[kiwichris]

Hi folks...

I've got a machine (quickCNC K6100 + CNC4PC C11 BOB + Linuxcnc 2.5) that is running fine, but I recently had a motherboard die, and had a some problems with one Asus board that had massive jitter despite being well-spec'd and then had problems finding a decent board with parallel port on it...

So, I was wondering what the options are for non-parallel port step gen / output to either feed into my existing BOB, or maybe replace it altogether?

It'd be nice to be able to up the step rate substantially and increase microstepping on the controllers as I have a mid-band resonance issue at the moment with 8x microstepping, although the new M/B should be able to do better than the old one and I've not had much time to try it out as I had two weeks down time with the motherboard failure and subsequent testing / hunting for a board.

Anyway.. War stories/ successes, and general emotional outbursts all welcome. :-)

Cheers, Chris H.

[kiwichris]

Just replying to myself :-)

The other question is, should I just buy high spec motherboards and stuff a PCI parallel port in I suppose, I imagine they will be available for some time to come...

[daniellyall]

get a ESS it will future prof your machine bro

[kiwichris]

Ay, saw those on the cnc4pc site, but a bit shy of converting to mach3 as I have 200+ gcode files for products I really don't want to have to revisit

Not averse to suing mach3 itself given it's good reputation, just the pain of changing sounds nasty. ;-)

[cyclestart]

Excuse the laziness but here's a link to a recent post
http://www.cnczone.com/forums/bencht...ml#post1563746

Mesa has linuxcnc packagesthe developer describes as 'plug-and-play'. He's very active on the linuxcnc forums,.

[alan_3301]

I am in the process of setting up a mesa 5i25 + 7i77 on my lathe, I am using analog, but they have step/direction products to, you would use a 7i76
7I76-5I25 PLUG-N-GO KIT
that is a link to the store page, you can search for 5i25 or 7i76 for manuals and more info.

Is isn't exactly obvious how to set up and use, because of so many possible configurations, but there is plenty of reading material and help on the linuxcnc forum.

Have you looked for a old computer with low latency? How high of a step rate would you like?

[Tkamsker]

I use linuxcnc 2.6 and General mechatronics Card Works verry well too ,..


Gesendet von iPad mit Tapatalk

[samco]

the mesa 5i25 by itself would 'act' like 2 printer ports... You could plug your bob right into it. (but it does hardware stepgen, pwm, encoder counting...) and it is $89...

I have been using mesa hardware for quite a while - inexpensive and industrial grade..

sam

[samco]

To add.. You still need 'decent' latency - it just isn't as critical. approx 50 to 75us jitter is acceptable for servo loop only applications (using hardware solutions). (vs wanting <20us for software stepgen)

sam

[kiwichris]

Hi folks..

Thanks for the replies, lots of good info to follow up on...

Alan: To answer your question, I'm currently running 320 steps/mm Top speed of only 3.3m/minute (55mm/s) = 17.6khz. Acceleration set to 350mm/s/s. (5mm screw, 8x microstepping)

The previous motherboard was having stall issues at lower that speed, so I've gained a bit... But it's still not as fast as the machine was with 10x microstepping on the original DSP controller. I retrofitted it as the DSP died and I wanted more flexibility. With the DSP controller it was running 5m/min with 10x microstepping = 33.33khz and I can't recall the acceleration setting off the top of my head. Still not all that fast, but I've always wound up focusing on getting the machine productive and reliable rather than tuning for performance as we have a steady flow of work for it, but don't need straight line speed.

With the motherboard just fitted it might well work at 33khz, it's got a _lot_ lower jitter than the previous one The previous one was. I might give that a go today, but definitely looking to a hardware stepgen solution long term as precision/timing of the pulses and higher microstepping through the mid-band is what gets it up to speed..

Cheers, Chris H.

[kiwichris]

Minor update, had a bit of a play...

Now running 10x microstepping, 4.92m/m (about 200ipm for those so inclined) and 375mm/s^2 acceleration. 32 and a bit khz, and no stalls or obvious mis-steps cutting air on one of my jobs that was causing issues with the old M/B and lead me to reduce settings. at 400mm/s^2 acceleration it stalled out on the first 3axis diagonal rapid.

What is interesting..

Running at at constant 1m/m (39ipm) with one axis I can hear tiny 'glitches' from the motors, like a step is mis-timed slightly. I don't think it's mechanical but I might drop the love-joy joint off an axis and check that out. Very odd.

FYI, running the jitter test I get a max jitter of 2,980ns opening/closing apps and messing about ont he machine. I set the figure in stepconf to 5000, lots of overhead.

Also noted, and possibly an issue with this M/B only. When i switched to this M/B I had to increase the step pulse width to 7500ns was set to 4000 with the old M/B and it wouldn't step at all from the new one... Weak Parallel port drivers one assumes.

Cheers, Chris H.