G52 Rapid Positioning Problem

[cameraman]

Hello,  I've got a problem that maybe someone can shed some light on.  Sometimes after issuing a G52 offset for X and Y, if I don't immediately issue a X or Y command, the next rapid position acts as if it were in Incrimental and not Absolute positioning mode.  I'm in Absolute.

If you plug the following code into Mach3 then you'll see that it rapid positions way to the right, and then back before entering the subroutine the first time.  However, if you remove the line in the subroutine "G00 Z.125 % Remove this line" then it acts fine.  I always like to have that safe z positioning in there, just in case I forgot somewhere else.  This has been a problem for a while, if anyone knows a fix for it then please let me know.  Perhaps I need to change some settings.

Thanks,
   Stewart

G90
G52 x0 y0

% Contour Outside
F10
G00 X6.75 Y-.020
G00 Z-.125
G01 X7 Y0
G03 X7.5 Y.5 R.5
G01 Y4
G03 X7 Y4.5 R.5
G01 X6.75 Y4.520
G00 Z.125

%Countersink holes

G52 X7 Y.75
M98 P100

G52 X7 Y1.75
M98 P100

G52 X7 Y2.75
M98 P100

G52 X7 Y3.75
M98 P100

G52 X0 Y0

M02  % end program


O100 % SUBROUTINE bore hole .630 diameter, .375" deep
  G00 Z.125 % Remove this line
  G00 X0 Y0
  G00 Z-.125
  F3 G01 Z-.25
  F6
  G02 X.057 Y0 R.0285
  G02 X.057 Y0 I0 J0
  G02 X0 Y0 R.0285
  F3 G01 Z-.375
  F6
  G02 X.065 Y0 R.0325
  G02 X.065 Y0 I0 J0
  G02 X0 Y0 R.0325
  G00 Z.125
M99

M0

[Graham Waterworth]

the % sign in Mach depicts the start and end of the nc program, if you are running the program with these in the try removing them.

Graham.


%
G90
G52 x0 y0

(Contour Outside)
F10
G00 X6.75 Y-.020
G00 Z-.125
G01 X7 Y0
G03 X7.5 Y.5 R.5
G01 Y4
G03 X7 Y4.5 R.5
G01 X6.75 Y4.520
G00 Z.125

(Countersink holes)

G52 X7 Y.75
M98 P100

G52 X7 Y1.75
M98 P100

G52 X7 Y2.75
M98 P100

G52 X7 Y3.75
M98 P100

G52 X0 Y0

M30   (end program)

O100 (SUBROUTINE bore hole .630 diameter, .375" deep)
  G00 Z.125 (Remove this line)
  G00 X0 Y0
  G00 Z-.125
  F3 G01 Z-.25
  F6
  G02 X.057 Y0 R.0285
  G02 X.057 Y0 I0 J0
  G02 X0 Y0 R.0285
  F3 G01 Z-.375
  F6
  G02 X.065 Y0 R.0325
  G02 X.065 Y0 I0 J0
  G02 X0 Y0 R.0325
  G00 Z.125
M99
%

[cameraman]

Well I tried that, thanks for the tip, but it didn't make any difference.  In the manual, section 10.5.5 it says that a line that starts with a % is treated as a comment and not interpreted.  Perhaps that isn't true.

Thanks,
   Stewart

[cameraman]

If you stick the code in Mach3 and look at the tool path, then remove that one line in the subroutine (G00 Z.125) then you'll see the difference that it makes.  Attached are some screen grabs to show whats going on.  Removing that one rapid Z command makes it work correctly.

[Graham Waterworth]

It looks like an initialisation of the datum change that is causing the problem, if you swap the sequence around its fine.  I will pass this one on to Brian for his comments.

Graham.
 
%
G90
G52 x0 y0

(Contour Outside)
F10
G00 X6.75 Y-.020
G00 Z-.125
G01 X7 Y0
G03 X7.5 Y.5 R.5
G01 Y4
G03 X7 Y4.5 R.5
G01 X6.75 Y4.520
G00 Z.125

(Countersink holes)

G52 X7 Y.75
M98 P100

G52 X7 Y1.75
M98 P100

G52 X7 Y2.75
M98 P100

G52 X7 Y3.75
M98 P100

G52 X0 Y0

M30   (end program)

O100 (SUBROUTINE bore hole .630 diameter, .375" deep)
  G00 x0 y0
  Z.125
  G00 Z-.125
  F3 G01 Z-.25
  F6
  G02 X.057 Y0 R.0285
  G02 X.057 Y0 I0 J0
  G02 X0 Y0 R.0285
  F3 G01 Z-.375
  F6
  G02 X.065 Y0 R.0325
  G02 X.065 Y0 I0 J0
  G02 X0 Y0 R.0325
  G00 Z.125
M99
%

[cameraman]

Cool, thanks for passing it on, most of the time it is easy to change around the order but in some situations it has been difficult, and it is always good practice to have that safety Z move first in case I start a program from somewhere in the middle when it isn't already at a safe height.

Stewart