ATC Project - Debug phase

OMG this is turning in to a really dumb build/failure diary...

So the new plan is to manage the ATC like a rack-style changer.  Just found a great example of a rack changer (thanks GuiHue!) and need to translate the X/Y/Z movements in to a B-axis command.

Just as important: plopes9000 (of the twin-ATC, 5-axis TCP RF45 fame) has confirmed that he's using a rack-style, V&W-axes scheme for his awesome ATCs.

Manual testing shows the carousel behaves nicely as an axis.  Big closed-loop stepper means it's not painfully slow, and I get the benefit of an alarm if steps are missed (one less thing to crashy-crashy).

Question - can I define the axis as U/V/W even if I don't have an A/B/C axis?  I've disabled my 4th/A-axis at the moment (actually, robbed the stepper off of it), but the ATC is defined as "A" for initial testing.  Would like to set it up as "W" eventually.

Comments always welcome, of course.

Yes, you can have any sub-set of axes that you want. (lathes only have X and Z, for example)

I am trying to think how to make carousel work with your setup. With Gray-codes or similar it cold switch to slow speed when the code is correct and stop at the index mark. But if you only have an index mark, it's more difficult.
Does the changer overshoot all the way off the sensor?

Possibly adding a latch-velocity would work, and then have the carousel back off the sensor (or on and then off) at search speed, then make a slower aproach.

Does your current setup have a working Halcompile?

Or are you fed up of carousel now, and happy with toolchanger-as-an-axis?

Thanks for still giving this some consideration Andy.

The pin/flag will completely overshoot the proxy at higher speeds. At lower speeds it will stop at different places in relation to the proxy's trigger field.  Not to say it changes every time; rather a change in speed means a change in resting location.

Same-same both directions. Overshoot in the other direction as well as varying rest points after the trigger-decel sequence.

I'm not fed up with carousel, but I simply don't see how it can be made to work reliably without major changes.  If we step back and think about a carousel - or any tool changer - it is fundamentally a positioning device.  Precise positions has to be accomplished either mechanically or via position-mode control.  Geneva wheels, Chiron baskets, and ratchet-pawl mechanisms do it mechanically.  Side-wheel & arm ATC's do it with a combo (servo the drum, mechanical arm).  A velocity mode motor coupled to a non-mechanically indexed device with variable inertia doesn't result in precise indexing.

Adding a latch-velocity sounds promising, but it seems like a bit of gamble - what happens if the flag goes past the sensor?  It's the same problem as with LCNC's homing sequence.

If you want to make carousel more universal, then adding a position-control mode would be the ticket.  If the user chose 'mode X', then that would expose pins to set steps/rev.  Degrees per pocket would be calculated by carousel.  Essentially, it would take the math & direction logic out of the .ngc file and move it backstage in carousel.

I'm not wedded to the tool-changer-as-axis, but I'm moving down that road now.  Finding an example has been frustrating, but I stumbled across one last night that looks promising.  The issue with converting a true rack-style ngc file is that there are a lot of moves that don't equate to a position-carousel, nor is there any pocket-to-position math for me to steal.

If you want to fiddle with a position-mode carousel test, I'm completely happy to have a go at testing anything you throw my way.

Expanding on my earlier suggestion for a position-mode carousel... looks like simple_tp.comp would be the ticket.  Someone smart could edit carousel to output a position value (based on number of pockets) and enable-out signal, which is then sent to simple_tp, and then to the stepgen position command.

 

forum.linuxcnc.org/10-advanced-configura...in-linuxcnc?start=20
I am sure there is another topic with carousel and stepper lately, but i could not find it.

Tommy - there are a bunch of threads with steppers & carousel ATC's.  Many dozens... I've read them all over the past week.  All of them, hours and hours.  'carousel' 'umbrella' 'ATC' 'toolchanger' 'tool-changer' etc.

But they all are for Geneva wheels, ratchet-and-pawl turrets, or they don't have any config details or descriptions on how the toolchange.ncg handles the positioning & direction calcs.

There is exactly ONE post, from a user who only made one post ever, with a config for positioning-mode carousel changer.  He did not use carousel.comp - he did it as a B-axis.  Thankfully, he linked to his github page and it's still  alive with a readable hal/ini/m6.ngc config.

needle_in_a_haystack