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Migrating to another PC

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16 Mar 2024 08:07 #296029 by cncjerry
Hi,  
I'm a long time user going back to EMC.  I had a slower machine that is now failing running older linuxCNC 2.7(? grub lists it as debian 3.4-9).  It worked well with my servo system with Gecko drivers. This is on an R45 mill with large servos.  I have 250cpr encoders, 1000cpr in quadrature.  Coupled with the lead screw and timing belts, the system ran O.K. with jitter about 65us.  It was limited by me to 60ipm.  I would occasionally get a halt, usually lifting the Z axis that weighs 240lbs and stopping suddenly.  I remember it ran smoothly up to maybe 70ipm but I would get halts after that. I rarely ran it in G0 speed, usually my G01 rapids were no higher than 50ipm. When I had a faster 3.2Ghz machine on the mill, I easily hit 130ipm and the acceleration was tuned to hit max speed in 90 degrees of the drive timing gear.  But that faster machine died, so I put the slower one on because even with latency of 65us, it had much better latency than others I tried, most well over 100us. 

I would like to get my DL380 G7 working but its latency is up around 110us.  I have an old AMD64 machine that has less than 5us latency so I am going to use that for now. I tried turning everything off on the DL380, latency dropped from maybe 120us to 110us.  It needs a graphics card I think but I can't find an inexpensive card for PCIE 1x, 2x or 4x max.  the other issue is the parallel port on the DL380.  So the AMD64 has 5us latency, a graphics card and the parallel port card works.

So if you are still following along,  I would like to modify my config files taking a machine that was tuned at 65us latency running 60ipm to one with latency of 5us running 130ipm or even faster.  I can easily change the speed in the config files but what else should be changed?  Is there a doc that describes what stepconfig does so I can apply the changes manually to my old config files?  Or should I use stepconfig, generate new files, and then copy in my specific changes?  I can't remember all the timings and pulse counts per revolution, lead screw pitch and timing gear reductions. I know they are in the hal and machine files.

Anyway, thanks for the help on this one and to the others that helped on the thread I started with general questions.  Last I was here, there wasn't a forum, we used a chat for support.

Thanks again,

Jerry

 

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16 Mar 2024 08:46 #296032 by cornholio
Replied by cornholio on topic Migrating to another PC
If you're running from the same HDD & same version of Linuxcnc, nothing needs to be done.

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16 Mar 2024 10:57 #296047 by andypugh
Replied by andypugh on topic Migrating to another PC
I would maybe try a fresh install of LinuxCNC 2.9 and just copy the config files over.
LinuxCNC should auto-convert the config and then you can further update to change the speed limits.

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16 Mar 2024 16:59 #296074 by cncjerry
Replied by cncjerry on topic Migrating to another PC
Aren't there timing parameters in those files based on the latency?

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16 Mar 2024 17:25 #296075 by PCW
Replied by PCW on topic Migrating to another PC
Normally Just the base thread period

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16 Mar 2024 17:30 #296076 by tommylight
Replied by tommylight on topic Migrating to another PC
No, not really.
Latency is the limiting factor, you can run a machine with a very bad latency as long as it is consistent with no excursions over the set limit, and as long as the step rate is enough to run the machine at the needed speed.
I have some small machines that never do over 3m/m, run from a bad laptop for years with base period set at 300000 and x4 microstepping with motors driving a belt at 40mm/rev.
The simple math is, set base period to 50000, save, test, if you get latency warnings set it to 100000, save, test again, raise again till you get no warnings.
After that, and only after that, run the machine to see if it can reach the desired speed, if not - lower the microstepping in half, set the scale in the ini file to half, test again.

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16 Mar 2024 17:31 #296077 by cornholio
Replied by cornholio on topic Migrating to another PC
Only the base thread, which you either work out via running a latency test, or start with your original value and reduce until you get a following error.
Servo thread doesn’t need to be changed.
The docs give an explanation of how it all gels together.

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16 Mar 2024 20:30 #296095 by cncjerry
Replied by cncjerry on topic Migrating to another PC
this is a servo system with 1200oz/in drives at least on X,Y,Z and a 1200oz/in stepper on the A. so I guess microstepping only applies to the A axis and I'll take that into consideration. the base period was 49000 with the old slow machine and this old faster machine is around 35000 so I'll start there. By the way, you can get 128gb internal SSDs on amazon now for like $14. So I bought a few and I'll config them for the older and newer linuxcnc.

Thanks for all the help.

Jerry
The following user(s) said Thank You: tommylight

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