6 axis DMM servo setup
07 Apr 2016 00:09 #72883
by andypugh
No, it is talking about velocity resolution. That's unrelated to spatial resolution because the PID component can send a different value every 1mS.
So, if it wants the motor to turn at 500.25 rpm it can send 500, 501, 500, 500. in a 4mS period.
Replied by andypugh on topic 6 axis DMM servo setup
So if I had a direct drive setup on a 5tpi ball screw allowing me to go up to 600 ipm then my maximum resolution would be 0.2"?
No, it is talking about velocity resolution. That's unrelated to spatial resolution because the PID component can send a different value every 1mS.
So, if it wants the motor to turn at 500.25 rpm it can send 500, 501, 500, 500. in a 4mS period.
The following user(s) said Thank You: 0jw
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07 Apr 2016 01:46 #72890
by 0jw
Replied by 0jw on topic 6 axis DMM servo setup
Ok, that makes a lot of sense now. Thank you for explaining it. Iv read about position mode being used for point to point applications like pick and place where its not as critical to control speed unlike machining. It sounds like velocity mode could still do everything position mode can.
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06 Oct 2018 22:00 #118504
by 0jw
Replied by 0jw on topic 6 axis DMM servo setup
Andy, you mentioned that it was possible to run 2 7i77 off of a single 5i25? I'm not sure how this would be done other than using a custom Y parallel port cable. I'm confused as to how it won't have conflict with the encoder feedback if two Motors are on the same axis? I'm still unsure of the size of Motors as I don't know the total weight of the machine I've been working on. I had initially planned to use two Motors on the Z lifting the XY gantry and two on the Y and one motor on x and two Motors on the rotational C axis along with one other motor which I met try to use some sort of spindle pwm output for. If I can use one motor on the z-axis that would definitely free up some pins. Although there's a lot more mechanics involved when lifting an entire gantry.
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06 Oct 2018 22:07 #118505
by 0jw
Replied by 0jw on topic 6 axis DMM servo setup
It might actually be an advantage to use stepper Motors on the z-axis since I could take advantage of dynamic braking. Is there any conflict between using 5i25&7i77 along with another 5i25&7i76? I wasn't sure if you can set specific axis to be analog or step/Dir in linuxcnc and haven't found any information on it.
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06 Oct 2018 22:27 #118507
by cmorley
Replied by cmorley on topic 6 axis DMM servo setup
The 5i25 can support 2 daughter boards, but you need to buy a cable to convert from the DIN connector to a parallel port connector for the second one.
So with one 5i25,you could have two 7i77s or one 7i77 and one 7i76 or all the other combinations.
And yes you can have two 5i25's if you wanted.
linuxcnc can have each axis use different interfaces (eg servo or step)
Chris M
So with one 5i25,you could have two 7i77s or one 7i77 and one 7i76 or all the other combinations.
And yes you can have two 5i25's if you wanted.
linuxcnc can have each axis use different interfaces (eg servo or step)
Chris M
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06 Oct 2018 23:21 #118508
by Todd Zuercher
Replied by Todd Zuercher on topic 6 axis DMM servo setup
Unless you need the extra io a 7i78 might be a better choice than a 7i76 for adding step/dir to a 7i77 5i25 combo.
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