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Messages - skunkworks

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23ms jitter would be bad...  (Unusable). My guess is that it was actually 23us of jitter.  This would be a average jitter for rtai real-time extensions.


Hi skunkworks,
my apologies to OP if this is off topic.

I have seen that Linux CNC uses RealTime Extensions to achieve realtime performance. I also saw a video where at the end of the
installation of the Linux distro (with the RTE's) to test the realtime performance. The video of the system under test reported
'a jitter of 23ms'. This was reported to be normal and adequate for LinuxCNC.

Can you clarify what it was that I saw, I would not have thought that a communication loop which included 23ms jitter would have been
anything like sufficient for a realtime feedback controller?


This is a situation that really requires you to have access to the realtime layer of the control.  (like guts of the ess)

Linuxcnc you can sense -> model -> act a _minimum_ of 1000 times a second.  (1ms) Because the realtime bits are actually in the computer - you can do this.

Or re-invent the wheel with an arduino or such.


Mach4 General Discussion / Re: Glad |I asked first
« on: February 11, 2018, 04:29:21 PM »
I agree - it is always best to remove backlash.  That being said - bc does work decently well. 

this is 2 circles - one with bc off and one with bc on.  can you see the difference? 

Mach4 General Discussion / Re: Real G93 Gcode anyone
« on: February 06, 2018, 02:47:05 PM »
that looks better

Mach4 General Discussion / Re: Real G93 Gcode anyone
« on: February 06, 2018, 10:46:16 AM »
RDR's first gcode looks plausable...  But there seems to be an extra cone and cylinder.

mauri's one looks odd to me - (atleast it doesn't look like the stl...)

well - not quite...

Linuxcnc has had the capability to run Ethercat directly for a while now. 


PC's are certainly suitable for realtime determinism.  (and you can do it cheaply) with the right OS.


EtherCat Master is a realtime system, PCs are unsuitable as is and the solutions to achieve realtime determinism are just to expensive
for me to get into as a hobby project.


sorry..  i failed at reading comprehension..  ;) 

That just looks like a normal breakout board.  Are you using Darwin (printer port driver) with mach4?

CS-Lab / Re: ENC threading module setup for ridgid tapping
« on: May 13, 2016, 10:04:05 AM »
I think I have a bit newer matsuura we are in the process of converting.  I ran into the same problem with the spindle - how to mount an encoder...

Our solution was to mount a gear and use a gear tooth sensors for the quadrature and index.

It is a 69 tooth gear so that is 276 counts.  We are in the middle of the conversion but I was able to rigid tap in air - seemed smooth.


linuxcnc has the kinematics to do this sort of thing. (joint to world and back) It is not for the faint of heart..


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