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Author Topic: Need a 7th Axis.  (Read 4994 times)

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Offline wil

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Need a 7th Axis.
« on: January 12, 2015, 08:40:09 AM »
Hi guys
All 6 axes in mach will be utilised but I also need to precisely control a worm screw to advance the pin tree 1.85 mm each time into a weld stage.
After welding, a cut off disc detaches the 2mm dia pin onto the welded component and preps the next weld face ready to advance.


I tried a timer which turns off the motor supply after the set amount of millisecs, but it never repeated well enough.
I guess maybe an electromechanical brake attached to a dc motor with gearbox ? and possibly have a sensor underneath the welded part to activate the brake on contact ?

any suggestions please.
Re: Need a 7th Axis.
« Reply #1 on: January 12, 2015, 09:04:59 AM »
I was reading your post thinking this is all above my head, but then looked closer at your drawing and wondered if you could use a Geneva Wheel to advance the pin tree.
Plenty of videos on the net showing how they work if you don't know what they are.
The motors stopping position isn't critical with a Geneva Wheel, it just simply needs to complete one turn to advance the pin tree and you could simply use Mach to activate a relay.

Offline wil

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Re: Need a 7th Axis.
« Reply #2 on: January 12, 2015, 09:28:07 AM »
cheers for that. I hadn`t seen them before.
I`d still need to control the motor position tho as it could stop mid cycle.
There could be as much as a minute or 2 between weld cycles while the rest of the machine does its thing. sorry I should have mentioned that.
Re: Need a 7th Axis.
« Reply #3 on: January 12, 2015, 10:10:25 AM »
You could just use a stepper (or servo) that has an "Indexing" type of drive.
Program a 1 revolution motion profile in the drive, then just call it when needed with a pulse on one of your available output pins.
The drive would then send an "In position" signal back to Mach when the move is completed and the program would then resume.
The Parker OEM 10 is a relatively cheap indexer that I have used with good success in similar applications.

Regards,
Russ
Re: Need a 7th Axis.
« Reply #4 on: January 12, 2015, 11:05:03 AM »
cheers for that. I hadn`t seen them before.
I`d still need to control the motor position tho as it could stop mid cycle.
There could be as much as a minute or 2 between weld cycles while the rest of the machine does its thing. sorry I should have mentioned that.

All you need to control a Geneva is a microswitch driven by a cam on the motor shaft that is open when the motor is in the "stopped" position.  Use a relay to short the contacts on the switch briefly, long enough to get the motor started and move the cam off the microswitch so the microswitch is closed and providing power to the motor, then open the relay.  When the motor has rotated about one turn, the cam should open the microswitch, stopping the motor.  That's the nice thing about a Geneva - it requires absolutely no precision control whatsoever to give very consistent, repeatable position.

Regards,
Ray L.
Regards,
Ray L.

Offline wil

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Re: Need a 7th Axis.
« Reply #5 on: January 12, 2015, 01:37:05 PM »
Russ, thanks a lot. That sounds exactly what,s needed, but i have had trouble finding a Parker OEM 10, if you have a link that will be appreciated.

I actually do like the Geneva plan from Ray, only thing i`m not getting is how to short the contacts breifly ? is that with a timer ?
Would it be possible to do it with a mach3 brain ? can you change a pin from high to low from a brain ?

The other thing with the Geneva thats getting me going, is i should be able to mount 4 cut off discs, driven off a central motor, and rotate them one at a time to do the cut off opp.
4 times the wheel life. those discs are only 0.030" thick.

I was considering going with Kflop for the 8 axis, but you guys have again showed me how knowledgeable you are and will find a solution to any issue.
Thanks again.
Re: Need a 7th Axis.
« Reply #6 on: January 12, 2015, 02:01:09 PM »
I'm sure Ray will get back to ya on ozymax's geneva idea, the timed output could easily be done with a simple macro.

I think the OEM 010 is way beyond obsolete. They had an OEM 650 later on, not sure if still avail or not.
Gecko is due to release an indexing stepper drive soon that would work very well .... any day now. You might inquire.

The Geneva is cool, but I'd prefer less mechanics. Just the smart motor, a belt with 2 pulleys.

Cheers,
Russ
Re: Need a 7th Axis.
« Reply #7 on: January 12, 2015, 02:35:17 PM »


The Geneva is cool, but I'd prefer less mechanics. Just the smart motor, a belt with 2 pulleys.

Cheers,
Russ

...... or, just directly coupled. Shaft to shaft.
Russ

Offline wil

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Re: Need a 7th Axis.
« Reply #8 on: January 12, 2015, 03:22:08 PM »
in this clip https://www.youtube.com/watch?v=7VDG7C5R5XQ he has attached an led via microswitch
I could do similar to activate the micro spot welder

Offline wil

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Re: Need a 7th Axis.
« Reply #9 on: January 12, 2015, 05:13:19 PM »
yikes
I just realized to rotate a 4 lobed plate one revolution, the motor drive has to rotate 4 times !
it would now also need a 4 to 1 gear train
« Last Edit: January 12, 2015, 05:21:02 PM by wil »