          * )
( *    USER VERSION : 1                                                * )
( ********************************************************************** )
N1 G49 G64 G17 G80 G0 G90 G40 G99
( IMSPPCC_MILL PPTABLE 06-13-2003 )
( END MILL D6 RC0 )
N2 T1003 M6
N3 X10. Y-10. S21242 M3
N4 G43 Z35. H1
N5 G1 G94 Y0 F300.
N6 X0
N7 Z5.
N8 Z1.
N9 Z-10.
N10 G41 X.261 Y-1.39 D1
N11 G3 X1.651 Y-1.129 I.564 J.825
N12 X-1.996 Y.126 I-1.651 J1.129
N13 X1.651 Y1.129 I1.996 J-.126
N14 X.261 Y1.39 I-.826 J-.564
N15 G1 G40 X0 Y0
N16 Z1.
N17 Z11. F600.
N18 X-10.
N19 Y10.
N20 M5
N21 M30
N22 M2
N23 M30
%


And this is the resulting toolpath:

As you see, while the diameter is correct for D 6mm mill, the approach and the retract are weird.
The starngest thing is that the screenshot is stopped at after line N7 and in N6 the command was X0, instead if you look at actual coordinates X=3.20.
Why is this happening, still none compensation G-Code has been executed.

[ger21]

Don't have time to look to deep, but that appears to be a 4mm hole?

And the Lead In move is only about 1mm, and need to be greater than the tool radius.

I haven't checked lately, but the lead ins have never worked correctly with G41/G42, imo.

[Morfeus80]

Thanks for the answer. The hole is 10mm and the tool 6mm diameter. I have tried different approaches but the result doesn't change much.
And why is it stopping at 3.20 instead going to 0, even before any G41/42 is applied?

[cncdrive]

The problem is that the tool radius is less than the arc radius.

[Morfeus80]

Which arc is bigger than the tool radius?

[Morfeus80]

I have done quite a lot of tests and I have found somethin interesting.
This was the original code:

Code: Select all

N1 G49 G64 G17 G80 G0 G90 G40 G99
( IMSPPCC_MILL PPTABLE 06-13-2003 )
( END MILL D6 RC0 )
N2 T1003 M6
N3 X10. Y-10. S21242 M3
N4 G43 Z35. H1
N5 G1 G94 Y0 F300.
N6 X0
N9 Z-10.
N10 G41 X-1.433 Y-3.866 D1
N11 G3 X4.127 Y-2.823 I2.258 J3.301
N12 X-4.99 Y.316 I-4.127 J2.823
N13 X4.127 Y2.823 I4.99 J-.316
N14 X-1.433 Y3.866 I-3.302 J-2.258
N15 G1 G40 X0 Y0
N16 Z1.
N17 Z11. F600.
N18 X-10.
N19 Y10.
N20 M5
N21 M30
N22 M2
N23 M30


and I modify
- line N10 putting the G41 in the following line
- line N15 putting G40 in the previous line

Code: Select all

N1 G49 G64 G17 G80 G0 G90 G40 G99
( IMSPPCC_MILL PPTABLE 06-13-2003 )
( END MILL D6 RC0 )
N2 T1003 M6
N3 X10. Y-10. S21242 M3
N4 G43 Z35. H1
N5 G1 G94 Y0 F300.
N6 X0
N9 Z-10.
N10 X-1.433 Y-3.866
G41 D1
N11 G3 X4.127 Y-2.823 I2.258 J3.301
N12 X-4.99 Y.316 I-4.127 J2.823
N13 X4.127 Y2.823 I4.99 J-.316
N14 X-1.433 Y3.866 I-3.302 J-2.258
G40
N15 G1 X0 Y0
N16 Z1.
N17 Z11. F600.
N18 X-10.
N19 Y10.
N20 M5
N21 M30
N22 M2
N23 M30


Then the code works properly.
Why? The new syntax is not a "standard" one… Is it a problem in UCCNC?

[cncdrive]

Load it in mach3, it will give you an error that the arc radius is smaller than the tool radius and the code will not even load. So, no it is not a problem in the UCCNC, it is a problem in your code.

[Morfeus80]

Please, try to check the code, there is not any bigger radiys than the tool radius.
And also why modifying just the 2 lines as above it works? It looks like G41/42 are not applied from the line where they are, but from the previous command. Why?

[cncdrive]

G41/G42 offsets the path, to offset the path you need to go along the path, look ahead with one line, because when you have 2 lines for example then you can place the connection angle only when you know the placement of the second line.
So, while G41/G42 looks simple, as it is just simple offset you might think, in reality it is a very complicated algorithm.

And sorry, but I do not have time now to analyse your code now, but it is sure something wrong with it, because the UCCNC does not offset it properly and Mach3 does not even load it saying that the arc radius is smaller than the tool diameter.