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Messages - fristot

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Oups! you are right Ian: Mach3 is fine, and my recorder is wrong.
Reading again my code, I found I forgot to latch my positions counters (the ones that get incremented or decremented on PIN interrupts) before using them. As a result, by the time I output these to the serial port, they were altered by the interrupts.
Now I corrected the code, and everything is fine on both the parallel port and smoothstepper (just one pulse off on rare occasions, which is what one would expect).
I am very sorry about raising this false issue. I was too happy to find a beginning of solution for my still unexplained little wave patterns on the parts printed by the machine..

I will edit my first post, or maybe if a moderator is listening there, it might be better to just remove this all thread ?

well, it seems I cannot edit my first post...

I used the smoothstepper for the first test, and parallel port 25kHz kernel for the second. Both tests on the same Laptop (X31). Mach3 R3.043.066
Interesting to see that Stirling is not seing this. I don't have a logic analyser but I am pretty confident about my test setup, and it makes good sense since the master and slave positions always end to the same value when motors stop.
Maybe there is something special when nearing the 25kHz kernel limits (9000mm/min with 160step per) ?
I will do some more tests.

Hi, thanks !
 I contacted Greg and he will have a look at the issue. In the meantime, I replicated the experiment using Mach3 + parallel port. And it appears that there is also a noticable difference. Attached pic.
Does anybody have a plugin to record the trajectoryBuffer of Mach3 directly ? I'd like to check if the trajectories are also different. I suppose so. But why ?
Thks in advance,

I am working on a very large 3D printer using Mach3 and smoothstepper. The B axis is slaved to X and C axis slaved to Y. Because we see little unexplained waves on printed part surface, I designed a recorder with a microcontroller and interrupts  to calculate the theoretical axes positions from the step/dir outputs of the smoothstepper. I record these positions every 2 milliseconds. So I just use the PC+smoothstepper+recorder, no noise, clean pulses.
During the tests, I expected  the master and slave axes to receive the very same pulses, but to my surprise, there are errors. Attached is a graph of the master axis position (in Pulses) and the Positionning error (in Pulses) compared with its slave axis. The experience can be reproduced with the same behavior; Up to around 20 pulses difference !  This may sound low, but we have low step per unit (160 per mm). Our parts surface is textured with low amplitude sinewaves (around 0.2mm peak-peak, not due to mecanichal noise, as these waves have precise and reproducible positions), but still visually unpleasant..
Did anybody realize there was a master/slave difference, and how could this be improved ?


Brains Development / Re: Brain to trigger home or probe input
« on: October 16, 2014, 06:25:28 AM »
Hi Thomas,
We can align the motors because we have individual outputs to enable each motor separately, so we can home all, then home one by one. This works with a Or function of home switches (we had switches in series and validated the procedure. Now we use optocouplers, and it is just more difficult to "or" their output..)

Brains Development / Re: Brain to trigger home or probe input
« on: October 15, 2014, 09:56:09 AM »
Hi Thomas,
Thks for your input. I must admit the Ascii art is somewhat easier to understand than plain text, especially when describing elec schemes...
I also disable step inputs of some motors when I want to make individual motor homing procedure. But I cannot replicate your signal relaying because my machine goes beyond home switches in some occasion (home is not limit switch here).
In present case, I mostly wanted to avoid extra hardware, since the machine is to be delivered soon and software changes are always preferable then...

Brains Development / Re: Brain to trigger home or probe input
« on: October 15, 2014, 08:21:10 AM »
Hi Scott,
Thks for your reply. I like the Ascii art.

I have implemented the brain as described and it works only for the Home DRO in the diagnostic screen, but it will not stop the motor while homing. Too bad.

I thought brains were much faster than 1/10th of a second, so or'ing the signals in brains seem useless anyway.
In the meantime, I had contact with smoothstepper tech support and they told me that general input and outputs were updated only at 10Hz, while homing input is controlled internally (in the smoothstepper if I understood well) so as to stop motor quickly when homing.
I think I am left with the hardware solution - back to the old 74xx TTL logic series..  hum, glorious times.

Thanks again,

Brains Development / Re: Brain to trigger home or probe input
« on: October 14, 2014, 09:19:13 AM »
I forgot to mention that I am using a smoothstepper. (I did'nt find a solution using parallel port either).

Well triggering inputs might be beyond possibilities, even for brains. Too bad.


Brains Development / Brain to trigger home or probe input
« on: October 13, 2014, 11:51:59 AM »
For a large 3D machine using 4 Z motors in "parallel" (same step/Dir, but each motor can be individually disabled upon accurate homing), I'd like to make a brain to OR all my 4 Z home inputs and create a HomeZ signal that is compatible with the homing procedure (Z ref).
I made a brain which output is actually the homeZ input, and it works in the diagnostic screen (Home motor Z gets activated), but the reference procedure cannot be started as Mach considers that the Home Z input is not defined.
-Same problem using probe input instead.
-I could hardwire my OR function, but this is not easy with the optocouplers I have now.
-I could probably activate an output using the brain, and connect it to a physical input pin, configured for Z home. But I have no more outputs (except on modbus, too slow)
-I fear a vb code reading directly the inputs to stop the homing will be too slow.

There may be a way to activate an internal register using the brain, which could be read as a port input for home Z definition ? I know that writing a parallel port data register does not mean I can read it and get the same value afterwards..
Possibly I could let Mach3 think the homeZ pin is configured when it is not (if I configure it to another port pin, then the brain will not change its state).

Any idea ? I would really want to avoid making a board just to OR my 4 signals... - even using diodes I find it not so cool when there should be a clean soft way.


General Mach Discussion / Re: accuracy issue -solved
« on: May 12, 2009, 11:28:28 AM »

I can't believe it ! It was actually simply a loose coupling between the motor and axis.  I tested it though. It was very hard to resist by hand.
But I think that with the vibrations, it could make some angle shift...  Now it works.

Thanks a lot Jeff !


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