circular wrap at 4th axis

[pit202]

what is a circular wrap and how do I make use of that ?

if I change the parameter bit , I see no difference .

add.

I found some information , it seems that it only affects G28 zeroing and not G1 , is that right ?
what if I wish to make more than 200-500 rotations ?

[HuFlungDung]

I had a job that required many rotations of the A axis to get to various A positions quickly within a program. If you can visualize milling a long screw thread, then you can imagine that several full rotations are required to complete the job. If there are multiple passes to be completed, going in one direction only, you can imagine a lot of wasted time as the control unwinds the A position for the next cut.

The setting "quick rotary G28" should be on, but that is not the end of the story, at least on my Haas which has older software on it.


I made good use of G92 to control the A axis behaviour. At the completion of one cutting pass, I made whatever additional movement was required to bring the A axis exactly to the 360 (0 degree) position, with commands of less than 360° length. Then I used:
G92 A0
to rename this position at zero, made a simple rapid linear movement back to the X start of the part, and commanded the next XA movement in typical manner.

As with any use of G92, you must know where the axis is located at the moment the command renames the display, so that you do not lose your A reference point. That is why I say to end a long A movement exactly a full multiple of 360° turns.

At the end of the program, I went in to the offset registers to look at the accumulated G92 value assigned to A. Quick rotary G28 does not cancel this value out, even though the head returns to its zero within one revolution, so you have to do it yourself, with another G92 command of equal but opposite magnitude at the end of your program. If you fail to cancel what is in the G92 A register, you will still experience the phenomenally long wait while the axis unwinds at the beginning of the next run of the program. The Haas keeps track of all G92 commands in a cumulative manner.

Here are the program end lines that I found would work properly in conjunction with the quick rotary G28 parameter being on:

G00 G91 G28 Z0 A0
G92 A(inverse of amount in G92 register found after running program through once)
G00 G90 G53 X-20. Y0.
T1 M06
M30
%

In the course of doing this, I found the control had some quirks: I had programmed individual movements as long as A5400.000 to A-5400.000 and my total cumulative G92 commands got me up as high at G92 A86400 for an offset. The jog handwheel would not jog the A axis any higher at this position, but the control still would run the program ok.

Now if in the course of setting up to run your program, you abort part way through, and have been using G92, then there could be some residual amount in the G92 A register. You can also zero this register out manually before rerunning the program to avoid the unwind thing.

[Geof]

Yes Circle Wrap needs to be turned on for Quick Rotary G28 to send the rotary to the nearest Home position without upwrapping many, many complete revolutions. It does not affect anything else just the G28 homing.

You have to turn on both Circle Wrap and Quick Rotary G28 and I think one is a Parameter and one a Setting.

[crabbass]

Is the cumulative number (say A84000) stored in a parameter? (say #xxxx)
Couldn't you zero this parameter by programming

N1000 #xxxx = 0.
N1010 M30 ?

And if the Haas setting to "pre-read" the program when restarting is on, does it re-count all of the programmed rotations and add them to the counter?
If it isn't stored in a parameter, where do you look to see where it is at?

I have manually programmed some 4th axis work where the A rotation was incremental, The total cycle probably only accumulated to 20 full 360deg rotations. I was using g28 with the quick rotary setting on.(not cylindrical wrapping) and was confused as to why it would still unwind when starting the cycle again on the next part. I do not normally use the G92 command, as I haven't had a relevant need for changing the zero point(or maybe I have). This is a good example of how CAM can rob our brains of basic g-code knowledge.
Thanks for the clarification.

[HuFlungDung]

Originally Posted by crabbass Is the cumulative number (say A84000) stored in a parameter? (say #xxxx) Couldn't you zero this parameter by programming N1000 #xxxx = 0. N1010 M30 ? And if the Haas setting to "pre-read" the program when restarting is on, does it re-count all of the programmed rotations and add them to the counter? If it isn't stored in a parameter, where do you look to see where it is at? I have manually programmed some 4th axis work where the A rotation was incremental, The total cycle probably only accumulated to 20 full 360deg rotations. I was using g28 with the quick rotary setting on.(not cylindrical wrapping) and was confused as to why it would still unwind when starting the cycle again on the next part. I do not normally use the G92 command, as I haven't had a relevant need for changing the zero point(or maybe I have). This is a good example of how CAM can rob our brains of basic g-code knowledge. Thanks for the clarification.

If you go into your work offset pages on the Haas screen (older Haas anyways) you need to page down once or twice because they show the G92 offset register at the bottom of the list. My last few entries in the list I see, ends at G118, then G52, then G92 IIRC. When you've got 4th axis enabled, you'll see the A in one column, otherwise, its not there.

I'm not saying that you cannot also control the same thing with a variable, I just an not familiar with which one it would be.

I have heard from others that the Haas quick rotary G28 doesn't work as they'd like. If you don't actually use any G92 calls in your program, I doubt that you would see any 'accumulation' in the G92 A register. But if they're using a G92 command within the control software (what else could they be using in actual fact) to execute the quick G28, then maybe there is a hidden value in there somewhere that is not properly cancelled and so results in the unwinding at the rerun of the program. I have not experimented with the quick G28 on any program that did not use a G92.