Wednesday, August 22, 2012

Measuring belt speed

Many vision systems inspect objects, often bottles, moving along on a conveyor. Usually, when a nonconforming item is seen a signal is sent to a blowoff device or flipper that sends the offender to a scrap hopper. Clearly, this entails keeping track of where the object is, which means counting encoder pulses.

If your conveyor has an encoder, all well and good, but many don’t. If that’s the case you’ll want to fit a wheel encoder. I’m sure there are many available but I did like the sound of the new MA20 measuring wheel encoder from Baumer.

This has selectable resolution all the way up to 25,000 pulses per rev, and its large diameter, (larger than any such wheel I’ve seen,) should ensure good contact with the belt.

You probably have your favorite such products, but I thought I’d throw this out.

One aside: I consider it good practice to accept the good rather than reject the bad. By that I mean I like to use a diverter to send the good product where I want, letting “bad” be the default condition.

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