Material output per time for speed test question

ElectricFreak

Member
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Join Date
Dec 2009
Location
Indiana
Posts
26
Hi All,
I need to calculate total material output per X time for a production machine.
To put it another way, I need to know how much material weight the machine put out in the previous 5 minutes, continiously.

This machine outputs material in bags at varying weights.
Its fastest output is 1 bag every 7 seconds, but varies because it is operator controlled.

My original thought plan was something like the following:
1: load the bag weights and their output time into a datatable or where they are tied together.
2: keep a running total of them and continiously delete the entrys older than 5 minutes.

it always sounds simple until you get to the details.

I am presently reading the bag weights in floating point.

My problem is I do not know how to tie the weight values to the time, and where to save them.

Is this possible to do within a SLC 5/05, and how should I do it?

I can purchase any devices or equipment that are required to get this accomplished, but I would prefer to use what I have if at all possible.

Thanks in advance for any suggestions.
 
Stop watch and a counter gizmo? After all you said it was only for a test - I assume for a short time so why bother doing all the programming for a single shot evolution?

The more I see of this output number stuff the more I think an speed limiter should be emplaced to keep production from running teh poor thing at 110% speed to catch up.

What really bugs me is after a month they ignore it because they found it was a useless statistic.
Dan Bentler
 
It's called a speed test, because that is its purpose. this is not a one time or temporary test.
This test is already done several times per day now, pretty much just as leitmotif described, with a stopwatch and someone recording the weights on paper.

but this requires the production to be stopped at the start and end of every test, and a lot of hand calculations.

Crude yes, but I am attempting to improve the process.

This test has nothing to do with pushing the people or process, its purpose is to maintain a consistent and safe product.

The output(speed)value (in lbs/min) is compared to the already known amount of chemical used per minute to verify that proper fire retardancy is acheived.

Maybe I should call it something else, but that is what the production team calls it.
Chris
 
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OK so the test is required to meet legal reqs. I dont see why you need to stop production - in my mind I would do test random during a production run without any changes in the run - after all it is supposed to ensure product quality.

What are you doing mixing a retardent in with a product or spraying it onto a fabric? I assume mixing because product is sacked.

Given that I think the best way of course is to pull a grab sample and measure chemically. That would verify that the PLC program (following) is operating correctly

I would
1 set time ZERO
2. measure weight of component A
3 measure weight of component B
THEN after some time interval
4 get new time
5 weight of A
6 weight of B

then calc A2 - A1 divided by T2 - T0
and same for B

Now you have weight and if you want volume of A and B used over a time period From this you can compute percent A and B.

Now that you ahve the number then what to do with it? You need to dump that to a computer for recording over posterity.

Dan Bentler
 
Electric Freak,

I'm not sure I understand what you are wanting. If I read you correctly you basically want a rate meter. This meter would display the total weight bagged in the last five minutes and would be updated every second. Or maybe I got it all wrong. Maybe you want something that someone could push a button and get a total for the last five minutes. Give a few more details and perhaps someone can help.
 
Ok, The product is cellulose insulation, made from recycled ground newspaper, and fire retardant chemicals.
The paper is impossible to get an exact flowrate per/lb because it changes according to what wood it is made from, its moisture content, its density, etc. there are many many unknowns in recycled paper.

The only way to know the product was made correctly, is to know the weight of paper that was used, and the weight of the chemical, during the measured time.
This has to be calculated by subtracting the chemical output from the total output.

I know the weight of the chemicals used, because they are metered by flowmeters in lbs/sec. Their output is verified on a regular basis.

So to answer your reply, There is no known method of measuring component A (ground paper flowrate) in a continious run situation.

Production must currently be stopped to verify the product hoppers are at the same level for the start and stop of the test.

There is nothing perfect about this process. I have tried for 8 years to improve it, and the production methods.

Unless someone can tell me how to measure ground paper in a flowing pipe that averages 600 pounds per minute, I cannot change the way it is made now.

I have been beating my head against this mess for years, and I did not setup this operation.

I sincerly appreciate all comments, but I simply want to know if my original plan is possible, and how to do it, with any equipment?
 
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ElectricFreak said:
Ok, The product is cellulose insulation, made from recycled ground newspaper, and fire retardant chemicals.
The paper is impossible to get an exact flowrate per/lb because it changes according to what wood it is made from, its moisture content, its density, etc. there are many many unknowns in recycled paper.

The only way to know the product was made correctly, is to know the weight of paper that was used, and the weight of the chemical, during the measured time.
This has to be calculated by subtracting the chemical output from the total output.

Production must currently be stopped to verify the product hoppers are at the same level for the start and stop of the test.
Unless someone can tell me how to measure ground paper in a flowing pipe that averages 600 pounds per minute, I cannot change the way it is made now. quote]

Hmmm well I can at least understand the difficulty. I assume you grind the paper then pneumatic convey at 600 lb/minute then mixed with no storage bin in the middle?

How do you know the 600 lb/min value?

how do these hoppers fit into the setup - are they done only for the test and not used rest of time?

How long to setup for the test?
Dan Bentler
Click to expand...
 
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Leitmotif, you are correct on the pneumatic convey

We have measured the paper output a few times. it varies between 450 and 700 lbs/min. Many variables here!

The hoppers are always in use, and when things are running at maximum, they stay at their lowest allowed level.
I accept that this test will never be perfect.
it is not perfect now, as I could easily pick multiple errors in it.
But it is as perfect as anyone here knows how to do at this time.


The test time I will have to adjust to accomidate the values until a stabil number can be reached.

The tests usually last for 10-15 mins. But my goal is to make them happen automaticly and constantlty updating.
Please forgive my incorrect spelling.
 
ElectricFreak said:
Leitmotif, you are correct on the pneumatic convey

We have measured the paper output a few times. it varies between 450 and 700 lbs/min. Many variables here!

The hoppers are always in use, and when things are running at maximum, they stay at their lowest allowed level.
I accept that this test will never be perfect.
it is not perfect now, as I could easily pick multiple errors in it.
But it is as perfect as anyone here knows how to do at this time.


The test time I will have to adjust to accomidate the values until a stabil number can be reached.

The tests usually last for 10-15 mins. But my goal is to make them happen automaticly and constantlty updating.
Please forgive my incorrect spelling.
Click to expand...

Onli if you ate tolerand of my tipos

Worked at a plastic extrusion outfit used hoppers and weighed them to measure flow of plastic in terms of lbs/time.

you say you have hoppers. Could you fill one then switch to empty mode ie convey to mixer and measure the time to empty - in meantime the other hopper(s) are filling. Granted this will require another blower and valves maybe and will cost energy because you slow the paper to a stop and then have to reaccelerate it but it may be an option.


Dan Bentler
 
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Hey,
the machine only has 1 hopper.
a major problem is the super low density of this product makes it incredibly difficult to measure hopper level, with any reliability.
It would be much easier to measure the level of a hopper full of styrofoam peanuts, than this stuff.
 
ElectricFreak said:
Hey,
the machine only has 1 hopper.
a major problem is the super low density of this product makes it incredibly difficult to measure hopper level, with any reliability.
It would be much easier to measure the level of a hopper full of styrofoam peanuts, than this stuff.
Click to expand...

That is why I would do weight

Dan Bentler
 
We have tried to meter the product out by a loss in weight hopper. (designed by someone before I got here)
not only does this slow the process down tremendously, it is very difficult to do when the product is delivered by air. If the air pressure on the product delivery varies .01 psi, this is multiplied by the square area of the hopper capturing the product. Thus any little variation of pressure makes the weight values useless.

Idealy I would like to do a loss in weight setup. I think I could design one that would work. But that would require a basic rebuilt of the entire production facility. I cannot pull that off at this time.
 
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Hi PhilipD,
I agree it is sort of a rate meter.
You got it exactly correct.
"This meter would display the total weight bagged in the last five minutes and would be updated every second"

It dosen't have to be updated every second, but that would be ideal.
I can already keep track of the weights, by using multiple copy commands. every output cycle bumps the weights down 1 address.

I need a way to tie a "timestamp" value to the weights, so that I can delete them according to their age.

Thanks,
Chris
 
I am considering copying the time to an address in parallel with the weight copy.
Right now every bag weight is copied to F60:0, and bumped 1 address with each new bag output.
So if I wanted to do the same with the time -in a parallel copy command, what format should I use?

I know the time is a status value now. but what type of value and how to format it so that I can calculate the last XX minutes from it?


Chris
 

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