Brother TC-225 / TC-229 adventure!

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02 Aug 2017 16:11 #96921 by ihavenofish
it was $8 in the end as i went to digikey. i prefer them and mouser because the parts arrive in 24-48 hours, as opposed to weeks usually from ebay/amazon etc.

so all good i think.

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03 Aug 2017 16:38 #96977 by ihavenofish
transistors delivered, have to wait til tonight to try em :/

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05 Aug 2017 03:16 #97018 by ihavenofish
transistors installed into cable and.... click-clock, works. :) drives are powered by the machine on button in linuxcnc.

on to the drives. it turns out that the wiring drawing for the drives was....

correct! :) x axis running. I did some tuning according to a guide I found on this forum, and its pretty decent actually. I set it to 787 ipm max speed (original speed) and 0.5G acceleration and it tracks kinda ok. I have some questions to see if I can make it better.

first, I am assuming the "1m" scope setting means 0.001 units, which is 0.001" on this machine.

if that's correct, then at all speeds my axis tracks within about 1-1.2 divisions. most of the following error is of course during acceleration. travel is very smooth at most speeds, its a little bumpy "sounding" at the lower end of things (1-2ipm), but following error isn't very big. at constant speed, it tracks very close to 0.

my pid settings turns out to be

P = 125
FF1 = 0.675
FF2 = 0.001
dead band = 0.00001

everything else is 0.

my encoders are 4096 count (1024 line), 5 pitch screws, 4000rpm.

so what would the suggestion be to tighten this up? or is it pretty good as it is?

I also should not, I think 0.5G might be higher than it was stock, OR, linuxcnc's lack of jerk control is making it feel way more aggressive. at low speeds you get a bump start to each move as its basically instant acceleration, whereas the original control seems much smoother.

thanks for all the help so far! :)

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05 Aug 2017 12:53 #97026 by andypugh
You should be able to pull the steady-state error down with a bit of I gain. Your results sound rather good for a P-only control.

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05 Aug 2017 12:58 - 05 Aug 2017 12:59 #97027 by ihavenofish
whats a number to start at for I?

I was a bit surprised how well is came into shape myself, ive tried to tune a few servos before (and easy servo-steppers) and its always been way harder for me. I suspect the drive itself internally is very well tuned making things a bit easier. I mean, I had the following error set at .010" and the default tuning settings let me get up over 100ipm.

:)
Last edit: 05 Aug 2017 12:59 by ihavenofish.

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05 Aug 2017 15:10 #97039 by ihavenofish
soooo, whats the status on jerk control (s curve) anyway? is that coming along, or is it years away?

I reaaaaaaaaaaaaaaaaaaally want it :P

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05 Aug 2017 15:38 #97041 by andypugh

whats a number to start at for I?


I would probably try 0.000001, then 0.00001 and so on.

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05 Aug 2017 16:00 #97042 by ihavenofish
ah, cool.

ok, one last thing I'm about to tackle after I get the y and z and spindle turning...

homing. wiring the actual switches, then making Linux use them as an actual home is easy, but that's not what these are meant to do. they are meant to be home "area" switches, and then the encoder index is used as the actual home position.

how do I go about setting that up?

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05 Aug 2017 16:09 #97043 by andypugh
That's super easy;
HOME_USE_INDEX=1

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05 Aug 2017 22:09 #97047 by ihavenofish
Limits working woot. There's actually a check box for that. Ha.

So next thing.... spindle.
It spins... but it's not accelerating or decelerating fast. I didn't see a setting.

More than that though... where do I start with orientation?

Thanks

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