Interesting project tracking web weight

Hey guys, I have an application in which I need to track web weight for a certain distance, then add it to an accumulator. I've never done an application like this before. My thoughts were to divide the web into sections of 1 foot, then assign each foot of material a density. As the material reaches a certain point, I would add mass to an accumulater at a rate based on the density of the material in the selected 1 foot interval and the line speed. This seems like the simple way to do it. I'm just wondering what other options are out there, and if any are recommended or, if this method above should be steered away from for any particular reason. Thanks in advance.

Russ

I can't believe it

I can't believe that no one has any input to weigh in on the best way to do this, or landmines to look out for.

Well, personally, I have no idea what a "web" is or how you would measure it's density (Im assuming it's variable?) You have also left out any hardware you might be using.

Yes, I have read this thread many times and all that comes to mind is the web of an I beam or something like that. What are you working with?

Are you trying to measure potato chips going into a seasoner? Or some product that is feeding another process? Like coffee beans from a hopper to a grinder.


For starters, you could measure the NO LOAD amps of the empty web, then the FULLY LOADED web amps then 1/2 of full load. You could then use the differences of the loading to determine weights.

I don't quite understand what you're measuring or what you're trying to do with the measurement.

Are you measuring weight, density, or length?

By web, are you taling about a roll or strip of a flexible material?

How are you going to measure the density again?

How did you plan to measure the weight of a section at a time if it is all connected?

Why not measure the length and the accumulated weight as it is wound up or otherwise stored at the end of the process?

Give us more help understanding what you are actually doing and your responses will grow in quality and quantity...

We have a commercially available weigh belt feeder here. It has two load cells under the belt, the first one, before the product drop chute is the 'tare' load cell, the second, after the drop chute measures the belt loading in lbs/ft.

The speed of the belt is accurately controlled, and the belt loading (lbs/ft) is integrated over the rate to determine current throughput in lbs/hr. Is that something like you are talking about?

Are you talking printed or unprinted web? Are you trying to find out ink thickness.

PLC gurus make great comedians.

I get it. I'll be a lot more specific. The following information is not really related to the question, but may allow for a better understanding of the question. Web(material) is unrolled off an unwind stand and is conveyed a certain distance to a winder. The material is wound around a core with a specific density in mind. Currently, pack pressure is varied to obtain the desired density, but this method is inefficient due to variations in web density, and other factors. So, the goal is to calculate the correct desired density throughout the winding process, and adjust parameters accordingly. Initial testing of this method yielded positive results, but we can further improve the process by adding the mass to the "bun" as it actually becomes part of the bun, rather than setting an average value for certain material and "hoping" that the density throughout the length of the "jumbo"(unwind) roll is consistent.

Now, the question. We have a scale that reads unwind jumbo weight. Somehow, as material is rolled of the unwind stand, I need to determine the mass of the web, then track this mass X distance(not defined yet), and apply it to the winder. The unwind scale reads 0-6000lbs. My question is in the methodology of tracking the mass of the web. My thoughts were to divide the web into intervals of 1 foot. Assign a density(mass per linear inch) to each 1 foot section of the web, and add it to the winder value as it reaches the desired position. This would be a simple way to do it. However, I'm questioning whether it's the BEST way. This is where I'd hoped some of you would weigh in.

All responses welcome. Even if it's no real help to the problem, I do appreciate a good laugh.

Russ

http://www.strandberg.com/density/
Just an idea........

Thanks, but....

Thanks for the info Bob. Given a new application, I'd look at this, but the hardware capital $$ for this for hardware is nil. This must be accomplished using hardware in place. This hardware in place basically is the scale reading the jumbo(Unwind) weight.

NOTE: The calculation of density, mass etc is not the question. The question is the BEST way to track this density from one position to another.

P.S. I just read one of the responses again from above. FYI, the web is unprinted.

Russ this might help?
http://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.html

rdrast said:

The speed of the belt is accurately controlled, and the belt loading (lbs/ft) is integrated over the rate to determine current throughput in lbs/hr. Is that something like you are talking about?

Click to expand...

Yes, this is pretty much exactly what I need, but I do not have $$ for hardware. It must be done with existing hardware. It's possible, though probably not as accurate as the equipment you described, unless there is a better way to do this that I am not aware of. Hence my question.

Do you have any kind of feedback as to how far it has traveled? How are you going to know when the 1 foot section reaches it's destination?

Without any kind of sensors or limit switches or anything else the only thing I can think of is motor RPM. Assuming that is constant of course, or capable of being monitored. Then you could calculate how far a section has traveled in a given frame of time.