Slightly OT: Pneumatic actuator for position probing

Ken Roach

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Apr 2002
Location
Seattle, WA
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Does anyone make a "positioning cylinder" like the Festo DDPC but with a digital encoder feedback ?

I have an application where a 0.0005 mm pencil probe is overkill, but a 0.1 mm analog cylinder feedback is insufficient.

I'd like to be able to get 0.001 inch accuracy out of the cylinder, with an interface over SSI, IOLink, or EtherNet/IP.

The application will be an oppositional probe arrangement for measuring material thickness. I think I want a "servo pneumatic" system because I need to move relatively quickly through several inches (past a holding frame) and then slow down and reduce pressure right before I touch the part.

Festo is our usual brand for pneumatics, but we're open to SMC and anything that can be bought Stateside and connected to ControlLogix.
 
Leatherman uses our controller to bend metal parts for it multitool.


The problem is the quality of the air. Dirty air gums up the cylinders.
High friction cylinders with high about of static friction to dynamic friction are also a problem.


However, the pneumatic control can be achieved.



https://deltamotion.com/peter/Videos/PneuMove2.mp4


Force control or position/force limiting can also be achieved.


This is probably overkill too.
 
Thanks, Peter !

There will be an RMC on another part of this system controlling eight hefty hydraulic cylinders. I think I'll need the RMC200 because I want to control both force and position on all eight, so I need 16 control loops.

The position probes are functionally separate enough (and may have their own cabinet) that I will consider an RMC70 for that feature. I didn't know it would work like that with pneumatics.

That looks like an R-series Temposonics, so we can get the position out of the RMC75E CPU itself. What sort of accuracy could we get from one of those sensors ?

I'm not a hydraulic motion expert by any means, but I've built (or fixed) enough "poor man's positioners" to make a decent budget argument to buy a proper controller.

Time to walk the dog and get some rest.
 
Instead of using probes that touch the material, could you use an optical non-touching sensor ?
It would be much simpler as compared to a pneumatic arrangement of opposing probes.

This one has an impressive resolution:
https://www.sick.com/dk/en/distance...ment-sensors/ol1/ol1s-ol1e-r1010a13/p/p579345

Measuring range 10 mm
Installation distance 0 mm ... 300 mm, Sender/receiver
Minimum detectable object 0.2 mm
Repeatability 10 µm
Linearity ± 40 µm
Response time ≥ 0.5 ms
 

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