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Author Topic: Challenge question regarding Homing & Limit Switches  (Read 6697 times)

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Offline mhdale

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Re: Challenge question regarding Homing & Limit Switches
« Reply #10 on: April 23, 2007, 04:17:55 PM »
Poppa Bear, That looks like a pretty skookum Breakout board with some great features but I am not sure if it will solve my problem. I have 4 Separate motors on 2 of my Axis's which need to home properly.. so I need some way of disabling each motor as it hits home because they all share the same Step and DIR outputs and then re-enabling them to jog off the home/limit. Unless I am mistaken in what that particular breakout board will do, I dont think it gives me anything over what I have already. Basically pretend for some bizarre reason your x and Y axis have 4 motors on each and you need to be able to re-sync them back to home so they all line up... I know its sounds really bizarre but its what I have to deal with.... But thanks for the link looks like some great stuff there!

Mike

Offline poppabear

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Re: Challenge question regarding Homing & Limit Switches
« Reply #11 on: April 23, 2007, 04:27:32 PM »
Well from my understanding, you can set each axis to home count independantly (read that per motor).

If that doesnt work, then you could use a PLC.

i.e.   Put in your ladder that when you get the Homing routine, that it jumps to a homing "Stage", or just standard ladder. As the motors hit the switch, that the PLC picks up, the PLC breaks the power to that motor.  Then you "And" all the motor stopped outputs as an input, when all four have made it home, then the motors are re-enabled (pehaps you can put a timer here also), When the Re-Enable output signal activates, then it could also send this as a "Home" Signal to Mach.
The reason I say use a timer above is that, the moters will not re-enable until mach finishes sending its move off home switch signal, thus you motors will stay put, you can also "Time-out" your home switch, to fool mach into thinking that the motor have moved off the home switch, and Mach will "Zero itself there".

A DL 05 from ADC (approx. $100.00), would do the trick.  If you decide to go that route, but dont want to buy the programming software, then I could program it for you, (for a modest fee).

Scott
Commercial Mach3 & Mach 4, Design/Build/Retrofit CNC and Industrial machines.
http://www.ss-systems-llc.com/

Offline mhdale

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Re: Challenge question regarding Homing & Limit Switches
« Reply #12 on: April 23, 2007, 05:51:32 PM »
I am starting to think I may have to go PLC or microcontroller for the home.......

Offline GPDC

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Re: Challenge question regarding Homing & Limit Switches
« Reply #13 on: April 25, 2007, 03:11:18 PM »
FWIW dept....the hell w/multiple LS's.....that's a band aid for your set up....a nice fine thread jam nutted bolt (say the HEAD of a 1/2-20) with a squared end against a hard stop that is initially manually set by feeler gage & you're done.....the single limit switch per axis would then be mechanically " in sync" with all the other motors common to that axis' movement....periodic PM/QC would be all you need methinks...just a thought...would that be workable?

Offline mhdale

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Re: Challenge question regarding Homing & Limit Switches
« Reply #14 on: April 25, 2007, 03:37:27 PM »
GPDC The hard stop is the simple solution .. BUT the problem arises when the motor with the single limit switch hits the stop and limit first and lets say motor 3 still has a bit to go... the system thinks its squared but it really isnt.... You would need to go with 4 limit switches wired in series so the system will continue to drive the motors until they are all "bottomed" out against the hard stop.... It is the simple solution, for some reason a nagging voice in my head wont let me do it......sometimes my voice is right.. sometimes wrong.... The client is not very familiar with any automation equipment and I think might think less of us if the system makes whining chattering noises when it homes.... That is my current plan B should I be unable to implement one of the more elegant solutions...
Thanks for the input, I like to see what other people come up with!

Mike

Offline poppabear

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Re: Challenge question regarding Homing & Limit Switches
« Reply #15 on: April 25, 2007, 06:04:44 PM »
I thought of another way, if you don't mind doing some VB, and using the macopump.

You can make you a "Sorta-Home" button on your main screen, click this button, it runs a script, that will move each of your 4 motors at a set feed rate to your "Home-limit" switch.
Bring these individual inputs in, and the Macro pump monitors them, as each "Homes" (not a true home....yet), the Macro pump activates an output that cuts the Power to the drive of that motor.
These 4 relays will also be "Anded" together, once all 4 are homed (and power to all 4 motors are cut), then once again the Macro pump picks up that siganl then OEM codes the "Referance" command, (the signal is sent out for you motors to move/home but they wont since the power is off to them). In the Macro pump do a set timer(0) for some small value when it times out at value 1, have it "Activate the home input", then as mach "backs it off the switch" the second value for timer(0), will Turn OFF the "Home input for each motor" Mach thinks
it has moved off the home switch. In General config have Mach auto Zero after homing.
next, have the macro pump re-enable the motor relays, (Perhaps using a 3rd timer zero value, or some other interlock: Led, Dro or other logic that is testable).

Scott
Commercial Mach3 & Mach 4, Design/Build/Retrofit CNC and Industrial machines.
http://www.ss-systems-llc.com/

Offline mhdale

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Re: Challenge question regarding Homing & Limit Switches
« Reply #16 on: April 25, 2007, 09:53:00 PM »
Scott, If I didnt have so Many I/O to deal with on this system that would definitely be a good solution.  I am trying to hookup a MOD IO to get some more I/O but that comes with its own set of headaches.... I will definitely file that one away as a possible.
Mike

Offline poppabear

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Re: Challenge question regarding Homing & Limit Switches
« Reply #17 on: April 25, 2007, 10:40:27 PM »
In that case, I would definatly recommend a PLC, you need some intellegent I/O!!!!  The PLC can handle all of those functions on its on. Mach can tell it to start the process, and the PLC does the 4 axis homing work, then it sends a "done" bit, or home signal to mach.

Scott
Commercial Mach3 & Mach 4, Design/Build/Retrofit CNC and Industrial machines.
http://www.ss-systems-llc.com/