Probe_basic Toolchanger

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01 Apr 2023 22:24 - 01 Apr 2023 22:28 #268038 by CNC_ANDI
Replied by CNC_ANDI on topic Probe_basic Toolchanger
Hello now i have a mesa 7i76e...

i see 2 options for me....

7i76e + 7i76 or 7i76e with Arduino

the second option is low cost. the first option will open more doors ;)

i´ve seen the 7i76e is available now.

but for this prototype we can try it to do with arduino.
Last edit: 01 Apr 2023 22:28 by CNC_ANDI.

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02 Apr 2023 01:29 #268040 by spumco
Replied by spumco on topic Probe_basic Toolchanger
Ok, arduino it is.

I have no idea how to program or control an arduino, so you're on your own with that.

The stock PB control scheme is a little complicated, but the basic platter/carousel motion works like this:
  • Toolchange.ngc
    • Do a bunch of stuff we don't need to worry about now, then
    • call M10
  • M10
    • Determines how many pockets (steps) are needed to move from the current pocket to the destination
    • Determines which direction to turn the carousel to get to the desired pocket
    • Write the number of steps to move down in a parameter
      • If CCW, call M11 and pass the number of steps as an argument (#P)
      • If CW, call M12 with same P argument
  • M11 (or M12) - Turn on a 'dumb' motor FWD (or REV)
    • While motor is turning, a sensor is triggered by a flag at each pocket
      • This sensor is connected to a digital input in LCNC
    • The M11 subroutine keeps track of how many pulses it sees from the pocket sensor
    • When the correct number of pocket pulses has been reached, turn off the motor
    • Write the new (destination) pocket number to a 'current pocket' parameter
This works because a geneva wheel permits the motor to overrun or underrun quite a bit while the pocket is locked in place by the mechanism.  Each time it's locked in an index position LCNC has time to read the pocket pulse from the sensor, M11 (or M12) has time to do the math and stop the motor.  If it rotates a little more than necessary that's fine - the pocket is still in position.

If you want to use an arduino and still use the stock PB control scheme then you may need to duplicate the motion of a geneva wheel.  That is, the arduino receives a 'ON/FWD' command and then:
  • Rotates the stepper the number of pulses between pocket centers
  • Stops the motor for a half second (or some time) while the pocket pulse is read by LCNC and M11 does the math
  • If the ON/FWD command is not turned off by the end of dwell period, rotate another pocket and dwell
  • Repeat until the ON/FWD command is turned off during the pause.
If you can program an arduino to do this you should be in good shape to move to some bench testing.

I suggest you get your prototype set up:
  • a microswitch or proximity sensor and install a flag (screw, bent sheetmetal, whatever) on each pocket.
  • A momentary switch for ON/FWD and another for ON/REV
  • Arduino
    • Programmed to move the correct number of steps between pockets
      • example: 8 pockets, 1.8 degree stepper, no gearbox (for testing), 10x microsteps
        • 200 x 10 = 2000 steps/rev
        • 2000/8 pockets = 250 steps/pocket
    • Programmed to dwell a second after each pocket even if the ON switch is held down
  • Stepper drive
Once you get that working, the next step will be to install a home sensor and a second flag (or a longer flag) on whatever pocket you want to be considered "home" or pocket #1.

Make sense?

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02 Apr 2023 01:30 #268041 by tommylight
Replied by tommylight on topic Probe_basic Toolchanger
Mesa 7i76E has two more IDC26 headers, each of those have 17 IO pins that can do high speed stepgen, encoder, PWM, etc.
Use those if they are free.

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02 Apr 2023 01:35 #268042 by spumco
Replied by spumco on topic Probe_basic Toolchanger

 test the carousel component with real hardware, and i have plenty of hardware so i can do stepper/position driven, DC motor driven, or whatever might be a good idea to try, also have a big box of sensors in all types and shapes.

 


Tommy,

The stock Probe Basic control scheme doesn't use carousel.comp.  All platter movement is controlled in the ngc files using parameters and motion.digital-out (or in) and motion.analog-out for the pocket number command.

My modified version of PB does use carousel.comp because I'm using a stepper in position mode - no geneva wheel - and I didn't want to treat the ATC as an axis.  Andy Pugh modified carousel.comp to send position-mode pulses to a stepper dive rather than treating the stepper as a velocity-mode 'dumb' motor.

The experimental version of carousel still needs some work (jogging doesn't work), but it's driving my ATC now.
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02 Apr 2023 01:40 #268044 by tommylight
Replied by tommylight on topic Probe_basic Toolchanger
Yup, i followed the development there, and that is the main reason i started thinking about making a TC.

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02 Apr 2023 02:43 #268047 by spumco
Replied by spumco on topic Probe_basic Toolchanger

Yup, i followed the development there, and that is the main reason i started thinking about making a TC.
 

I've collected every ATC example I can find on the forum and github. Rack, ATC-as-axis, carousel.comp, Classic Ladder, etc.

I don't have a double-arm ATC, nor do I have an example using an external controller (arduino, PLC, robot arm).  And I'm limited in my knowledge of programming GUI's to interface with ATC's.

When you're ready I'll be happy to help - it's the least I can do to reciprocate.
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02 Apr 2023 02:47 #268049 by spumco
Replied by spumco on topic Probe_basic Toolchanger

Mesa 7i76E has two more IDC26 headers, each of those have 17 IO pins that can do high speed stepgen, encoder, PWM, etc.
Use those if they are free.
 


What isolation - if any - would be used/needed for those IDC26 headers?  I've come across threads where PCW has mentioned using those pins, but I cant remember what the best way to physically hook them up to a drive (or other component for I/O).

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02 Apr 2023 10:01 - 02 Apr 2023 10:12 #268059 by CNC_ANDI
Replied by CNC_ANDI on topic Probe_basic Toolchanger
ok im thinking about that for one night....

so i think i will order a second Mesacard....

what do you say is the best doughtercard for my mesa 7i76e?

7i76 or 7i85s or 7i78

7i78 only have 4 more STEP/DIR Ports and 1 rs422
7i85s does have 4 More Axis, 1x Smartserial, 4x Encoder

or 7i76 for 4 more axis, 32inputs, 16 outputs, 1x rs422, 1x encoder

i think i will order the 7i76

7i76E+7i76

a homing sensor is already placed on my TC prototyp
 
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Last edit: 02 Apr 2023 10:12 by CNC_ANDI.

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02 Apr 2023 12:36 #268066 by tommylight
Replied by tommylight on topic Probe_basic Toolchanger


What isolation - if any - would be used/needed for those IDC26 headers?  I've come across threads where PCW has mentioned using those pins, but I cant remember what the best way to physically hook them up to a drive (or other component for I/O).

Using BOB is one way, although for wiring to stepper drives directly is OK as those have optos inside. I also used arduino relays on inputs and outputs, but this does require separate power for input relays to be fully isolated.
If using flat cable, use one gnd wire wound around every signal wire for anything longer than 10-15 cm. Helps with negating interference. There are 7 or 8 gnd wires, so i use one for every step/dir pair.

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02 Apr 2023 12:41 #268067 by tommylight
Replied by tommylight on topic Probe_basic Toolchanger
@Andy,
There is also Mesa 7i84, 32 in, 16 out, wires easily to 7i76E with a CAT5 or CAT6 cable.
Very nice for when you need IO.
I have the whole Mazak front panel wired to it, MPG and everything.

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