G55 work offset 1st cycle off???

[Roger]

Today I ran a program on a Mori Mill, I loaded the proven program, the part has been done many times before, and the work offsets (G55, G56) are recorded on the back of the print. So I input them, The part is a pre-manafactured fiberglass box done in a Hass rotary, (I cut a retangular cutout in the top, and two small holes in one side.

 

Pushed cycle start, it looked like everything was good. I measured the width and diameters of the cutouts, (needed to offset the tool -.005 to get the right sizes. I pushed cycle start (This time the toolpath in the top of the box ran out about a 1/4" in the Y axis, the tolpath on the side the box ran the same.

 

I had 20 parts to run. After that 1st part everything was good??? Any ideas why the 1st cycle cut 1/4" off. (I changed nothing!!!)

[john316]

.

 

Maybe something active that was cancelled at the eop?

 

.

[Guest CNC Apps Guy 1]

Usually this is because the correct offset is not activated. I always have safety lines making sure everytihg that I don't wan on is deactivated and everythign I want on is activated.

[chris m]

I have experienced some issues with Fanuc 18s (most, if not all, newer Mori mills are Fanuc) where the machine will not correctly position if G90 is not the same line as the WOFS call. I understand that G90 is modal, but I have seen this with my own eyes. Force a G90 in the same line as the WOFS call and see if the problem is eliminated:

 

G90 G54.1 P3 X-2.3906 Y1.2203 S1485 M03 T03

[Roger]

Here is the start to the program. (As you can see I have a safety line,and G90 on the same line as the work offset), also I said only the Y axis was offset on the 2nd cycle start. The width and length of the cutout was small by .005 after the 1st cycle, So the only thing that changed was the wear offset by that amount. It's as though the machine was off by 1/4" in Y on the 1st cycle.

 

Anymore Ideas? This doesn't make sense!

 

%

O0007(19001610 REV 2)

G20

G0G17G40G49G80G90

T8( 1/4 FLAT ENDMILL)

M6

G0G90G55X4.3156Y-2.434S4500M3

G43H8Z.25

Z.1(CUT SQ CUTOUT IN TOP)

G1Z-.25F25.

G41D28Y-2.409F32.

G3X4.2656Y-2.359R.05

G1X.885

Y-5.3703

X7.6463

Y-2.359

X4.2656

X4.2356

G3X4.1856Y-2.409R.05

G1G40Y-2.434

X4.3156Y-2.424

G41D28Y-2.399

G3X4.2656Y-2.349R.05

G1X.88

G3X.875Y-2.354R.005

G1Y-5.3753

G3X.88Y-5.3803R.005

G1X7.6513

G3X7.6563Y-5.3753R.005

G1Y-2.354

G3X7.6513Y-2.349R.005

G1X4.2656

X4.2356

G3X4.1856Y-2.399R.05

G1G40Y-2.424

G0Z.25

G91G28Z0.

G0G90G55X-4.0

M25(ROTATE BOX TO 270 DEG.)

[john316]

.

 

Anymore Ideas? This doesn't make sense!

 

When you say the second cycle start do you mean the box after the M25 rotation?

 

.

[Roger]

No, I meant that I ran the program, measured the features, (retangular cutout in top, two holes in side) I needed to enlarge both to bring into print size. I put in the wear offset of -.005 pushed cycle start again. The top retangular cutoff was running about a 1/4" off in the Y axis only, and only on the top cutout. It shifted -Y direction.

[john316]

.

 

If that problem doesn't repeat itself you'll probably never know what caused it. You'll have to chock it up to one of those "Just don't know" situations.

 

.

[Roger]

That's what I thought???

[NOTW Programmer]

Do you have to G28 the machine in order for it to read the offset correctly, on our Fadals if we try to run the program again wihtout going home first it will execute the WOFS move from where ever it is currently at and this causes an OT. I guess it tries to move the amount set on the offset page without cancelling the active offset.

[Roger]

No G28 required. If you look at my 1st post, (I've ran this program several times now. And after the 1st cycle every thing ran as programed), I think it's one of "those" problems that will never go answered.

 

I think somehow the machine lost position for a second????

[GIZMO 21]

I think somehow the machine lost position for a second????

thats a scarry thought.