Preparation for the self-construction of a carousel changer

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02 Jun 2022 14:56 #244454 by mgm
In the last few days I have been trying to get some knowledge on the subject of a tool changer.
I have imagined the following:
- 12 station carousel changer with geneva wheel
- index positioning
- retract / extend to the change position of the changer with pneumatics


But there are still some questions where I found no answer for me.
- is it possible to drive a geneva wheel with the carousel.comp?
- stepper motor or brushless DC motor ?
   (stepper motor NEMA 23 with 3Nm would be available)
- what hal pin is required for the carousel.comp to work ?
  minimum requirement !
- which prerequisite is needed that I can e.g. put tool no. 5 in pocket 11
  can put?

is there anyone who already runs a geneva wheel with the carousel.comp ?

I am grateful for any help or explanation.
 

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02 Jun 2022 15:26 #244457 by spumco

In the last few days I have been trying to get some knowledge on the subject of a tool changer.
I have imagined the following:
- 12 station carousel changer with geneva wheel
- index positioning
- retract / extend to the change position of the changer with pneumatics


But there are still some questions where I found no answer for me.
- is it possible to drive a geneva wheel with the carousel.comp?
- stepper motor or brushless DC motor ?
   (stepper motor NEMA 23 with 3Nm would be available)
- what hal pin is required for the carousel.comp to work ?
  minimum requirement !
- which prerequisite is needed that I can e.g. put tool no. 5 in pocket 11
  can put?

is there anyone who already runs a geneva wheel with the carousel.comp ?

I am grateful for any help or explanation.

 


Yes, you can drive a geneva wheel with carousel.comp.  That is the fundamental mechanism carousel was designed for (I think.  You'd have to ask the developer to be sure).

Yes, stepper or BLDC works.  carousel.comp can be set up to control the motor with FWD/REV relays (dc motor, ac induction motor, BLDC), or with a velocity-mode step generator (stepper or step/dir servo).

Carousel hal pins are created when carousel.comp is loaded in the hal file.  Additional pins used include motion.digital-in-NN and motion.digital-out-NN to activate the motor(s) and air cylinder solenoid(s), as well as transfer signals from sensors (index/pulse/retract/extend/drawbar) to carousel pins.

Doing the tool #5 in to pocket #11 is do-able, and is called a 'random' tool changer.  The axis-vismac-sim configuration doesn't have this feature, but I've run across multiple configs posted in the forum using this feature.

There are buckets of people already running carousel with geneva wheels.  Suggest going to the forum advanced search page and searching for 'carousel.'  Limit the search to 'thread title only' and you shouldn't be overwhelmed with 10 million hits. 

Unfortunately, there isn't a really great high-level description of automatic tool changers in the manual(s).  All of the different things you need to know are in there or in the forum, but they're mostly scattered around and you'll feel like an Easter-egg hunt compiling your mental understanding of 'how it all works.'

Plan to do a lot of reading.  Take notes.  Make a list of all the different ways people are controlling tool changers and see if you can find examples of them (gcode/.ngc, classic ladder, external PLC, etc.).  Tool Changers are not really a plug-and-play thing in LCNC for new users, so you're in for an education.  Like just about everything else in LCNC, once you've accomplished something it becomes obvious... but until then it feels impossible to understand.

If I ever get mine finished, I'm tempted to try writing an Idiot's Guide to LCNC Tool Changers document to be added to the official manual (or somewhere), along with known working configurations (with simplistic explanations).

I know, having recently read through hundreds of forum posts, that everybody seems to go through this miserable trial-and-error Easter egg hunt to set up an ATC.  How much time is wasted for lack of an overview guide?
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02 Jun 2022 16:06 #244461 by tommylight

If I ever get mine finished, I'm tempted to try writing an Idiot's Guide to LCNC Tool Changers document to be added to the official manual (or somewhere), along with known working configurations (with simplistic explanations).

That would be nice, although given the variety of hardware in use, it is not going to be easy.
Still, a general direction should be good.
-
Rant:
My first toolchanger took a whole day till i found ArcEye 's configs, after seeing that it took about 2 minutes to have it moving and another 4 minutes to have it properly set.
Second one, 16 pocket umbrella, used carousel and for over 3 hours nothing, not a single move or beep or f@rt, nothing, went to bed, next morning a quick glance and ... oh shame, one of the lines still had # in front of it! :)
When nothing works, take a break, do something else entirely, go grab a coffee, then come back to it.
EOL
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02 Jun 2022 18:09 #244467 by spumco
Let me know when you get up to 10 days of beating your head against the LCNC tool-changer wall, and we'll compare notes

And yes, my thought is a general overview with a description of the various mechanisms, motion hardware, and control schemes - along with a basic description of what the end result looks like in HAL/INI/Ladder for the combinations.

It can't be that hard.  I'll just write what little I know, submit it as 'gospel' to the forum, and everyone will jump on me pointing out all the important things I left out.  Update and resubmit; easy-peasy.
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02 Jun 2022 21:51 - 02 Jun 2022 21:54 #244473 by tommylight

It can't be that hard. I'll just write what little I know, submit it as 'gospel' to the forum, and everyone will jump on me pointing out all the important things I left out. Update and resubmit; easy-peasy.

Oh you sneaky .... :)
-
That was meant to show that after a day of banging the walls with the forehead and reading anything and everything remotely related to it, it was easy to set up. But only after banging .... :)
Last edit: 02 Jun 2022 21:54 by tommylight. Reason: more info
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06 Jun 2022 08:32 #244658 by mgm
First of all, thanks for the encouraging words on this topic .....
My headaches are still lingering a bit, but it's slowly dawning on me how it might work.
There are still a lot of uncertainties though!

For example:
I can use dc motor or stepper to drive but which is better or easier with a geneva wheel?

Do I need to send both types of motors home at the beginning?

Is it better to have a position feedback on each tool pocket (gray coded) on a geneva Wheel or is an index and a sensor on each tool pocket enough?

Once I have that answered for me I can get the appropriate parts and build the changer.




 

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06 Jun 2022 13:46 #244664 by tommylight

Is it better to have a position feedback on each tool pocket (gray coded) on a geneva Wheel or is an index and a sensor on each tool pocket enough?

 


I would go for gray code.
Not an expert on tool changers, just my thought after dealing with both types.

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06 Jun 2022 15:14 #244675 by spumco

I can use dc motor or stepper to drive but which is better or easier with a geneva wheel?

Do I need to send both types of motors home at the beginning?

Is it better to have a position feedback on each tool pocket (gray coded) on a geneva Wheel or is an index and a sensor on each tool pocket enough?

Once I have that answered for me I can get the appropriate parts and build the changer.

 


If you're going to use the carousel.comp tool changer component, either motor will work fine with a geneva wheel.  The DC motor may be cheaper and easier to implement (couple of relays) unless it requires an odd-ball power supply.  If you use a stepper and it's the same input voltage as your axis drive motors, then the PS is taken care of.

Again, carousel.comp will auto-home the carousel the first time it's enabled each session of LCNC.  If you use something other than carousel.comp, you need to have some method of establishing pocket location/number when LCNC starts up.

Depends on your preference.  Gray-code provides pocket number feedback for a safety-check, but requires the mechanical and sensor setup.  Index & pocket-pulse are arguably cheaper & easier but do not provide pocket-number feedback - only that the carousel is at a pocket.

In addition, there is a new(ish) version of carousel.comp which only uses a single index pin/sensor and a stepper (or servo) motor; no geneva mechanism required.  This version isn't in the official LCNC distributions yet, but it uses the stepgen encoder output as a feedback device to carousel.comp for position calculation.  Simplified: you tell carousel.comp how many steps between each pocket, and it both commands the motor to move and counts the stepgen pulses during the move and stops at the right position.  Works pretty slick, no mechanical indexing hardware required.

I'm in the - hopefully - final stages of building a setup like this with a stepper and 5:1 reducer.  No belts or geneva mechanism.

If this sounds interesting, have a look at my "ATC Project..." thread.  If you wait a little bit I'll be doing further testing & refinement over the next few days (weeks?) and will report back how it all goes.

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07 Jun 2022 06:36 #244710 by mgm
Hello Ralph,

again very detailed answer to my questions, thanks for that.

I have been following your reports on this topic for a long time. They are always very informative.

Since I already have a geneva wheel I will also implement.
The position recognition with Gray-code is also set and I have now ordered a Nema23 brushless DC motor 57BLF02 with driver.

Michael

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07 Jun 2022 11:29 #244717 by spumco
Sounds like you're in business.  Geneva wheels and DC motors are robust - nothing wrong with them besides wierd acceleration.

Should make for a pretty easy/standard control setup for you.  I'm finding this part of the ATC thing much more painful than the mechanical.

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