light curtain to keep fabric centered

irondesk40 · Jul 23, 2013

Here i go again. Another question. Has anyone had success with controlling the position of fabric being fed by feed rollers with the use of a light curtain. In the past what i did was i had two break beam type photocells mounted just off the edge of the fabric on both sides and if either of those detected the fabric then i turned on a motor to move the feed rollers in the direction it needed to go in order to keep the fabric centered. We now looking at having to use a light curtain that will be large enough to keep a piece of fabric 40 inches wide centered as it is being fed through a machine. I would assume the light curtain would give a analog signal out. New to me. Anyone ever done this?

JordanCClark · Jul 23, 2013

Nope, but I'm assuming you mean an array sensor rather like like this one:

Banner A-Gage EZ-Array

These particular ones would come with two analog outputs. One of the measurement modes gives the midway point of a blocked section. That would be used as your process variable.

Depending on which manufacturer/unit you choose, your mileage may vary. Any data on what they want to use?

maxketcham · Jul 23, 2013

some of the things you will want to think about with light curtain sensors, is the opacity of your material, the dust/ dirt in the air around the sensor, and the possibility of dirt building up on the sensor head.

make sure you know all the above because any one or a combination of them, will cause a offset to center you will have to deal with either built into the sensor, or in software.

kvogel · Jul 23, 2013

Balluff has a nice line of light grid sensors as well

http://www.balluff.com/balluff/MUS/en/products/Light-Grids.jsp

Analog inputs and a bit of math and you're on your way.

Ken

Mark Buskell · Jul 23, 2013

We use the banners a lot in the carpet industry. Banner also makes this clear plastic tube that the sensor sits inside. It keeps the fibers off the sensors.

JRW · Jul 23, 2013

Iron

I have these this (tilt roll that guides the fabric or keeps it straight)
But still only on the edge- not the complete width of the material

If the fabric is covering say 3/4 of the eye (band of eyes maybe 7 vdc) then the roll tilts to correct material to center of sensor

irondesk40 · Jul 24, 2013

thanks. I called banner yesterday and a rep is suppose to come in next week. i looked at the array sensor with what he referred to over the phone as middle beam block. From his description the banner is a 4-20ma output. From my understanding if the fabric is centered under the array then you would get a 12ma signal out. the way i understand it at this point then i could just connect the input into the micrologix plc which is what we use and read the value at 12ma and as if the value goes below or above the 12ma value then you can determine which direction the fabric is going on the belts and which direction to try to correct to. At the moment i am not sure what the mechanics will be to accomplish this. In the past i did this on a machine we purchased that had a motor that would shift the whole feed belt assemby left or right to keep the fabric centered. that machine only ran about 6 yards per minute and this machine will run about 15 yards per minute. Am i way out in left field on my understanding on how an array would work? Hopefully next week will have a better understanding.

iant · Jul 24, 2013

there are laser sensors aas well as vision system Camera's that can handle that .
Most of the 'light curtains' are not designed for yur tassk but the laser sensor or a camera can handle that with ease

mjggjm12 · Jul 24, 2013

We use Fife web guides. They can be set up for edge guide or for centering. They can also be set up on devicenet or most other industrial networks.

maxketcham · Jul 24, 2013

irondesk40 said:
thanks. I called banner yesterday and a rep is suppose to come in next week. i looked at the array sensor with what he referred to over the phone as middle beam block. From his description the banner is a 4-20ma output. From my understanding if the fabric is centered under the array then you would get a 12ma signal out. the way i understand it at this point then i could just connect the input into the micrologix plc which is what we use and read the value at 12ma and as if the value goes below or above the 12ma value then you can determine which direction the fabric is going on the belts and which direction to try to correct to. At the moment i am not sure what the mechanics will be to accomplish this. In the past i did this on a machine we purchased that had a motor that would shift the whole feed belt assemby left or right to keep the fabric centered. that machine only ran about 6 yards per minute and this machine will run about 15 yards per minute. Am i way out in left field on my understanding on how an array would work? Hopefully next week will have a better understanding.

with the web guides I have seen either you shift the unwinder l/r or you shift a set of rollers angularity after the unwind to cause the web to center. I'm not sure that just shifting a set of rollers left or right will do anything useful.

shooter · Jul 26, 2013

a cheap system works with two LDR sensors and a simple amplifier. Itis analog and just compares both signals.

irondesk40 · Aug 5, 2013

thanks for suggestions.
Banner rep came in and had a ez array demo. Boss is dead set on using that. Not exactly sure how the mechanics will be done yet.

iant · Aug 5, 2013

Always the rep. Sometimes good
Although banner and keyance both have specialty sending devices

light curtain to keep fabric centered

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