Ref: limit switches and inhibits


Much that has been discussed is ok for "Hobby" or home type machines.
As someone that retrofits drives and controls fora living I yet to
hear much about the real world issues of safety and "Safety
Standards".
The attached link is a 5 axis digital drive I completed last week and
every possible safety issue has been adressed.
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In large gantry machines like this, all axes drive motors have brakes
to ensure a quick stop in an error condition.
Soft over travel limits are set and deal with normal overtravel
condition and extreme overtravel result in a complete drive shutdown.
E Stops are handled by relays designed for this purpose.
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Not being critical but none of this would work in any real world
manufacturing plant.
db
Reply to
Dave B
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Looks very nice Dave. How *would* you do this in a real world manufacturing situation? (without adding additional limit switches, etc).
i
Reply to
Ignoramus31989
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All of the information and advice that has been given is right on target for your application.
I like the idea of dropping the drive out when you hit the overtravels.
Have the limit switches part of the E stop string and use a push button for an overide.
Hold the button down until you jog off the switch and then push the drive reset button and reset the estop string.
Sounds like you are on the right track !
db
Reply to
Dave B
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I would have three per axis +- OT and the home or reference switch. This are great to use very comapce and have cam rails with adjustable cams.
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db
Reply to
Dave B
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Particularly considering that the 5 limit switch and no brakes on the servos *was* a "real world manufacturing plant" design, though from a few decades ago.
The series2 Bridgeport knee mill certainly doesn't have enough mass or weight to need servo brakes, or hydraulic counterbalance on the Z axis as is common on the big iron.
I used to work on some big gantry machines back when and they certainly were a lot of fun. Not exactly home shop size though when they weigh 60,000#.
Reply to
Pete C.
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Actually it has a pneumatic support for the knee. It is not absolutely necessary, just a convenience.
I do not know about brakes, but the drives are four quadrant drives.
Reply to
Ignoramus11285
The video of the spinning machine was nice.
Wes
Reply to
Wes
Thanks Wes
db
Reply to
Dave B
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Wasn't the best choice of words just wanted to point out different ways of thinking and doing things.
After four decades of doing this I have seen a lot of different ways of doing the same thing. Some better than others.
Hopefully I wont have another decade of this.after awhile they all look the same.
Back under my rock.........
db
Reply to
Dave B
What video?
i
Reply to
Ignoramus11285
Retrofit I did with hydraulic servos
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db
Reply to
Dave B

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