sheet edge detectors

I need recommendations for a sheet edge sensor for roofing manufacturer. We are currently using 2 contrast sensing photo eyes and because of sand, slate fumes and steam we need to find a more reliable solution. the fiberglass sheet is just exiting the asphalt coater so it is quite hot (350F) and I want to go to a thermal sensor as it would not see the dirt as readily. Does anyone have any experience sensing sheet edge this way? I will be against a water cooled drum and the output will be controlling 3 Yaskawa servos that can be programmed for either digital or analog control.

thanks...Larry

Fife has a lot of experience in web guiding systems. They might have a sensor for high temperature, dirty environments like yours.

I dont have experience with that but I saw someone who used Ultra Sonic sensor Reciver&Transmiter.for edge control.
Just idea.

I don't have any experience her either, but what about a SICK laser?

Am I missing something here?

Surely the simplest (and cheapest) solution would be a long range through-beam photo switch!

Anthony

we currently are using laser photo eyes, we have tried color and contrast sensing...but the major problems are with them getting to dirty within an hour or the dirt and sand on the drum causing false readings. we have fife guides elsewhere on the line and they work great but in this spot anything close to the product is gonna get trashed. what i am considering is an infrared scanner placed 2 to 4 feet away...thermal contrast between the sheet and the drum should be more than adequate, however the scanners we used in the steel industry were good only down to 450F and i dont know what else is available

larry

unfortunatly thru beams wont work in this location, the sensor has to be mounted to the moving stand and thus we are restricted to the sheet against the drum. we also have air purge systems installed but that has just been fogging our lenses

Hi ldavis7999,

Try these people DELTA-USA , or American Sensors Corporation . The latter Im using right now to control the position of a looping pit, via hot to cold transiton sensing. Might work for your application.

Good Luck

Andrew

Larry,

please state how accurate, and how fast the edge detection must work.

Do you need an analog value for where the edge is, or is it sufficient with a fixed ON/OFF point.