detecting EPP(expanded polypropylene)

Hi,

I need to detect if an EPP piece is inserted in a mould or not before the other product is injected..
Wich sensor can I use so I can use the signal to send a triggersignal to the PLC? I was told that a capacitive sensor does not detect EPP.(Haven't had the change to try though) Anyone with experience about this problem?
Thanks

Why can't it? A capacitive sensor or a photoelectric can sense any material that fills a designated space at a designated distance.

http://www.sick.com/gus/products/product_catalogs/industrial_sensors/capacitiveproximity/en.html

From what I've been able to find polypropylene has a realtively low dielectric constant. EPP, which is largely air, probably has an even lower dielectric constant. I haven't been able to find an actual number on that. So I would guess that capacitive sensors simply can't differentiate between air and EPP.

However, I would think a convergent beam photoeye would be able to detect this, especially one of the hi-perf fiber optic laser ones.

Keith

Detecting plastic parts.

We have run into this type of application quite often. One of our customers uses a camera system. When the mold opens, there is a slight delay before the camera takes a snapshot, and then if all parts have been ejected the camera gives the press an OK to close signal for the next part. This can be set up by interfacing the camera inputs and outputs with time delay relays, or a PLC.
This customer is producing parts which require very stringent specifications. I personally thought the camera option was a little expensive, but then they told me the replacement cost of the mold. I am not sure of your application, but this maybe something you want to consider.

Big Al.

Al,
do you happen to know the brand of camera he was using? Does anyone have experience with such camera's? I don't know if there are camera's that can cover areas as large as 1,5 meter at 0,5 meter. The inserts used aren't that small so it should be easy to see the difference between an insert or no insert.

Camera Types.

This particular customer likes Keyence Cameras, with a CV2100 Controller, and a CA- DC100 illumination controller. I have also seen DVT and Cognex used for this application. My recommendation would be, to contact a local representative, and have them bring a camera in and look at your application. If your parts are pretty large, you may be able to use a simple vision sensor. I believe that IFM Efector now has some vision sensors that may work.

Big Al.