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Accumill with Fanuc 3M Control Incremental/Absolute Programming Problem

WakelessFoil

WakelessFoil

Aluminum
Joined
Aug 18, 2020
So I have been running some tests on our old Accumill to ensure it is ready for service in our shop. The latest hurtle that faces us relates to the incremental/absolute function. I have the control default parameter set to absolute mode (Fig. 1). From experience with out newer CNC machine, I would expect to see the actual location of each axis when the machine is first turned on. Instead the machine always boots up with all axis at 0.0000 as if the machine is still in incremental mode (Fig. 2). To temporarily combat this, I turn on the machine, perform a reference point return, reboot the machine, and perform another reference point return (to let the machine know it's at 0). At this point I am faced with another problem, after the last reference point return the axis do not read 0.0000 like I would expect, they read a couple ten thousandths off with pretty fair consistency (Fig. 3). Not sure if this is within tolerance for a machine of this age and nature, but I had to mention it.

Any input is greatly appreciated.

-Justin

Fig-1.jpgFig-2.jpgFig-3.jpg
 
Would I enter that through MDI? Or do I have to run a program with G92 in it? Sorry, I am still a relative novice when it comes to CNC.

-Justin
 
I would just punch it into MDI but it doesn't really matter.

G92 will change the machines current displayed location to whatever you enter in that block.

If you send the machine home and enter G92 X 1.0 Y0 Z0 then that becomes the machines current location.

Whenever you enter G92 it assigns the XYZ values you put with it to the where the machine currently is (and updates the display, the machine will not move.

It's an old school way of shifting zero when you did not have work shift G54 and so on
 
Thanks for the explanation. I now understand G92 much better.

I homed the machine and tried running a program that just contained the G92 function.

PROGRAM:
%
O1000
M5 S1000
G92 X0.0 Y0.0 Z0.0
M00
%

When the program ended I checked the POS screen and the values were not set to 0. I will have to tinker with it a little more.

-Justin
 
It has been over 20 years since I touched a 3 series, but it seems to me that if you pressed a key for an axis (X,Y, or Z) then pressed the CAN button it would zero the readout. Only zero'd the readout. Did not set the coordinate system like G92 does. Try it and see if my old brain cells remember this correctly.
 
Last edited:
If its anything like a 3T- go to the POS screen then hit PAGE and you can scroll thru the different position screens- machine, absolute, relative etc. Go to your offsets page and scroll thru them and see if there is an work shift or offset entered. On a 3T if there is a workshift value entered the position will shift to that value after a machine home. Does a 3T use offsets G52 etc? It might be old enough that only uses positon presets- G50 or G92 etc for x and y. A 3T does not have G52 etc.
 
This is what the first lines in my warmup programs look like, even if the machine has absolute encoders. Power up the machine, select program O98, press the green button, and when the machine stops your good to go. No idea why your position isn't zeroing out, unless as Dan said you are on the wrong position screen so do check that out.

O98
G0G17G49G52G90H0
G91G28X0Y0Z0
G92X0Y0Z0

Drop the G52 if using on a Fanuc 3 control. It was the same hardware whether T or M, only the software was different, as far as I ever knew. The first cnc shop I worked in had both so I have some familiarity with them, but all of my experience with this control is from only those two. The 3 didn't have fixture offsets, only height offsets in X and Y planes when desperate, or G10.
 
We have been told by Fanuc that the 3 series does not have G54 work offsets. They have told us to use G92 for this function.
 
I will try playing with this program next time I am at the machine. Could you give a short explanation of the codes in this program? I am still a novice when it comes to G-codes.
 
Dan from Oakland said:
If its anything like a 3T- go to the POS screen then hit PAGE and you can scroll thru the different position screens- machine, absolute, relative etc. Go to your offsets page and scroll thru them and see if there is an work shift or offset entered. On a 3T if there is a workshift value entered the position will shift to that value after a machine home. Does a 3T use offsets G52 etc? It might be old enough that only uses positon presets- G50 or G92 etc for x and y. A 3T does not have G52 etc.
Click to expand...

Tried this and discovered that there is indeed three different pages for the POS. Second page resembles the first but with dots underneath the X, Y, and Z. I suppose this indicates that the values displayed are actual values rather than values relative from machine boot position. I will have to run some more tests to ensure the programs I input are going off the position from the second page.

Now the only question is why is the display not going back to zero when I perform a RPR? As seen in Fig. 3 from my original post, the POS always returns to a couple ten thousandths off. May have to call Fanuc.
 
What about youroffsets? What does your WORK SHIFT offset page show? For now, it should read zero for each axis. If not set all three to zero and rehome the machine.
 
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