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[4th axis] How do you set-up your rotary axis?

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16 Jan 2024 10:13 - 16 Jan 2024 10:50 #290853 by Mecanix
[4th axis] How do you set-up your rotary axis? was created by Mecanix
Hey guys. Having difficulties getting consistency between operations. Some works great (indexable drilling for instance), others are instant multi-thousand dollar crashes and what not (simultaneous for instance). Not sure where to begin with this. Let's start with; is Linuxcnc even capable of more-than-three-axis in a relatively consistent and safe manner?

If so, how do you set-up your kin in CAM and Linuxcnc?

0 ~ 360deg?
-360 ~ 360?
-36000000 ~ 36000000?
Modulo mode capable?
WRAPPED_ROTARY - how do you set-up for that one (whatever it does and mean)?

Am I correct assuming Lcnc is set for "unlimited" only? As in only works with outta this world's >360degree angles (aka A32334456degree). Asking because my version unwind the whole 358deg if programmed N1 A359 ~ N2 A1. Really is only 2degree of motion here. Magnitude, sign dir? what's the voodoo again?
Last edit: 16 Jan 2024 10:50 by Mecanix.

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16 Jan 2024 12:19 - 16 Jan 2024 12:19 #290860 by Aciera
Replied by Aciera on topic [4th axis] How do you set-up your rotary axis?
You have probably already found this, regarding WRAPPED_ROTARY
linuxcnc.org/docs/html/config/ini-config.html
 
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Last edit: 16 Jan 2024 12:19 by Aciera.

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16 Jan 2024 12:24 #290861 by Aciera
Replied by Aciera on topic [4th axis] How do you set-up your rotary axis?
Generally I would suggest to have a look at a sim config with a rotary and check things out that way. For example:

'configs/sim/axis/vismach/5axis/table-dual-rotary'

This config has a dual-rotary (AB) table but you can certainly also use it with only the A.
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16 Jan 2024 12:26 #290862 by Aciera
Replied by Aciera on topic [4th axis] How do you set-up your rotary axis?
Also note that the current motion planner will fall back to one line look ahead for any line of gcode that contains more than XYZ. This may cause slow or jerky motion with gcode that contains a lot of short segments.

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16 Jan 2024 13:39 #290869 by Hakan
Replied by Hakan on topic [4th axis] How do you set-up your rotary axis?
Limitless rotation (more or less)
[AXIS_A]
MAX_VELOCITY = 50
MAX_ACCELERATION = 1200
MIN_LIMIT = -9999999
MAX_LIMIT = 9999999
[JOINT_3]
TYPE = ANGULAR
Reset of position at the end of every g-code program
G10 L20 P#5220 A[[[#5423+180] MOD 360] -180]
And a post-processor that generates inverse time feed parameters.

If you just want to position the axis, you may think that A1 is only two degrees from A359. But if you are cutting, together with possible movements in other axes, they are definitely 358 degrees apart. If that's what the g-code says.


 
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16 Jan 2024 14:25 #290872 by Aciera
Replied by Aciera on topic [4th axis] How do you set-up your rotary axis?
For truly unlimited rotation you can also use:

MIN_LIMIT = -1e99
MAX_LIMIT = 1e99

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16 Jan 2024 20:21 #290903 by Mecanix
Replied by Mecanix on topic [4th axis] How do you set-up your rotary axis? 

Reset of position at the end of every g-code program
[code]G10 L20 P#5220 A[[[#5423+180] MOD 360] -180]
[/code]
 

Ah, ok, I see. I admit that is a clever hack to that eternal and weird unwinding issue. With that 'unlimited' suspicion I had I hacked up something similar in post/tcl yesterday (had too) but that G10 ending you've thrown here is for The WIN! and what fix it at the controller end. Thank You So So Much. And pardon my lack of lcnc voodoo skillset, I'm used to old school modulo and DPM hidden inside those industrial ctrl (sinumerik -360 ~ 360) in my case.

Logic for cam postp, in case it helps anyone:
    #------------------------------------------------------
    proc MOM_end_of_program_LIB_ENTRY {position} {
    #------------------------------------------------------
        switch -- $position {
            "start"
            {
                if { [ info exists ::last4thpos ] } {
                    if [EQ_is_equal $::last4thpos 0] {
                        ### do nothing
                        set mom_rot_ang_4th 0
                    } elseif { ([expr $::last4thpos <= 180]) } {
                        set mom_rot_ang_4th [ expr $::last4thpos - fmod($::last4thpos, 360) ]
                    } elseif { ([expr $::last4thpos > 180]) } {
                        set mom_rot_ang_4th [ expr $::last4thpos + fmod(360, $::last4thpos) ]
                    }
                } else {
                    ### do nothing
                    set mom_rot_ang_4th 0
                }
                ### Output rotary return using recalculted modulo angle
                MOM_output_literal "G0 A$mom_rot_ang_4th"
                
                ###Ref: https://forum.linuxcnc.org/38-general-linuxcnc-questions/51373-4th-axis-how-do-you-set-up-your-rotary-axis#290869
                MOM_output_literal "G10 L20 P#5220 A\[\[\[#5423+180\] MOD 360\] -180\]"
            }
        }
    }
    #------------------------------------------------------

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16 Jan 2024 20:28 #290904 by Mecanix
Replied by Mecanix on topic [4th axis] How do you set-up your rotary axis?

Generally I would suggest to have a look at a sim config with a rotary and check things out that way. For example:
'configs/sim/axis/vismach/5axis/table-dual-rotary'

Ok, I will. Baby steps into this for now, that's next-level stuff... I'm barely able to set-up rotary motion for now. Once I get this sorted I'll get into this "advanced" voodoo and report back. 

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