Sensor for measuring web thickness?

Hello All! I know this may not be quite an appropriate question for this site, but.... I am looking fo a non-contact sensor to measure the thickness of a Web as it is fed into a machine. The material is a filter type media composed of basically paper fiber. The problem I am trying to solve is that the supplier of the paper is prone to "splice " the roll during production, and this causes us tremendous problems when we try to process it . The splice is almost always overlapped and then taped. This causes my process to jam severly, resulting in about 20 minutes of downtime on each occurance. If I can detect the splice, and stop the machine, restarting takes about 1 minute. Until QC can resolve the problem with the vendor, I want to install some sensors to detect the thickness difference. The range is about 1mm for a correct piece, anything more than 1.5mm should be detectable. Anyone with first hand experience with this kind of sensor?
I have looked at most of the sensor sites that I usually use, and none struck me as a good match.


All comments greatly appreciated!!!!

Thanks

A relatively inexpensive option might be to use something like a Keyance laser, looking at the web going over a constant angle idler roll (load cell roll would be ideal if properly designed)...

Either use the analog output to tell of a large delta, or get one that can be programmed to give a go/no-go digital output.

I only suggest Keyance as a brand name, as I know they can do this, but others (Banner, uhhh... well, others) probably can as well.

Costs should be in the $1500 to $2500 range.

---- EDIT ----

If you are dealing with material from a supplier, and are on good terms with them, then perhaps an even cheaper solution would be for them to use a specific color for their splice-tapes. In that case, a color sensor would be cheaper, and give a nice on/off output.

Banner would work for that (again, as others).

Along the lines of detecting the spice tape, I had excellent luck using a Sick KT 3W-P1116 contrast sensor (US$170.00 list) to detect splices in foil-backed cap lining material.





-Eric

The question is appropriate for this forum, especially if we learn something in the process!
I started the Google search with 'paper thickness detector'. I suspected ultrasonic was the way to go. This link shows what should happen when 2 webbed sheets are overlapped:

http://www.bbhscanners.com/products/spectrum_xf/UMD.html

Next, I searched for 'ultrasonic thickness sensor'.
The line from Sick looks like a perfect match. Your application is mentioned on page 2:

http://www.sick.com/us/products/new...le.tmp/Ultrasonic Sensors Family Overview.pdf

Thanks All!! I am checking these options.

Thanks Again.

I used to use a Synatel splice detector (uses capacitance) a while back. Used for rejecting splices on sheeters.

I assume you are running at high speeds. With a splice detector, sensing the splice with a sensor is one thing. You can't forget about the device to read the high speed signal. I used a sick sensor and a siemens logo plc(programmable relay) on a splice detector a few months ago. Are top speed is 750 FPM.

PLCRookie,

I just had a demo on a camera system made by Banner check here, this is one of their models, $1,300.00 I think it may work for you as well, we are getting 2of check back with me in a month or so, if you are still looking for one and I will give you the review

Thanks Genius. I think Im going to use a ultra sonic for this app.. but we just got a small machine built locally with this Banner unit, and it looks like we will get more in the future. Thanks ALL!

Try NDC Infra-Red Engineering - they specialize in this application .