Keeping track of bottles to be ejected

[Eric Nelson]

Welcome to Page 2...

I had thought to just eject everything off on power-up until I reached the first bottle that I checked, but could not get that to work right either.

That part 'should' be fairly easy. Whatever device you use to 'track' the bottles can just be filled with 'failed' bits/words at powerup. For instance, if you're using a shift register, with a value of 1 representing 'passed' inspection, and 0 (zero) representing 'failed' inspection, just fill up the shift register with zeros at powerup. You could just make the bits (or words) non-retentive and they'll automatically go to zero with no power.

Too bad you can't do the inspection and reject while the bottle are still in the labeler's timing screw. Once they leave the screw, you lose that control. The phrase "You're screwed" comes to mind (actually, that fact that you're NOT screwed is the problem)...

This project may be slightly advanced for a beginner, but it's definately a worthwhile learning experience!...

beerchug

-Eric

 

[Hootnholler]

Hey Bob,

Now I have a slightly better idea of what you are talking about... where I work, we usually check the bottles after the filler (which runs from 800 to 1600 bpm), so was not aware that you were checking them after the labeler...

The labeler will actually help. I like Lancie's idea of using all the tools incorporated for your program. We use a similar setup off our labelers. Plus, I'm guessing that you have to do a program change on the labelers whenever you changeover, so how about setting up some outputs from the labeler plc to the ejector plc vs. the program? Will that help at all for the varying bottle sizes? Plus, it may help with the minimal amounts of work per changeover (I'm all for that, done enough in my time...).

As for Eric's post of you're screwed (gotta love Eric, needed that laugh... lol) that will actually help you with the spacing as it comes out of the labeler. As you posted, you will have a problem from time to time dealing with down bottles, etc... but I feel that would be able to be fixed by the operator. Make it so it works under optimal conditions first, then work some safeguards in as you go. Once you have a working program, it's easy to amend to the needs of the people.

Good luck with your project and keep us posted on how it goes!

Hoot

 

[93lt1]

Re: Welcome to Page 2...

Welcome to Page 2...

My "preferences" must be different than yours...

 

[Eric Nelson]

And what page might YOU be on 93?...

I figured the BBS paginated the threads based on thread size (and by 'thread size' I don't mean like 1/4-20!)...

I didn't know it was 'selectable'...

beerchug

-Eric

 

[Eric Nelson]

Well I'll de darned...

Hmmmm, it seems you CAN set the page length. Ya learn sumptin' new evry day!...
[attachment]
beerchug

-Eric

 

[Buhsman]

Lancie1's post is just about exactly the way we do it where I work except we use an encoder to measure the distance. We have to be very accurate on our blow off timming because we are running about 2000ppm. It removes the correct part with almost 100% accuracy.

 

[shooter]

that is the one

STEP 1: You attach a pulse generator (or Encoder but much more expensive) to the conveyor, usually to the main conveyor head shaft. The pulser is calibrated to generate an "on" bit every time the conveyor moves a certain distance. I usually use 1 inch. Note that the pulser can be nothing more than a proximity switch with a target attached to the conveyor shaft at the right length. Now when your photosensor detects a bottle passing, you insert the first "1" bit into your shift register, BUT EACH SUBSEQUENT SHIFT IS PERFORMED IF AND ONLY IF A PULSE IS RECEIVED FROM THE CONVEYOR PULSE SWITCH. This way, you can measure with a tape (only 1 time) how far it is from the bottle sensor to the EJECTOR PHOTOSWITCH. Your bit (representing an individual bottle) shifts up to a number that equals the MEASURED DISTANCE MINUS SOME ERROR FACTOR (a known constant number). The error factor is set so that no matter if the bottles slip a little, that the next bottle down the line will the one being tracked. In other words, if your bottles are spaced about 6 inches apart, your error factor could be as large as 6 inches. The idea is to bracket the bottle within a certain range


this is the solution
on the conveyor chain make a pin and have a sensor on it.
this will count the distance.
use a shift register and if 1 put air on
you can use another counter to have the air on for longer.
if need more help just give the hardware and we will make program

 

[93lt1]

I found it by accident, long ago...

Hmmmm, it seems you CAN set the page length. Ya learn sumptin' new evry day!...

Yes...

 

[Dartrunner]

Thanks for the help!

I think I have it programmed the way Lancie1 explained it and have to wait till Sat. to give it a try. I am using a UHMW plastic wheel attached to the drive shaft with 20 bolts in it being sensed by a prox. Looks like it equates to about 1 in distance of belt travel between bolt heads. Anyway, will hook it all up Sat. and will let ya'll know how it turns out.

Thanks for all the help!

Bob Smith

 

[tomneth]

kewl

It sounds like it should be a reliable way to do the job. Pretty clever idea using the bolts in a plastic wheel! Just make sure the wheel is attached to the drive shaft in manner that won't allow the wheel to slip. Good luck to you.

 

[David_Emmerich]

After 10 years as a Single Line mech in a glass plant, and 10 more as plant engineer in a pet bottle plant, the most reliable way is to have the container in positive control from inspection point to reject point, even if that means adding another screw or timing wheel...better yet, but not always practical/possible, is to reject it as soon as it is declared a reject...Another way is to dab the top of the reject bottle with a colored mark, at the inspection point, or points, and then set up a color mark detector somewhere down stream to reject all the defects at one point. We often used this on clear glass bottles...did 5 to 10 inspections on the bottle, but only had one or two cullet chutes.
Some times I think that we all need to think KISS.....do we really need to run that thru the PLC?.... Don't get me wrong...I put PLC's on some Darned simple things, just to make them more Op frendly or to keep the Op from ruining things by getting them out of sequence. But there are some really basic ways to remove defects that are tried and true... now as far as collecting data on how many are rejected where and why and when having a PLC on line sure beats a mechanical counter and a pad and pencil!!!!
beerchug
David

 

[Dartrunner]

Labor Reduction

The main reason we are doing a lot of this stuff is labor reduction. Now we have 1 mechanic, 1 line servicer, and 8 line workers on each line. Our goal is to get down to 1 line mechanic and 3 line workers per line. So you can imagine how popular myself and the team trying to do this are. At the same time we are suppose to cut changeover time in half. We have been able to automate 3 jobs so far, and we have already reduced change over time from 6 hours to 4 1/2 hours in 6 weeks. Of course we tackled the easy and obvious stuff first. I think it is going to get harder and a lot more expensive the more we do. Most of this is driven from patent expiration and generics moving into the market. As the automation gets tougher I might be asking a lot more questions, so far the first one has had a great response!

Thanks everyone!

Bob Smith

 

[Dartrunner]

It's in and working now!

I had a few minor programming errors and one big common sense problem. The big problem I had was that I used socket cap screws in the wheel to be sensed by the prox switch. Well, sometimes the prox picked up the socket hole, and sometimes it didn't. Took me about 4 hours to figure out what was going on. I kept looking for a program problem.

Anyway, thanks for the help, ya'll sure made me look good!


Bob Smith