PLC and mechanical cams

[rogerhollingsworth]

mechanical cams

peterchy

I would be happy to assist in anyway I can.

At the risk of having someone suggest that you don't know what a cam is and have them give a ninth grade explanation, could you give a little more detail as to what you have and what you want to do.
I take your request serious and offer any help I may be able to contribute. Unlike some I assume you know what you are working with and if what examples I offer are not along the same lines then I suspect you would say so.
Don't let all the "OH LOOK AT ME, I'M SO SMART" posts scare you off, their are still some that really do want to help.

Keep posting.

 

[Jay Anthony]

Beware! Roger, I've been down this path before!
banghead

 

[rogerhollingsworth]

Beware

10, 4

Thanks

 

[Allen Nelson]

Roger:

It's great that you want to help, and I truly don't want to discourage you (I feel the same way - that's why I'm here), but this type of post is a typical student post.

Peterchy is a student, writing a paper on PLCs (the fact that he refers to them as "digital cams", and the broad-based nature of his request "give me some examples" bears that out).

He doesn't have a CAM that needs replacing, or has anything specific in mind. Somehow he's heard that PLCs can/have replace cams, and asked us to do his research for him.

More proof that he's a lazy-student type: This thread has been active for a week, and no word from him. His post count stands at one.

What he's interested in are examples. He might have in mind the old Tenor Drun units, like this one:

[attachment]

(image courtesy of PLCDirect)

which certain PLC instructions are designed to replace.

If I'm wrong, I'll eat Ron's virtual hat.

The best simple example I can think of is (and I can't believe I'm going to mention it), the

Traffic Light.

I remember an old McGuyver TV show where our hero chopped up a credit card, stuck the pieces into a traffic light drum controller, which caused traffic havoc right when he needed traffic havoc.

He did this while eating a chocolate ice cream cone and wearing a white suit. Brave man.

 

[rogerhollingsworth]

Student cam

Allen / All

You guys have been posting a lot longer than I have and can pick this stuff out and identify it, so thanks for the straight info. I will try my best to stick to the topic and stop telling others how to post. My mistake!

By the way that is the first one I ever made.

shutit Roger shutit

 

[Allen Nelson]

The Last Word?

Roger:

You didn't make a mistake this time, either. While some of us have a personal policy of not helping students, there's nothing wrong with throwing the poor pups a bone now and again. At least this topic was different.

And it can lead to all sorts of interesting tangents. Steve reminisced about headstands in hydraulic oil (yielding a brief foray into British slang), Terry reminisced about his days in the Navy (complete with commercial jingles of the time period - serious flashback there). There was a arguement/discussion about whether a cam is digital or analog (answer: yes). All-in-all, a typical thread here at PLCs.net.

We had one on the old forum that started with twos-complement, and wound up on Santa Claus, going through Norwegian, "subtrahend", and the usual name calling/insults. Now THERE was a thread!

It's all part of the give-and-take of a bunch of geeks who are good at what they do, and have too much free time/too little life.

Frankly, I like it (except the the no life part).

 

[rogerhollingsworth]

WHIP ME! & BEAT ME LIKE THE PUPPY I AM.

I LIKE IT!

 

[rsdoran]

OK good thing to put on my site, thanks for the picture Allen, it will come in handy.I have got to get a bigger notebook.

Anyway here is my contribution, as ususal it may or may not totally helpful but I think it may offer some insight.

Definition of cam:

An eccentric or multiply curved wheel mounted on a rotating shaft, used to produce variable or reciprocating motion in another engaged or contacted part.

NOTE: Coming from an automotive background I think of an engine cam shaft which has similar items used in industrial applications. I have several machines at my plant that operate via mechanical cams..no electrical involved except the motor that drives the shaft.

As time and machinery has evolved that kind of cam has been replaced with less mechanical devices that could initiate the same time of action. One of those devices is what Allen showed, a drum.

Definition of drum (non musical):
To bring about by continuous, persistent effort.
Something resembling a drum in shape or structure, especially a barrellike metal container.

NOTE: The similarity here is that each item revolves and at certain points an action is initiated

YES there are differences in the machines/devices that may or may not allow a PLC to replace the device that initiates the actions BUT I would say that in all probability any cam driven machine could be redesigned to use switches/sensors with a plc or some form of digital device.

BTW I remember the Santa Clause thing, that was in my early days when I pretty much became the most hated man here. My Santa Clause story was the best though. Roger as an aside these are some great guys but its easy to get into some heated discussions that can make someone feel about 2 inches tall, if you slip just a little they are all over you. Trust them, they know what they are doing, especially with the students. Not to say they may wont make some form of a mistake..did I say that?...but overall you cant find a better group to listen to or discuss subjects with.

SUBNOTE: http//www.patchn.com is coming soon. I plan to put 2 topics at the top of the list.
1. Electrical theory..primarily 3 phase
2. CAMS/DRUMS

 

[rogerhollingsworth]

In the steel plant we had boilers that had (huge)cam orerated systems on the pre-heaters, they have been in use for more that a hundred years and will probably be there until the end. No electrical involved except the prime mover, it would cost far too much to ever replace.

When I remove a defective operating switch from a substation and I read on the name plate "cam switch #xx-xxx-x, Westinghouse company", and I call the sales rep from Westinghouse and tell him I need a cam switch #xx-xxx-x and he sends me the correct item, then for all intent and purpose "THAT IS A CAM SWITCH". It would be pointless for me to argue. I guess you gota go with the flow.

If it walks like a duck and quacks like a duck..........

HUH?