Open loop stepper - 7i96 - following error

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15 Mar 2020 21:23 #160344 by Muz94
Hi, i'm in the process of converting my parport configuration to work with my new Mesa 7i96.
I'm stuck with the following problem: as soon as i try to move an axis the control turns the machine off and returns a following error (this happens with every axis).
There is probably some stupid mistake somewhere but i can't find it.
I would consider my pc latency good (i bought a brand new j4105 motherboard, and with some fiddling i got it to stay below 40'000ns jitter with a dozen of glxgears, an hd video playing on youtube, 3 firefox windows with multiple tabs open, gimp etc...).
I checked my stpgen_maxacc and ferror, but they look fine to me.

Thank you for your help

File Attachment:

File Name: my-mill.hal
File Size:9 KB

File Attachment:

File Name: my-mill_20...3-15.ini
File Size:7 KB
Attachments:

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15 Mar 2020 22:13 #160351 by PCW
Your hal file is setup for running the stepgens in position mode but the stepgen driver is set for velocity mode:

setp hm2_[HOSTMOT2](BOARD).0.stepgen.00.control-type 1

changing this to

setp hm2_[HOSTMOT2](BOARD).0.stepgen.00.control-type 0

Should fix your problem
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15 Mar 2020 22:30 #160354 by Muz94
This fixed it!
I guess I should look better into what I take from sample configurations!
Thank you, I'll let a program run overnight to see if I have any other issues (for now I just have the board connected to the PC in my room).

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27 Mar 2021 19:57 #203831 by Muz94
Hi, i'm reviving this thread because i have another issue.
The machine is working well with the 7i96, and i decided to upgrade the stepper motors with step/dir driven bldc servos.
I bought one, i installed it and from the first test it looks very promising. At that point i decided to try to push it as it should be able to reach 3000RPM without any issues (that would translate in a whopping 30m/min rapid speed!), but i can't seem to push it further that what i did with stepper motors.
The problem is that i run into a "following error" as soon as i try to go beond 7000mm/min on that axis. I also tryed to push to the limit the X axis which is still driven by a stepper motor, but that also generated the same error (at a higher speed, as the X axis is driven with a belt with a different ratio).
What could be the limit in this case? 7000mm/m with a scale value of 401 isn't really even close to reaching the 10MHz limit of the mesa board ((7000/60)*401)= 46'783 pulses/sec). Am i reaching some kind of limit with the servo / base period of linuxcnc? Or is there something else wrong with my configuration?

File Attachment:

File Name: my-mill_20...3-27.hal
File Size:9 KB

File Attachment:

File Name: my-mill_20...3-27.ini
File Size:7 KB
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27 Mar 2021 21:28 #203834 by tommylight
Errors in the ini settings, only Z axis seems to be set correctly.
[JOINT_0]
MAX_VELOCITY = 200.0
MAX_ACCELERATION = 1000.0
STEPGEN_MAXACCEL = 1250.0
STEPGEN_MAXVEL = 190.0 <<<<wrong value, should be more than max_velocity above.

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27 Mar 2021 21:33 #203839 by Muz94
*facepalm*
I wasted all afternoon over forgetting to change those lines. Tomorrow i'll change them too and see if i can finally obtain the speed i wanted.
Thank you, i'll let you know how it goes
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27 Mar 2021 22:31 - 27 Mar 2021 22:34 #203853 by Muz94
While i'm here i ask another advice.
The new servo runs on 36V power, so i had to buy another PSU. At the moment i have 1 12v PSU for the extruder, inductive sensors and other stuff, 1 24v one for the stepper motors and 1 36v for the servos.
I bought my steppers from an insertion which described them as "24V 3A stepper motors". The code on the motors is: 23HS8430.
Looking around online i can't find a voltage rating for them, and i see a lot of topics where people choose the psus for their motors based on torque requirement without speaking of a "voltage rating".
The question is: do you think that i could get reed of the 24v psu and run the steppers on 36v too? The drivers are rated for 42V.
I'm asking this because i'm thinking about keeping the steppers on the Z axis which is only responsible of layer changes (and the stiffness of the steppers is useful to prevent the z axis from moving when the power is removed).
Last edit: 27 Mar 2021 22:34 by Muz94.

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27 Mar 2021 22:47 #203855 by tommylight

Muz94 wrote: The question is: do you think that i could get reed of the 24v psu and run the steppers on 36v too? The drivers are rated for 42V.

Normally yes, but since those are cheap drives with Toshiba TBXXn109 chips i would not push them over 27 or 28V.

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27 Mar 2021 22:48 #203856 by PCW
Step motors are current operated devices, Their maximum speed is determined
by the operating voltage. Usually the limit of operating voltage is the drives,
not the motors so check the maximum suggested voltage of you drives and make
sure its higher than 36V.
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27 Mar 2021 23:27 - 27 Mar 2021 23:29 #203859 by Muz94

tommylight wrote:

Muz94 wrote: The question is: do you think that i could get reed of the 24v psu and run the steppers on 36v too? The drivers are rated for 42V.

Normally yes, but since those are cheap drives with Toshiba TBXXn109 chips i would not push them over 27 or 28V.


I'm using TB6600 drives (or some chinese copy of them). Do you think they might not survive?

PCW wrote: Step motors are current operated devices, Their maximum speed is determined
by the operating voltage. Usually the limit of operating voltage is the drives,
not the motors so check the maximum suggested voltage of you drives and make
sure its higher than 36V.

On paper they should handle 42V, but i guess i might get a bit too close to the limit.
Last edit: 27 Mar 2021 23:29 by Muz94.

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