Need a little help

dalebartelds · Dec 3, 2005

I am just starting out with PLC programming and would like to ask for help. I have a machine that welds a clip onto a part that already has a nut on it. On this fixture I have a sensor looking for the nut to be on the part. Also I have another sensor to make sure the clip is in the fixture and lastly I have a sensor that makes sure there is only one clip under the part.

Right now if any of these sensors do not turn on the welder will not weld. The problem comes in when one of the sensors becomes shorted on all the time because of weld splatter. The operator will continue to weld parts sometimes without the clip being in place.

I want to use a PLC to make sure each of the three sensors turns on and off with each stroke of the weld cylinder. I've mounted a sensor on the cylinder so I am able to tell when it moves.

I have an Allen Bradley Pico to work with and I've read some of the tutorial. I sure would like a little help getting started.

Thanks,
Dale

stasis · Dec 3, 2005

well, a Pico isn't exactly a PLC...it's more of a smart relay. The Pico doesn't do sequencing, which sounds like what you need to complete your task.
Which type of Pico do you have, and do you have the software for it, or were you planning to program it from the face of the device?

Steve Bailey · Dec 3, 2005

A simple fault detector would be a timer for each of the three sensors. Start timing when the sensor goes ON and reset the timer when the sensor turns OFF. Select a preset for each timer based on how long each sensor should be ON in normal operation plus a little margin. If any timer's done bit comes on, that's an indication of a fault.

lanman · Dec 3, 2005

Besides monitoring the sensor for an always on condition, you should also be using a spatter and weld field resistant prox.

alielectrical · Dec 4, 2005

I presume that every time a part is placed in place and then removed after welding is complete.
I suggest checking all sensors to be ON before the welding cycle and then check for all sensors to be OFF when the part is removed after welding. This makes certain that the sensors are working properly.
I hope this helps.

Lancie1 · Dec 4, 2005

Dale,

I uploaded the Pico software, and wrote you a little program. It was too big to display as a picture.

dalebartelds · Dec 5, 2005

Thanks for the reply. I would like to use the 1760-L18 because I already have one. I know the software is a free download on the web and I think there is a laptop or two around with it already on it. But isn't it possibale to just use the screen to program it?

dalebartelds · Dec 5, 2005

One of the problems is I only have enough room for a 5mm prox. I have not been able to find a weld splatter immune sensor that size. Balluff sells a ceramic face (604094) you can glue on the face of the prox that might help, I am trying that now but I still want to monitor the sensors.

dalebartelds · Dec 5, 2005

Lancie1, Thanks for the drawing help. It gives me a good start. I'm not sure about the timers though. I think I would like to tie somthing into the stroke of the welder using the sensor I have on the cylinder. If I place the sensor half way up on the cylinder I should be able to see the cylinder as it goes up and then again when it comes down. I was just thinking maybe I need two sensors on the cylinder and then then I will know for sure where I am in the stroke.

p.cooke · Dec 5, 2005

I am p.cooke. SEND me $1000 and i'll fix your problem. untill later

CaseyK · Dec 5, 2005

Got Pasion?

p.cooke said:
I am p.cooke. SEND me $1000 and i'll fix your problem. untill later

Sounds like a bargain! 'Specially after this post on another thread.

leitmotif · Dec 5, 2005

Originally Posted by p.cooke
I am p.cooke. SEND me $1000 and i'll fix your problem. untill later

Sounds like a bargain! 'Specially after this post on another thread.

Well at least he is self assured and confident

Dan Bentler

Mickey · Dec 5, 2005

Fred Floggle meet p.cooke

jpayne · Dec 5, 2005

I know you have counters in the Pico controller. If the Pico supports a compare instruction, setup a counter for each of the sensors. Compare the counter acc. If the values are different, one of the sensors is not reading correctly.

CaseyK · Dec 6, 2005

leitmotif said:
Well at least he is self assured and confident

Well Dan, with him around, the rest of us can take a vacation and be well asured the site is in good and capable hands!

So, everyone gets the rest of the year OFF WITH PAY!

Seasons Greetings.....casey

Need a little help

dalebartelds

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stasis

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Steve Bailey

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lanman

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alielectrical

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Lancie1

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dalebartelds

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dalebartelds

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dalebartelds

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p.cooke

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CaseyK

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leitmotif

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Mickey

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jpayne

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CaseyK

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