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Auto Router On With Cycle Start
« on: September 01, 2009, 05:05:56 PM »
I am very new to CNC and am looking for feedback from the veterans. I am building a CNC router. I have the router connected to a solid state relay that is controlled by Output #1. I had planned to edit the g-code file to add the router on comand at the beginning of the file. However, why not use a Brain to turn the router on anytime cycle start is clicked? This should be no more "dangerous" than having the router power on when the command is embedded in the g-code. If I want to cut air as a test, I would disable the brain. Is there any reason not to take this approach?

Offline Hood

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Re: Auto Router On With Cycle Start
« Reply #1 on: September 01, 2009, 05:40:20 PM »
I dont like that idea, would catch me unawares sometime, I am sure of that. What I have is a real latching switch that is connected to the enable of my spindles servo drive and interupts the enable signal from Mach. That way any time I am near the spindle I disable it via the switch, you could do the same but just have the switch cutting out the signal from Mach to your relay.
I am presuming that is what you are wanting it for?
Hood
Re: Auto Router On With Cycle Start
« Reply #2 on: September 01, 2009, 05:53:32 PM »
My purpose for the relay is so that I can have Mach turn the router on when it starts a job. I had planned to put an M3 command at the beginning of the G-Code file to do that. However, rather than edit this command into the file, I thought why not have a Brain turn the router on for me anytime I perform a cycle start. The router has an on/off switch, so I will turn that off anytime I am changing bits.

If a person plans to start cutting anytime they click cycle start, then I think the Brain approach makes sense. However, in practical use, I did not know if people hit cycle start for other reasons. The only one I could think of is if you plan to cut air without a bit and without the router turned on. I imagine that is rarely done.

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Re: Auto Router On With Cycle Start
« Reply #3 on: September 01, 2009, 06:16:11 PM »
If you are the only person that will use the router then it should be fine, personally I would stick to convention and use M3/M4 etc but doesnt mean you have to :)
Hood

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Re: Auto Router On With Cycle Start
« Reply #4 on: September 01, 2009, 07:09:00 PM »
BAD IDEA, (;-) TP
Re: Auto Router On With Cycle Start
« Reply #5 on: September 01, 2009, 11:49:24 PM »
BAD IDEA, (;-) TP

Can you explain your thoughts on why it is a bad idea?  Do you use M3 now or do you manually switch the spindle on?
Re: Auto Router On With Cycle Start
« Reply #6 on: September 09, 2009, 01:44:03 PM »
I've got a nice spindle safety circuit. It disables the spindle if it is switched off, but importantly it can't turn the spindle on if it is released onto an otherwise "started" spindle; ie it can't ever be used to activate the spindle. Only M3 can start it. if M3 is called when the safety is "safe" then after it is released M5 must be called, and m3 called to start rotation. I don't have a circuit diagram but you can make it with two relays and a 2-way switch. Let me know if you can't see how and I'll draw up a circuit for you.

I don't think I'd allow a spindle to start off anything other than M3 or M4, it's just asking for trouble tbh. Careful ;)
Re: Auto Router On With Cycle Start
« Reply #7 on: September 09, 2009, 03:00:37 PM »
I have changed my plan.

My current plan is to only turn the router on using an M3/M4 command. I will then have a circuit issue a feed hold if router current is not detected with 1/2 second of the spindle on LED being true. That will catch the condition when you start the run and have left the router switch in the off position.

Thanks for the feedback.
Kent
Re: Auto Router On With Cycle Start
« Reply #8 on: September 10, 2009, 07:41:06 AM »
Sounds like a good plan :)

If you want to dry-run a program you'll need a lockout of some kind to disable the feed hold though. Shouldn't be hard to do.
Re: Auto Router On With Cycle Start
« Reply #9 on: September 10, 2009, 09:27:04 AM »
Sounds like a good plan :)

If you want to dry-run a program you'll need a lockout of some kind to disable the feed hold though. Shouldn't be hard to do.

I am implementing the control in a Brain. I can disable the brain to dry-run or I may add a button to the Mach screen that the Brain will read for disabling.