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Author Topic: Light curtain implementation  (Read 953 times)

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Light curtain implementation
« on: October 23, 2018, 04:19:28 PM »

Long time reader, first time posting, or asking to be precise.
I have learned so much on this forum, so i want to first and foremost thank you all for all the great discussions, and all the enthusiasm you guys have.
It is a great community and i am glad to become an official part of it.
Now on to the problem at hand.
I recently did a stud welder modification (still in progress) and i am asked to install a light curtain, machine already came with device SICK - FGS 300.
Long story short i need some assistance in setting up a stop, other than E-stop, i know how to implement E-stop but reseting each time after changing work piece would just be tedious,
on the other hand i need machine to stop movement, when light beam is interrupted.
In all honesty i have no idea how to approach this problem, on my parallel port breakout board i have 1 empty input, but i am not sure how to set the MACH3 to stop or prevent motors from movement, and also possibly prevent feed to proceed so DRO is correct.
I did search on the forum, and only found partial answer and it was hard to understand.
So if someone has any ideas, or helpful suggestions, i would be grateful


Offline Tweakie.CNC

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Re: Light curtain implementation
« Reply #1 on: October 24, 2018, 01:34:44 AM »

I understand what you want to do but before you implement anything you may wish to check the legal (and insurance) requirements, in your country, for machine operator safety.
Such safety measures as light curtains are often there to disconnect power and completely disable all parts of the machine if they are violated.

Re: Light curtain implementation
« Reply #2 on: October 24, 2018, 02:32:55 AM »
Thank you for the response.
I did check already, in order to better understand what i am attempting let me make a small diagram of parts, and try to show you why i need movement stop and not power disconnect:


i forgot to mention this is a rather small table top CNC
so powering it down would be overkill, it is positioned on a desk that is pushed against the wall on the back side, but i hope diagram will explain better, and yes it was made in paint :D
i am one of those people ;)

Thanks in advance
« Last Edit: October 24, 2018, 02:45:33 AM by xpozec »
Re: Light curtain implementation
« Reply #3 on: November 06, 2018, 06:46:56 AM »
I am back with an update,

Figured it is not smart to do feed hold, but decided to go with E stop.
So i did some adjustment to the electronics, set it up in a way that light curtain is always active, however only when machine is working is E stop in play,
the way i did it is, used one of the outputs from BOB to activate AND part of the solution.
Used Flood relay to activate AND part and adjusted PP accordingly.
Problem i have now is, when E stop is activated, it turns off MIST/FLOD relays, is it possible to prevent this in any way?
Basically is it possible, to set up program when E stop is activated one of the outputs remains in a last state: if off than off; if on than on;

I did some googleing, and found someone asking the same question, but when i use the link, it redirects me to index page of the forum
Any help would be greatly appreciated, thanks in advance
Also when it is ready, i will post the video of machine working, not too many STUD welders in video section.