Hybrid steppers or servos?

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28 Sep 2020 12:24 - 28 Sep 2020 14:24 #184156 by RoberCNC
Replied by RoberCNC on topic Hybrid steppers or servos?
After adjusting the parameters in the INI according to the documentation table and performing some more tests, I have observed a very curious detail. The greatest deviation occurs in the initial travel, that is, I adjust the axis to zero, I adjust the dial indicator to zero and on the turn of the first travel is where the deviation falls brutally, in successive it repeats more or less within a range acceptable.

To rule out possibilities and further testing, I have put a 2 second delay between travel and travel in the repeats program but it does the exact same thing.

Does it make any sense? What can it point to?

Thanks, Rober.
Last edit: 28 Sep 2020 14:24 by RoberCNC.

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28 Sep 2020 20:45 #184209 by tommylight
Since i have lost track of this topic, i am assuming you are using stepper motors and drives:
To avoid wasting more time, set the step space and step length to at least twice of what you have now or to at least 5000, set the dir stuff to 20000 and test again.
After that you can also set the microstepping on the drives to 1 and edit the ini scale accordingly, and just in case this fixes things that would mean that the drives have badly implemented microsteping or the motors are of very low quality.
If using closed loop steppers, the timing is the first thing to check.
In both cases, do not use microstepping with 1000 or 4000 or similar values, use the x16 or x256 values.

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28 Sep 2020 21:55 #184222 by machinedude
the initial error could point to backlash based on the direction your moving while setting up your tests.

an easy test for backlash is to just jog in incremental in the same direction a few times then set the indicator to zero. then jog in the other direction in incremental one time the other direction. if it moves the incremental value with no error then you are good if it does not move the incremental value then the difference of the indicator reading and the incremental value used is your backlash.

with backlash it would have repeatability running in a loop just no accuracy because of backlash. to me this sounds like what you are seeing on my first impression of what is going on by your description.

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04 Oct 2020 09:43 #184792 by RoberCNC
Replied by RoberCNC on topic Hybrid steppers or servos?

Since i have lost track of this topic, i am assuming you are using stepper motors and drives:
To avoid wasting more time, set the step space and step length to at least twice of what you have now or to at least 5000, set the dir stuff to 20000 and test again.
After that you can also set the microstepping on the drives to 1 and edit the ini scale accordingly, and just in case this fixes things that would mean that the drives have badly implemented microsteping or the motors are of very low quality.
If using closed loop steppers, the timing is the first thing to check.
In both cases, do not use microstepping with 1000 or 4000 or similar values, use the x16 or x256 values.


Obviously Tommy the steppers are the cause of all my ills so I wanted to change them, which was the initial topic of this thread. They are the first that I have bought in my life and I am paying for it, they are of poor quality, they are poorly calculated, dimensioned, etc ... Of course, everything I am learning is priceless :) :) :)
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06 Nov 2020 08:57 #188483 by RoberCNC
Replied by RoberCNC on topic Hybrid steppers or servos?
I keep mulling over the engine issue. Could it all be due to lack of torque?

It has occurred to me that the problems come because the motors are scarce, that they are fair for the dimensions and weight of the machine since I am more than convinced that it is at the beginning and stop of the movement when the failure occurs (or trajectory changes).

Makes sense?

Could it be solved with a 1: 2 pulley transmission for example? doubling torque at the cost of speed of course.

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06 Nov 2020 09:26 #188487 by tommylight
Direct drive for mills is a no go, even belts are not good for mills, but using some wide ones would still work with some lighter tolerances. Depending on what you intend to mill and the size of the end pulley, at least 1:3 to 1:5 reduction would be somewhat useable.
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06 Nov 2020 11:44 #188492 by RoberCNC
Replied by RoberCNC on topic Hybrid steppers or servos?
As always thank you very much Tommy.

Which transmission would be the ideal, which one do you advise? I think it is a travel and cheap idea to solve if it is a problem with the steppers (although I still want some servos hahahaha).

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06 Nov 2020 13:06 #188497 by tommylight
Since you have belts, use belt reduction.
Try to find "ideaformer1" on ebay, he has some small 1:3 reductions for 5$ a set, i did get some from him and they were nice, just do not expect to much from them as they are 6mm wide GT2 belts and pulleys.

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06 Nov 2020 13:20 - 06 Nov 2020 13:23 #188501 by RoberCNC
Replied by RoberCNC on topic Hybrid steppers or servos?
No, no, I have direct transmission from a spindle motor by coupling, the pulleys I ask how it proves by ruling out that they are the motors and the low torque. Try putting pulleys as transmission, I had thought of an HTD 15 mm wide.
Last edit: 06 Nov 2020 13:23 by RoberCNC.

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