Sometimes moves in the wrong direction
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The problem is that when I am doing manual jogging of the axis using the keyboard, sometimes it moves in the wrong direction and then it corrects itself. Other times I would have to unpress the keyboard and press it again to get it in the right direction. However, EMC2 thinks it has been travelling in the right direction all the time. This problem does not happen all the time, but quite often. I'd say 60% of the time.
For example, if I want to go right, I press the right key. However there are times the stage moves left first and then moves right. This incorrect movement is in the order of 1/8" (~3mm) and is quite visible.
Also, I think related to this, is that when I am milling a feature, the patterns drift along (so that 0,0 position is never the same and drifting). Essentially rendering my CNC useless. So, if I try to pocket a rectangle, the pattern drifts and I end up milling more on one side and less on the other as the mill takes sequential steps deeper into the cut, so there is a staircase on one side.
I am in the process of trying to eliminate what the problem is. Is it my controller, computer or some form of setting on EMC2.
Is there a reason you can propose for why it does this and how to fix it? Controller problem is one I am leaning on. Is there some setting I am not doing correctly on EMC2? Say timings of some form of setting? Position hold?
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It could be the accelleration settings, such that instead of the motor following steps 1 2 3 4 it is doing 1 3 2 4 (or similar) and running backwards.
As a first step I would divide the max speed and max accel by about a factor of 5 in the the INI file (or in Stepconf), and increase the step-time to 5000. If that helps, then you can start adjusting them back.
Also, try inverting the step pin. If you are using a parallel port and stepconf that is just a case of selecting a checkbox at the side of each step pin.
Which version of EMC2 are you using?
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John
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Mine is the sherline motor driver, and I was using the default sherline settings. I am running the latest version of EMC2 supplied by this website. I also tried customizing the stepconfig myself. The same thing happens regardless.
I never jog my stage too fast and I purposely tune the acceleration way down. I dont think it is the motor wiring? It comes stock from factory, and also it does move properly too, its just that sometimes it doesnt for the first portion of the motion.
My direction hold timings are the default ones, but Ive also played with them too to no avail. I assume too fast = small number, and Ive tried fast and slow. Im wondering, does it need to be optimized or a really long direction hold is fine, its just the milling is slower (this doesnt bother me as long as my CNC works first).
Any other possible settings? I also couldnt find more specific specs for the steppers or driver to input the best optimized settings. However Ive tried the default settings and my own settings, both run the motors smoothly and without resonance under my testing conditions.
EDIT:
I just realized from the changelogs it is up to version 2.4.7. My version is 1:2.4.3.1. The version that comes from the live CD. Is there bugs with this that can cause the problem? In any case, the problem occurs even with sherline's own live CD and using their version of EMC.
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You will probably never see the difference between minimal and super-long dir setup, as an axis is always moving at zero speed when you change direction.My direction hold timings are the default ones, but Ive also played with them too to no avail. I assume too fast = small number, and Ive tried fast and slow. Im wondering, does it need to be optimized or a really long direction hold is fine, its just the milling is slower (this doesnt bother me as long as my CNC works first).
As far as I know there have been no changes.I just realized from the changelogs it is up to version 2.4.7. My version is 1:2.4.3.1. The version that comes from the live CD. Is there bugs with this that can cause the problem? In any case, the problem occurs even with sherline's own live CD and using their version of EMC.
Can you halscope the axis position/velocity pins during jogging, and see if EMC2 is commanding the wrong move, or commanding the correct move, and getting the wrong move?
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Is backlash compensation turned on?
Can you change the pins / wiring from one axis to the other temporally to see if the problem stays with one axis or moves to the other?
Rick G
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The problem is that when I am doing manual jogging of the axis using the keyboard, sometimes it moves in the wrong direction and then it corrects itself. Other times I would have to unpress the keyboard and press it again to get it in the right direction. However, EMC2 thinks it has been travelling in the right direction all the time. This problem does not happen all the time, but quite often. I'd say 60% of the time.
That does sound more like an electrical problem like a loose connection or a bad driver board.
John
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How do I halscope to check this? On an unrelated note, I tried to update my EMC2 from the default version to the latest version 2.4.8, but I cant for some reason. I tried all methods, including git and updating with the tarball. It is still the old version, even though it created a new folder and everything. Wierd.
Backlash compensation is not on. I did try switching axis manually by unplugging and plugging another, and the problem follows the wire. Is it possible the motherboard of the computer is messed up? What about lack of power/current delivery to the motor driver (sharing the same power block with the spindle)? Im trying to think of everything.
Yeah I am heavily leaning on an electrical problem with the driver. When I switch the connectors over to another axis, that one messes up. What I also found was it goes from acting ok in the first few minutes of turning the driver on and gets worse over time when the driver gets warmer to the point of un-usable as a CNC. Then, if I were to leave everything on (EMC and all) and then swtich off the driver for 1/2 hr or so to cool down and turn it back on, it becomes fine again. I dont know if it is really a thermal issue, but definately over time it gets worse.
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That's a broad question. Have you ever used Halscope?How do I halscope to check this?
If you installed the new version from taball then compiled, then it probably installed as run-in-place and you can only start it from the command line, after running an emc-environment script that is in the dev directory under "scripts"On an unrelated note, I tried to update my EMC2 from the default version to the latest version 2.4.8, but I cant for some reason. I tried all methods, including git and updating with the tarball. It is still the old version, even though it created a new folder and everything. Wierd.
But I didn't know there was a 2.4.8
What I also found was it goes from acting ok in the first few minutes of turning the driver on and gets worse over time when the driver gets warmer to the point of un-usable as a CNC. Then, if I were to leave everything on (EMC and all) and then swtich off the driver for 1/2 hr or so to cool down and turn it back on, it becomes fine again. I dont know if it is really a thermal issue, but definately over time it gets worse.
This _could_ be a problem with the parport driver chips. Can you measure the direction pin current? Is it OK with jogging in the "zero" direction, but not happy in the "1" direction?
Many parports can only source 5mA, and some only 3mA. But most can sink 15mA.
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Do you mean the parallel port issue from the computer side or the driver side? Driver side? How do I measure the current of the signal without cutting the wire and running an ammeter in series?
Im not sure which is the zero or 1 direction, but yes essentially there is heavy bias on one direction when this happens. It only likes to move in a certain direction. It is essentially biased towards moving in a certain direction only, so it doesnt work both ways.
Do you mean the signal output from the parallel port from the computer is often 3-5mA and the parallel port from the driver can often accept 15mA? This is a closed black box sherline driver that I cant open without voiding warrenty so I dont know whats inside.
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