just another plasma build and then some :)

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21 Apr 2020 20:42 - 21 Apr 2020 20:43 #165004 by machinedude
he has all kinds of video's and was looking a little this morning and it looked like he was using a 7i76e with the 7i85 s so if this is the case it should be no problem to add the THC cards to it down the road if this sorts the lag issues out on positioning. Linux cnc is one of the few systems that can do this from what i have seen.

glass scales are out for me but magnetic scales look like a perfect fit for my application. my traverse speeds are not crazy fast so the reader heads should pulse fast enough for my machine easily.

i like my coffee so i got that part covered :) that's the easy part :)
Last edit: 21 Apr 2020 20:43 by machinedude.
The following user(s) said Thank You: tommylight

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22 Apr 2020 00:23 #165025 by machinedude
found his project over here and this is the link to it.it looks like he had the hybrid steppers with encoder feedback already and made a dual loop feedback system? i seen mention of PID so this a research project from the looks of things.

forum.linuxcnc.org/49-basic-configuratio...le-closed-loop-setup

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23 Apr 2020 10:09 #165202 by machinedude
was reading a white paper on closing the loop on steppers and seen the real magic happens in the drive's. this paper made reference to running them as a 2 phase brushless servo ? i might check with gecko to see if something like this can be done with their 320x drives? they are about the same cost as the stepper drives honestly. basically you need a drive that knows what to do with the feedback from the encoder. but if something like that would be something that would work changing the drives out would be money well spent to have a machine that can position to the same resolution as the encoder your using. by using a linear encoder you bypass the the backlash and screw lead variations all together which is what i am after.

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23 Apr 2020 10:47 #165209 by tommylight
I think with G320 that will not help, but it still might improve the accuracy a bit. If i remember correctly those geckos will error out if they miss 128 steps of the encoder, and that can not be adjusted. To much for low resolution encoders, to little for high resolution encoders.
Also check if yours have a divider by 10, Gecko uses that on most of the drives, and i hate it, having the drive do nothing for 10 steps is not good for precision. I know i took that out on mine, for sure, they should be on a small board near the inputs.
Although that is helpful when using parallel port as you can achieve 10 times the speed at the cost of resolution and precision.

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23 Apr 2020 10:57 #165215 by rodw
Make sure you get some feedback from Stefan about the gecko Servos. I don't think they are a good choice.

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23 Apr 2020 11:42 #165230 by machinedude
the 201x drives i have are pre set to 10 micro steps and they have no adjustment in that respect so it takes 2000 pules to get a rev out of the motors. right now i am running off the parallel port but that's just temporary for now so i can sort things out somewhat. once you go to a motion control board i think you get better performance out of the machine as a result.

if they would miss to many steps and alarm out that could be a good thing to a degree in the sense the machine stops so you can fix the problem before it's to late to save a part. lost steps are just a short coming of stepper motors in general.

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23 Apr 2020 11:56 #165238 by machinedude
one other thing that got me thinking pretty hard on the topic was getting that long screw to hit a size on a part 5 foot long. i used a set of 24" digital calipers and worked my way through 2 foot of travel 2 inches at a time and the lead inaccuracies can stack up fast. they actually would rise and fall over an average so looking at a longer section of travel is what it took to get larger parts to come out right. getting things tuned on the long axis was a real pain in the you know what :) that's what sparked the idea of linear encoders to track actual position rather than a rotational drive calculation .

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23 Apr 2020 11:58 #165239 by tommylight
Not microsteps, they just sit quietly for 9 steps and move on the 10'th.
And they do have a fault output that can be used to stop the machine and given an input for each of them you know what axis faulted.
The issue is that that same pin has to be set high for the drive to get out of fault condition, and that is a bit tricky to do as it needs an input and an output wired to the same pin on the drive. An open collector output can be used for that, but i never tested it.
I still have two G320 somewhere collecting dust, so i might try to figure something, if there is interest about it. So far i know two persons using that, just for fault signalling.

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23 Apr 2020 12:25 #165247 by machinedude
i thought i seen something about fault signals in the manual for the 320x? i will have to go back and look at it some more i just skimmed through it real quick. for a servo dive it is not fancy by any means but it would work with everything else i am using with no problems on the DC power supply and amps on the motors i have now. i just don't know if it would work with a bipolar stepper motor or not? it works off of just step and direction signals from what i seen at first glance. this is a mixing of stepper and servo parts and becoming a real frankin mess of sorts :)

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23 Apr 2020 12:32 #165250 by tommylight
320x is a DC servo drive, so it does not do steppers.
It does step/dir as normal stepper drives, though. And have a fault pin that has to be set high ( at 5V ) to enable the drives.

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