Old Haas VF/4 - Setting Grid Offset on a rotary.. anyone know how to calculate

The Son and I had been on this all day. Time to post a bit and see if someone could straighten us out. (and it's my own online record).

...the short of our current status: We went back to using TC Offset #212 values w/ #269 TC offset =1, but we really just wanted to see if we could figure out how Grid offset value (#128) worked on these old VF w/ rotary's attached to the VF itself.

Grid Offset experiment: (#128 A)
Haas 98 VF/4 9.64N OS, -
TRT210 rotary now installed (and level ;-) (a TRT is an HRT210 with a HRT160 bolted to it as B)..

Why he was trying: The Home position on the A rotary: (mechanical home on power up) is in a funky spot. It's upside down and slanted 30 degrees. SETTINGS: ( w/ #212 TC offset = 0, #269 Zero Axis TC=0 and #128 grid offset = 0. )

Attempted: When we enter a grid offset: -4000 input to #128 and restart. (#212 is still 0 on this) . result: We can get it to roll back about 2-3 degrees in the right direction. It's about 140' degrees too short for what he wants.

Hey... maybe we just start increasing #128 values...-6000 issued an error grid offset too small. same for -8000. error. I stuck in -17555 (just for kicks) and turned it off after it did a roll back over 200 degrees from the limit. We cannot seem to figure out a formula for how you get grid offset to move x-degrees. Rotary manual notes that #128 is a Modulus of Parm #47 (say's a manual when using the devoted controller for rotary and it's not connected directly to the Mill). So I tried playing w/ a few modulus values via the formula in the book. To try and get larger modulus values. blah! I'm not calc'ing it w/ the right values if this is even how you do it.

We did play w/ #212 TC offset early in the day. Had it the way he wanted it until he setup a custom Macro M6 = M9000 macro to move everything around for his tool change. We can make that work w/ a little more tweaking. just wanted to learn grid-offsets. Uncle!

As a sidenote tip: It took some digging to find out that any values in #212 for TC offset on A did nothing till #269 TC offset bit was flipped to a 1. We found the tips for going into DEBUG and trying to get the values from the raw screen... but those calc's from online did not work either in #128.


REF note #1
**(Best desc. I could find on Grid Offset calc, but I could NOT get any values to dial in the back-off value on a rotary HRT/TRT unit. (as noted in core text above).
I will explain this as best I can. When the machine is "zeroed", the axes travel to home switches and then back away from the switches to a specified offset. This grid offset becomes the zero point when the machine is in use. This alarm you are getting indicates that the margin is too close to the switch.
You can also look for chips on the trip flag. Chips can sometimes cause the switch to trip too early. You didn't mention any other problems with the machine, such as excessive backlash, but this can also cause a grid margin alarm in extreme cases.
Sometimes, no problems can be found and then axis simply needs a grid offset adjustment.
In Zero Return mode, the distance to go that is displayed on the screen is the amount that the motor rotated away from the switch to the grid offset. The alarm will occur if the distance to go becomes less than .0295 or greater than .2065. The ideal amount is .118.

Here is the procedure for setting the grid offset:

1. Set the grid offset to zero. (Parameter 125,126, 127, 128, or 170, (depending on the axis being set.) Always write down the original value.

Setting #7 (Parameter Lock) must be OFF and Emergency Stop button pressed in before any parameters can be changed.

2. Press Zero Ret, then the axis you are setting (X, Y, Z, A, or B), and then press Zero Singl Axis.

3. Calculate grid offset using the following formula, and write the result in Parameter 125 (X-axis),126 (Y-axis), 127 (Z-axis), 128 (A-axis), or 170 (B-axis).

(Distance to Go - .118) x Ratio = Grid Offset.

The Ratio (steps/unit) for the X, Y, Z, A, and B axes are the values in Parameters 5, 19, 33, 47, and 155, respectively.

When finshed, cycle the power on the machine and test it.

I posted in this forum to a thread for someone trying to shift their 5th axis, but I can’t find it. If I don’t find it, I’ll repost the way I do it tomorrow after I get to the shop. It’s for an 05

Ok found it.
Put your A where you want it.
Unlock parameters setting 7
Enter debug mode.


Take the value in the "Target" column for the A axis and write it down.
Now page down on the "Position" page until you find the page "A Param A”.
Under "Tool Change Offset" (Parameter 212) there is a value.
Take "Tool Change Offset" value minus "Target" value and enter that new value into parameter 212.
Zero return your A and double check it.

No need to hit e-stop.

This works on my 05. If it works on yours, you can do the same thing with you B by using the corresponding B axis values.

Hope this helps.

...and here is the text from the Rotary manual for grid offset and the modulus portion.

Parameter 45 (91): Grid Offset (0 to 99999)
The distance between the home switch and the final stopped motor position after homing, is added by this gridoffset amount. It is modulus of parameter 28, which means if Parameter 45=32769 and Parameter 28=32768,
then it is interpreted as 1.

So ... I'll get this understood someday.

BD.... THanks!!! thats exactly what we needed to now use #212 and get it where he wants it.

Peace!

I put the rotary where I want it to be, go to the work offset I am using curser over to "A" and push the set work offset button.