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  • ewlsey
05 Apr 2026 15:47
Replied by ewlsey on topic LinuxCNC S-Curve Accelerations

@ruediger123
For your exact parameters: 1ms cycle, 50 m/s³ jerk, 5 m/s² acceleration, P0.01 on a 45° corner, the only cornering speed that mathematically fits within the jerk limit on a 1ms grid is zero. 
I don't think it's actually zero, but it's pretty close. 
Centripetal acceleration is v^2/r and centripetal jerk is v^3/r^2.

My back of the envelope math says the maximum velocity at a 45 degree junction with .01mm deviation would be .0056 m/s or .336 m/min to keep centripetal acceleration at 5 m/s^2. That would produce a centripetal jerk of 4568 m/s^3, which is an order of magnitude over the limit. 

To keep the jerk within the limit, the maximum velocity at the junction would be .001243 m/s or .0745 m/min. At that velocity it would take 8ish servo cycles to traverse the radius. 

But, for all intents and purposes, it's basically a full stop. 

Wouldn't it be pretty simple to find the maximum junction velocity to keep both jerk and acceleration within the limits of each axis? We have everything we need to make that calculation. Interestingly, since corner tolerance, max accel, and max jerk are constants, this velocity limit is only dependent on the angle. That would make it pretty easy to use a look up table generated by the tolerance setting. 

onehossshay.wordpress.com/2011/09/24/imp...cornering_algorithm/
 
  • PCW
05 Apr 2026 14:53
Replied by PCW on topic Spindle encoder configuration (with G76 threading command and Mesa 7i96s)
For threading, you need a 1PPR signal (index) from the spindle.
  • ziggi
05 Apr 2026 13:54
uspace Dateien updaten - ich brings nicht hin... was created by ziggi
Servus,
Ich hab folgendes Problem: ich benötige wohl ein HAL Modul das nicht installiert ist, einen Konverter "conv_u32_s32 ".  Nun sollte ich dazu das uspace Datei Paket installieren, gegeben wurde mir folgender Befehl:
sudo dpkg -i linuxcnc-uspace_2.9.8 deb
sudo apt-get install -f
Damit erhalte ich diese Rückmeldung:
cnc@debian:~$ sudo dpkg -i linuxcnc-uspace_2.9.8.deb
sudo apt-get install -f
[sudo] Passwort für cnc:
dpkg: Fehler: Auf das Archiv »linuxcnc-uspace_2.9.8.deb« kann nicht zugegriffen werden: Datei oder Verzeichnis nicht gefunden
N: Datei »kcjengr.list3« in Verzeichnis »/etc/apt/sources.list.d/« wird ignoriert, da sie eine ungültige Dateinamen-Erweiterung hat.
E: Typ »’deb« in Zeile 1 der Quellliste /etc/apt/sources.list.d/kcjengr.list ist unbekannt.
E: Die Liste der Quellen konnte nicht gelesen werden.
cnc@debian:~$

Das Paket wird also nicht geladen und installiert
In der Datei kcjengr.list3 steht auch tatsächlich der Eintrag ’deb [arch=amd64] repository.qtpyvcp.com/apt stable main’  kann ich ja nicht einfach ändern...

Nun die eigentliche Frage- wie ist der richtige Befehl um das uspace Paket nachinstallieren zu können.
System: Debian 12, Linuxcnc 2.9

Ich bin leider kein Computer Genie... image missing /media/kunena/emoticons/sad.png

Danke
Sigi

 
  • endian
05 Apr 2026 13:15
Replied by endian on topic Ethercat random jitter fix

 
I saw at my own eyes synchronization of 120 seconds with beckhoff SoE AX5125 driver with older firmware ... its not odd behaviour 

beckhoff IPCs have sometime very similar behaviour with their own hardware from my close experiences...

The more i read here about ethercat = the less i like it.
Thank you for pointing out the quirks, not only the good stuff.
 
ethercat is the best from the best ... everything has some + / - ... finally synchronization issues and these childhood illnesses are not fault of the ethercat protocol itselft which is very robust... Its issue of HW at side of master, slave or connection itself ... 

If we use native bckhff driver at native stuff around these issues are suppressed limiting to zero ...

 
  • slowpoke
05 Apr 2026 12:35 - 05 Apr 2026 12:37
Spindle encoder configuration (with G76 threading command and Mesa 7i96s) was created by slowpoke
I have a 600PPR quadrature encoder linked to my spindle with a 3:1 ratio, so 7200 PPR @ mesa spindle encoder input. A & B quadrature signals only, no 1PPR signal, but I don't think I need the 1PPR signal.

In Halshow
 - spindle.0.revs counts up as expected
 - spindle.0.speed-in appears correct
 - spindle.0.index-enable is disabled

in my SM-10.hal file I have: 
net spindle-index-enable      <=>  spindle.0.index-enable

IF I comment out this line, I can then enable spindle.0.index-enable manually in Halshow

Regardless when I try to open my 2 line G76 program I get the following error:
"Chosen spindle(0) not turning in G76"

I'm not sure if this is a HAL configuration issue or perhaps I need to do something in the gcode prior to the G76 command, not sure?

I have attached files for clarity.

Thanks,
Jeff


 
  • 3404gerber
05 Apr 2026 11:56
Replied by 3404gerber on topic Remora for RP2040
Hi eraserhd,

Thank you for your answer. I'd like to hear more about that spinlock var; I'm a noob in coding but willing to learn. :) I quickly checked your repo and saw that you changed tons of things. I didn't go into the details but will get into the code and test it soon.

On my side, found out that it works stable if I don't use the base thread. And as I'm currently trying to work with TMC5160 in full SPI (with the driver internal step generator), I can live with the servo thread only.
  • zu4lu
05 Apr 2026 10:24
Replied by zu4lu on topic probe basic m6 error
Found it, i forgot the python section in the ini file
  • Drustar
05 Apr 2026 09:09
Help with Lichuan drives was created by Drustar
Hello forum,
I have 6 x 1KW Lichuan LC20 drives and have been trying to get them to work with Raspberry Pi 4B 4GB and LinuxCNC for about 9 months.  I realised I don't have the technical knowhow to make this work.  Using this forum, youtube and Grok, I was able to get close, getting the Raspberry Pi to work as a master and I even got all 6 drives to work as slaves, but trying to get them in to OP mode proved impossible.  On one occasion, when I unplugged 5 of the 6 drives, I managed to get it to go into OP mode but have not been able to replicate it since.  And I have never been able to understand how to get them to turn using LinuxCNC, that baffles me a bit so I have never actually seen the motors work ever.
I am open to buying hardware that kinda works out of the box but I have no idea what that is.  
Can anybody on this forum work with me over time to help me to get these things to work with LinuxCNC, or even Mach???  I can't return them, and after spending $2K on them, I can't afford to buy something a little more 'out of the box'.
Any assistance would be greatly appreciated.
Andrew.
 

Attachment not found

  • jarcysgru
05 Apr 2026 09:09
Replied by jarcysgru on topic Chinese Mesa 7I92 from aliexpress NEW
Witam udało mi się uruchomić z płytą SSK-MB2
to link
Ciekawostka chińska alternatywa MESY - Strona 6 - cnc.info.pl - FORUM CNC
  • jefsaro
05 Apr 2026 07:58
Replied by jefsaro on topic new probe
voila cela fonctionne parfaitement ,il fallait enlever le not sur l 'entree 12
  • Aciera
05 Apr 2026 06:49
Replied by Aciera on topic CSS/G96 for other than X-axis?
Nice!
  • zu4lu
05 Apr 2026 05:22
probe basic m6 error was created by zu4lu
Hi, i installed probebasic on debian bookworm, can reference the machine and jog, but get this error when calling m6: (from the logfile)
qtpyvcp.plugins.notifications - ERROR - pycall(remap.change_prolog) failed
Thanks Michael


 
  • NWE
05 Apr 2026 04:15
Replied by NWE on topic RRW Lab SPI with raspberry pi 5
Is it this?  github.com/cakeslob/RRW_LAB
google does not find it but duckduckgo shows it first
  • grandixximo
05 Apr 2026 00:48
Replied by grandixximo on topic LinuxCNC S-Curve Accelerations
@rodw

Agreed that the planner should be true to the physics, but the physics here has two valid outcomes depending on the machine. A small bounded jerk spike on a 1ms grid at a sharp corner is absorbed transparently by any drive with internal interpolation, the part comes out correct, no stop needed. On a drive without internal interpolation, the spike is real and a stop is the right answer. Both are physically correct responses to the same situation on different hardware.

The point is not to hide the problem but to give the integrator the right tool to handle it. A blind stop at every corner where the jerk limit cannot be met on the 1ms grid would significantly hurt cycle time on complex CAM toolpaths for no benefit on machines where the drive handles it anyway.

The proposal on the table is a new modal G64.1 P Q
jerk-aware continuous path mode that behaves like G64 P Q but adds automatic full stop fallback when the jerk-constrained cornering velocity rounds to zero. Off by default to preserve existing behavior, opt-in for integrators who need provably clean command streams or are running drives without internal interpolation. That seems like the right balance between being true to the physics and being useful across the wide range of hardware LinuxCNC runs on.
  • rodw
05 Apr 2026 00:31
Replied by rodw on topic LinuxCNC S-Curve Accelerations
Yes, I was aware of the issues. Blind workflows where you have little control over the inputs is always a problem compared with a closed workflow.
My thought is you should be true to the physics. If a blind stop is required, do it. If the outcome is undesirable, its up to the user and his client to resolve.

Just because a part can be designed in paper or computer, does not mean it is machinable.
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