I actually thought that said ONI. LOL
OK another minor milestone reached: I figured out the homing setup in LinuxCNC well enough to get a successful cycle test (dry run of a cut without plasma turned on).
Now I turn my attention to getting the height set right for the probing with floating Z, and the pierce height and cutting height, etc.
Looks like I’m running 16 micro steps / 1.5 amps.
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Yes, and my earlier read on how many amps you were running was way off because I was confused on which direction was on!
I now have my dip switches set exactly like yours as shown in your photo.
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My steppers might not like being run at 1.5A, that is a lot. We run the LR at .8 normally.
Well who knows with all the conversions that go on on the 2209’s maybe we are not at .8. The steppers can withstand up to a burst of 2.5A, but keep a real close eye on the temps. They will get hot enough to melt the printed parts in a hurry if you are not careful.
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For what it’s worth I’m running these steppers, I don’t remember how they compare exactly to what Ryan spec’ed back in '18. https://www.amazon.com/gp/product/B00QEYADRQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
My build followed @uthayne 's build (SOMD - Lowrider Plasma CNC), I upped the amperage based on his experience. I believe he mentioned back then that the extra amperage should help with faster accelerations that plasma calls for.
I’ve never really personally wrapped my head around stepper specs, curves, etc. @vicious1 is the expert, I say start with his recommendations and maybe tweak your way up if you have to.
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I’m switching to 1 amp and will see how it goes!
In another aspect of this, what should real world pierce height be? And what should real world cut height be?
Every machine is different, check your machine’s manual. If your manual doesn’t have any suggestions then as a reference mine suggests a pierce height of 0.15in (3.8mm) and a cut height of 0.06in (1.5mm). You could start there and fine tune with lots of testing.
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Thanks! You are the man!
I will check to see if my manual gives any help. I feel sheepish for not looking there first.
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Quick question about stepper direction and homing setup in LinuxCNC:
Are these three changes all equivalent, meaning they all accomplish the same end result?
- In the PNCconf setup wizard, select the “invert” checkbox option for step gen
- In the INI file, add or remove “minus” from the STEP_SCALE value
- In the machine’s wiring, flip the stepper wiring
Yes for the last two anyway. For pncconf make sure it’s direction and not step signal… I think
That’s three different ways to do it, only need to pick one though.
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OK, this part → “make sure it’s direction and not step signal”
…is an area where I still have confusion. Thanks!
I finally have a fully working, perfectly orienting homing setup and motion control system. It could probably be tweaked to avoid having to manually edit the INI file to remove minuses from the STEP_SCALE values!
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Re. inverting in PNCconf, there are two options:
Invert on TB3, where homing is done with INM inputs, and invert on TB1/TB2 for Step Gen-A.
I think I was mistakenly doing the latter instead of the former. Does the former change direction of travel? And if so, what does the latter do?
This is an area where I still have confusion.
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For TB1/TB2, step generators, I’d check the invert button next to the comboboxes that say ‘Dir Gen-B’ where needed. (it very well might work checking either ‘pin type’ but this makes the most sense to me intuitively)
For TB3, I’m flying by the seat of my pants here as I haven’t configured homing switches before. I could be wrong but I would think that inverting the switches here in pncconf just inverts the signal as presented to the linuxcnc software from open to closed and vice versa. I wouldn’t think intuitively that it has anything to do with homing direction. That said there’s plenty in linuxcnc config that doesn’t work in a way I would have thought to have been intuitive…
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Yes, you are correct about the inversion of switches. I had to do that on only my Floating Z switch.
When I was trying to invert the direction of stepper motors in the PNCconf wizard, I check marked the “Step Gen-A” option, but that seemed to get no perceivable result! So maybe it is supposed to be the “Dir Gen-B” box that needs checked.
Anyhow, I was able to make it where no inversions were needed in PNCconf and no manual edits needed in INI file, and I have a fully working motion control system, functional exactly as expected — pressing “-” goes toward left on X, toward front on Y, and toward downward on Z, and “+” does the opposite, exactly as hoped. The kicker for me is that my “home towards” choices in the PNCconf pages all had to be the opposite of what I was advised. Home towards positive for X and Y, and home towards negative for Z.
That reminds me: for a period of time when I was going through this an update broke this functionality in pncconf, the invert checkboxes did nothing for changing motor direction. The fix at the time was just to multiply the stepper scale by -1… Maybe it has been broken again?
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Could be! In any event, I got it all working great without needing the inversions after all!
