Hello Guest it is April 15, 2021, 08:46:14 PM

Author Topic: Rotary Axis Help  (Read 10846 times)

0 Members and 1 Guest are viewing this topic.

Offline RICH

*
  • *
  •  7,419 7,419
    • View Profile
Re: Rotary Axis Help
« Reply #10 on: January 09, 2010, 10:19:49 AM »
Whenever you try something new you become a beginner. Shortening a learning curve for someone is my pleasure when i can do it. Mach is so configurable and it's use can go from basic to complex very quickly depending on how much of that configurability you want to implement. And you don't learn it in a short time thus I consider myself a beginner also. Can't realy complain about the manuals since a book could be written on every subject.

The write-up curently has some 100 pages of stuff / notes in it. So a lot of sorting out to do to put similarities into perspective. What it will cover, when you will see it, how much effort will go into it,I can't say.

Till then, keep on posting, as i am sure there is someone that can be of help,
RICH
 

Offline RICH

*
  • *
  •  7,419 7,419
    • View Profile
Re: Rotary Axis Help
« Reply #11 on: January 09, 2010, 12:20:11 PM »
Brett,
My modified work saying is "You don't know how stupid you are until you get into something you haven't done".

So I do a fair amount of research on things that apply to something i would be doing or of interest to me. The learning is fun. Then as a beginner you find all the poop, or question why something seems too difficult when it should be easy.

The rotary stuff just happens to provide a good machining option for the 44 MAG model i am working on.
Sometimes you need to expand the horizon to accomplish a task.So preparation is fun also, but successful
application is even more enjoyable. 

BTW, Richard already has a cnc sickness. One of the symptoms as you know, is the needed feeling of rotary movement.  Corruption through ease of setup is only one treatment and my license to practice is limited. So will refer him to a specialist if the condition doesn't improve.  ;D
 
RICH   

Offline Chaoticone

*
  • *
  •  5,626 5,626
  • Precision Chaos
    • View Profile
Re: Rotary Axis Help
« Reply #12 on: January 09, 2010, 01:07:12 PM »
 ;D

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!

Offline RICH

*
  • *
  •  7,419 7,419
    • View Profile
Re: Rotary Axis Help
« Reply #13 on: January 09, 2010, 01:37:04 PM »
Now on the corruption of the lathe screen that occured.
That G00 A360 Z ( or what ever axis ) 12 is a dumb command, maybe should of recieved an error, but,
it realy screwed up Mach. I just replaced the xml associated with an earlier one from the backups.

When it happened, you could not move the A axis ( even if you went in and out of Mach or used another different
lathe screen ) in fact when i tried to jog / mdi say the x  axis ....no joy. Went out of mach and tried using Mill and all was OK. Tried again a few times with three different xmls / profiles ...no joy...and one time the x axis just took off unexpectantly ...real suprise on that one. It was not until the corrupted XML was replaced that things went back to normal. 

RICH

Offline Chaoticone

*
  • *
  •  5,626 5,626
  • Precision Chaos
    • View Profile
Re: Rotary Axis Help
« Reply #14 on: January 09, 2010, 04:43:01 PM »
Is normal even a word?  ;D

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!

Offline Hood

*
  •  25,838 25,838
  • Carnoustie, Scotland
    • View Profile
Re: Rotary Axis Help
« Reply #15 on: January 09, 2010, 04:57:44 PM »
Is normal even a word?  ;D

Brett

Definitely not if referring to SC residents ;D

Hood
« Last Edit: January 09, 2010, 04:59:30 PM by Hood »

Offline Chaoticone

*
  • *
  •  5,626 5,626
  • Precision Chaos
    • View Profile
Re: Rotary Axis Help
« Reply #16 on: January 09, 2010, 05:07:48 PM »
Thanks Hood. As usual your there to help out. Eliminated a little confusion for me. I thought I had missed something.  ::)

 ;D

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!

Offline RICH

*
  • *
  •  7,419 7,419
    • View Profile
Re: Rotary Axis Help
« Reply #17 on: January 09, 2010, 06:47:13 PM »
Richard,
Back to normal now.   :)
Like Jeff said, "I am assumning  If your 4th axis is your lathe spindle, it will need some feedback from a servo motor with encoder or a stepper motor. This is needed to know where it is positioning in relation with the bed or cutter." So additionial config is required
in addition to what was posted.

Do have any feedback? What kind of motor are you using?
If no feedback, and A is rotary,then the feedrates shown will be useless , some of the rotary settings won't work, and coding and setup may be better done via a linear setup. A single index won't work to well,this is especialy true if the spindle rpm is slow or your indexing. In my case, for what i am doing, turning at just a few rpm ( 10 rpm max and 1-5 will seem normal in the moves), and my setup is linear.

Just a heads up, ;)
RICH
Re: Rotary Axis Help
« Reply #18 on: January 11, 2010, 09:36:54 AM »
Rich,
The 4th axis is the spindle and is driven by a stepper. I found the problem, it was with the post processor. Although the processor I had loaded indicated it was Y-A, it was actually doing an X-A conversion so the A wasnt being coded to move. Once corrected it is now working. I cut some pieces over the weekend and although it still needs some tweeking it cut the parts accurately and didnt break anything, success!  I will definately keep my eye open for your finished instruction on this process.

Richard
Re: Rotary Axis Help
« Reply #19 on: March 28, 2010, 10:00:16 AM »

I'm setting up a 4th Axis and looking to optimise the G0 movements.  Gantry CNC with stepper controller 4th rotary.
I'm not sure if the "Ang Short Rot on G0" will help when G1 commands exceed the 0 to 360 movements.

GCODE example...

% (F_CONTOUR12_T1A.TAP)
% MILL_TURN_PART_TRIAL -----------------------------------------
N5 G17
N10 G21 G40 G49
N15 G53 G50 G90 G94
N20 M48
N25 G54
N30 S6000 M3
N35 G0 Z22.
N40 G0 A0.
N45 (-------------------------)
N50 (F-CONTOUR12-T1A - PROFILE)
N55 (-------------------------)
N60 G0 X18.064 Y55.325 Z22.
N65 G0 A270.
N70 G0 Z19.5
N75 G1 Z14.5 F100
N80 G1 A630. F3985
N85 G0 Z22.
N90 G0 A270.
N95 G0
N100 G0 Z16.5
N105 G1 Z11.5 F100
N110 G1 A630. F3985
N115 G0 Z22.
%--------------------------------
N120 G0 Z22
N125 M5
N130 M9
N135 G40 G49 G80
N140 M30
%

The issue with this example, is that with "Ang Short Rot on G0" ticked... the A630 commands are completely ignored.  It has to be with 0 to 360.
It does this with or without "Rot 360 rolloever" ticked.

The post-processor is kicking out this code, and it's getting difficult to figure out how to optimise it there.  But currently this type of code is causing excessive rotations.   If I did a 10 turn spiral slot with two passes, the rotary is going to unwind 10 turns at the end of the first pass before starting the second.

The only other way I can think of is to implement a function in the gcode using G92.  For example, for a G0 command it would first G92 mod(A current position / 360)*260, then G0 to new location.  This won't provide shortest path though, unless I get more complicated with maintaining a variable for the rotarys position (getting messy). 

What I believe would be needed...
G0 shortest path followed by a DRO update for 0 to 360 position.
G1 commands function without angle wrapping or any modification to DRO position. 
So feed commands function exactly as intended, however G0 rapids via shortest path and resets the DRO to the 0 to 360 range, ready for the next procedure.

Do I have my logic correct, or have I misunderstood how this could be implemented?

Otherwise, would it be possible to somehow setup a gcode command to turn on and off the "Ang Short Rot on G0".  This would enable me to turn it on, G0 to next position by shortest path, G92 to restore the DRO to where it would have been given unwinding, then turn the "Ang Short Rot on G0" function off.  I could easily add this on/off to the G0 rapids in the post-processor and all would be neatly solved :-)


Would appreciate any comments.