Hidden values for Work Offsets (G110,111,112), Haas VF0

[YendorZenitram]

So this is hopefully a very stupid question, but I cannot find the answer in any of the manuals for this machine. I'm an engineer that's had to get into the dirt of CNC programming.

Where can I find data on how the HAAS controller handles various work offsets. I have a set of simple parts for which I use G110-G112 work offsets.

There seems to be a set of hidden offsets in the machine's computer that I cannot find any data on. Here's a simple run-down of my problem:

1. Select G112 Work Offsets. Go into MDI Mode to run 'G112;' to make sure.
2. Position the table over my physical XY Zero.
3. Use 'Set Part Zero' for both X and Y.
4. Note the X and Y numbers in the OFFSETS Screen for G112.
5. Press the 'POSIT' button. OK, Work Coordinates should be (XY)= 0,0. No.
6. Go into MDI, type in 'G112;' and green button to Run.
7 Back into 'POSIT' Screen. OK, now the Work Coordinates read (XY)= 0,0.
8. This is fine so far.
9. Now, move the table somewhere.
10. Type in a bit of code in MDI mode: 'G112 G92 X0 Y0;'
This should set XY0,0 at current location, which it does.
11. Go back into 'POSIT' screen, sure enough I have Work Corrdinates (G112) reading X=0, Y=0.
12. Go into 'OFFSETS' screen, and the X and Y numbers for G112 are *unchanged* !! This seems wrong!
13. Re-position to physical XY zero position, and use the 'Set Part Zero' to set this location as 0,0. Re-run 'G112' from MDI mode.
14. Now I have X=0, Y=0, but the offset numbers in the 'OFFSETS' screen are completely different from the first time, while XY 0,0 is in the same location.

Can anyone tell me what gives? Is there a resource that explains how the Haas controller deals with Work Coordinate Offsets (something "so easy an engineer can use it!"). The manual and the user interface are inexcusably abysmal, and I'm stuck.

Thanks for any info you all can provide!

[pit202]

why do you use G92 ? it shifts the work coordinate system DON`T use it unless you know what you do , if you wish to move the table just type : G112 G90 X2. Y2. , should be correct.

If you want to have correct numbers after pressing "part zero set" you need to recall the zero point ( in MDI G112 ) before make no sens.

Piotr

[mactec54]

YendorZenitram

What would be the reason to use G110 etc, apart from wasting your companys time money, What happened to G54 to G59

G92 as Pit202 has said should not be in there

There is nothing down & dirty about a Engineer learning how to program a cnc machine,
it makes for a better Engineer, & a understanding on what it takes to make the parts that he designs

[Pondo]

Don't ever type in G92 again and you'll be fine.
It does not set anything, it is an offset shift. It shifts ALL offsets and can fock you up royally if you are not very very careful.
If you are just learning, then I strongly suggest not using it or G52 at all.

[YendorZenitram]

Thanks so much for the replies... I don't ever use G92 in a program - I only used it in my example to demonstrate my main problem: That the numbers displayed in the 'OFFSETS' screen are not the "bottom-line"; there seems to be another set of offsets under these that can affect my Work Corrdinate zero location. My example illustrates that I was able to Zero the machine in the same place, but with two different sets of numbers in the "OFFSETS' screen for G112.

The main thrust of my problem is two-fold:
1. This "hidden" offset is not a good thing. Sure I can work around it, but it represents something I have no control over, and prevents me from using the "operator" coordinates for temporary manual jobs between running work on the G112 Work Coordinate set - something I need to do often in prototyping work.
2. There seems to be no way to goto XYZ=0,0,0 unless you're actually running a program. This works fine for X and Y, but in the Z axis, if I do "G112 G00 Z0;" from the MDI screen - that "Z" location is different from the Z that runs in the actual program loaded in memory.

I know these machine are quirky, very quirky, so is there a place where I can get info on the offset stackup for the Haas system? I'm missing something between the Machine Coordinates and the Work Offset Coordinates.

I've been using and designing automated equipment for 20 years, and this one machine is the first one I've ever come across that I can't figure out, even with it's manual in-hand. Thanks for all the help!

[YendorZenitram]

@Mactec54 - I use the higher set of Work Offsets because this machine is used regularly in production, and those guys use the G54-60 spots. I don't want to screw things up, and I have my own vise on the machine, and use the G110, etc. Work Offsets.

I NEVER use G92 in a program, it was only there as an example to show there's some offset between the Machine Coordinates and the Work Offset Coordinates.

[Vern Smith]

G90 G80 G40 G112
G00 X0 Y0

This will take you to the X and Y offsets currently in the Haas offset table for G112. Short of utilizing some type of macro I have never seen these numbers change due to any hidden influences.

G00 (go to) Z0 will usually not get you a good result, often running the tool into the table. If you want to go to the Z0 position it is relative to what tool you have in the spindle. So--

M06 T2
G90 G80 G40 G112
G43 H02
G00 Z0

This sequence will take the tool in T2 to it's Z0 position, which could still be below some hard object directly under the spindle. It is a good idea to always have the rapids ( G00 ) set to 5% for these exercises.

Vern

[YendorZenitram]

Thanks for the info Vern! Will try that when I'm back in the shop...

Pondo - thanks for the info that G92 shifts *everything*. This means that there should be a ste of offsets that represent the amount by which G92 is shifting everything.

Is there a way to clear any G92 offsets completely out?

[Vern Smith]

There are fellows on this forum that have forgotten more about G code than I will ever know but my understanding is all CNC machines power up in either G90 (absolute) or G91 (incremental) mode. So at this point there is no G92 to worry about. I have always put G90 in my "safe" line (read make sure something isn't on that I don't want to be on) so if another coordinate command like G92 would happen to be on I'm cancelling it.

Vern

[YendorZenitram]

Indeed, I'm no G-Code expert, but have implemented a rudimentary G-Code interpreter and motor control (long time ago)...

At any rate, it sounds like what you're saying is that G90 (or G91?) cancels any offsets or shifts defined in a G92... is this correct?

I'm very surprised at how little documentation exists about these machines.

Thanks! For your info!

[YendorZenitram]

I would also like to ask if there's an easy way to set Zero position for Z on any Work Offset (like G112)?

The method that I was shown by out in-house machinist is to position the tool at Z=0, then go into the 'OFFSETS' screen and add the current Z position from the current tool's Z-offset, and enter that value into the Z offset value for the desired Work Offset. This seems very cumbersome.

It seems you should be able to sipmly move to position with a calibrated tool (for which Z-offset is slready set), make sure you've selected your Work Coordinates (G112), and hit 'Work Offset Meas' and you're done.

Is there a way to do this without having to do the math?