Typically we use Parker cyliders with linear feedback built in. The cylinders utilize a rolling pot.
This allows us to read the cylinder position in the P.L.C.
I have done this one way and know of another way which may be possible.
I had a press which shuttled a die set back and forth and needed to know linear position. I used a LVTD connected to the rod end of the cylinder. Most LVTD manufactures have different classes of products ment for different industries. My app. was very dirty, and a lot of vibration. It worked pretty well. Used a sperical rod end coupler at the end of the LVDT for any mis alignment.
Hydroline (Rockford Ill.) offers as a option a internal LVTD which is inside the barrel of the cylinder. Got to think about cost, maintenance, etc. Suitible for most PLC applications.
You could look at changing the ram to suit an LDT, I have used these on sawmilling equipment with both Temposonic and Balluf transducers. The transducer is fitted into the centre of the ram with the rod having a hollow centre. A magnet is fitted to the piston end and is quite reliable and robust.
Look for Temposonic transducers which will readout linear position. They are very durable, accurate and interface to a PLC easily. look for them on the web at "http://www.levelplus.com/":http://www.levelplus.com/ .
Check out the Balluff magnetostrictive units. Their BTL's are often used for this application. Length to 14' .
Gene Wilkins
CALL Associates. www.callassociates.net
LVDT's might be the best bet. Mechanical issues tho with mounting Resolution might be an issue to.
Have used encoders but depends on the mechanics again
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Jeremy Pollard, CET [email protected]
On The Web - http://www.tsuonline.com
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If this is a new application, then there are hydraulic cylinders which have linear transducers integrated into them. I haven't used any, so I can't recommend one, but I have seen them in brochures for hydraulic omponents. Try the major hydraulic manufacturers for these.
If this is a retrofit to an existing application or design, then magnetostriction devices are sometimes used for this application. These would be mounted externally to the cylinder. "Temposonic" is one well know brand
name, but there are others as well.
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Michael Griffin
London, Ont. Canada
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