I never learned about pneumatic devices in college, and I never used them in any type of equipment. But they offer interesting alternatives to hydraulic and electronic devices. In sensitive equipment, the use of clean air eliminates problems from a hydraulic-fluid leak, or a short circuit from a broken wire or faulty connection. Air comes in an endless supply, and it seems fairly simple to route it to just about anywhere we need it. If oxygen could create a problem, pneumatic equipment could use an inert gas.
I have seen rotary and linear-slide positioners and two-jaw pneumatic grippers in pick-and-place equipment used to assemble electronic and electromechanical equipment. Pneumatic devices require maintenance, but they don't burn out. They don't dissipate energy (except from a bit of friction). Pressure regulators and fittings are off-the-shelf items, and designers don't face RFI or EMI issues with air lines. Granted, a pneumatic system requires a compressor or source of pressurized gas, valves (probably electric), and some sort of electronic controller.
Where can engineers learn about pneumatic controls and devices? I looked at the undergraduate course offerings at three engineering universities and found nothing that relates to pneumatics except for courses on the theory of compressible fluids. So it might seem like it's anyone's guess where engineers pick up the knowledge to apply pneumatics.
The National Fluid Power Association Website includes a section titled, "What is pneumatics?" It includes information about pneumatics applications, fundamentals, training, and resources. A link on this page goes to a list of companies that offer training and additional information.
The International Fluid Power Society provides an extensive list of books and certification materials. It also certifies fluid-power technicians and engineers at several levels.
Parker-Hannifin Co. has an extensive training program. Look under "Technology Training."
Matrix Multimedia, a company in the UK, will soon have a pneumatics trainer and educational materials with the brand name Airways. This product line comprises about 100 rugged pneumatic components that mount on a stable aluminum platform. Each component has a label with the corresponding industry-standard pneumatic or electrical symbol. Students take the rugged components, mount them to the platform using plastic "t" bolts, and connect the components with nylon tubing to build working pneumatic circuits. They then use the curriculum provided to carry out experiments in pneumatic and electronic control. Sounds like a cool way to start.
A lot of us would like to learn what you have learned. Is there a way to break into the pneumatics gig? I would like to be able to counsel your engineers in the ways of the wind.
Unfortunately, for me it was baptism by fire, the school of bumps and hard knocks, etc. My normal role was the controls programmer, trying to get things to work, which forced me to learn.
If there are vendors in your area that sell pneumatic components, I would contact them. They usually have demo equipment, and might put on training sessions. I think you really have to get your hands on the hardware to get a feel for things. It is especially interesting to create situations where the actuators are undersized for the load. You can really see the effect of air as a compressible fluid.
I wouldn't use pneumatic devices for precise positioning, but for devices such as actuators and grabbers they seem to work well. If you have a positioner that moves from one limit to another, pneumatics might do the job quite well.
An advantage of air being compressible is that provided you use sensible size actuators that give enough force to work but are not over-sized, accidental collisions or foul-ups need not cause serious damage. I'm not recommending frequent foul-ups but they'll happen sooner or later if an operator loads something incorrectly or a work-piece falls out of a gripper. Foul-ups with hydraulics usually end in tears before bed-time. I have also seen buckled lead-screws from even quite modest servo positioners where torque limits haven't been set correctly.
Al, what's the best positioning resolution a servopneumatics system can get these days? You mention that servopneumatics isn't being used in high-precision applications. Is that because they can't get the resolution or is it because the resolution is too costly?
Chuck, During the interviews for an article I did on servopneumatics last year, the parameters they used to describe the applications for the technology is where high precision and positioning accuracy (<0.2 mm) is NOT required. Not sure how they would answer the resolution question. They also identified a good application fit for servopneumatic axes when there is a need to move large loads continuously (24/7 or high duty cycle operation), positioning systems operating on a low voltage, or solutions with space constraints requiring high feed forces and high dynamics. Hope that helps.
Chuck, Forgot the second part of your question. I don't think pneumatics is too costly. The precision limits are a reflection of the underlying technology, especially when compared to electromechanical solutions which can achieve very high precision, resolution and repeatable accuracy.
Pneumatics is becoming an important component in the field of Mechatronics for efficiency and motion control precision. Festo is a leader in pneumatic based robotics with their gripper and arm products. I remember taking a Pneumatics class at community college back in the early 80s. I didn't see the importance of this class because of my fascination with electronics. I which more emphasis on system integration was discussed in class as it relates to Mechatronics, maybe I would have considered working for engineering companies like Festo who makes great and cool pneumatics based robots instead of just electronic/semiconductor jobs.
The last pneumatic positioner I worked on was in a vertical orientation, which created additional challenges for the actuator. The systems I have worked on used "magnetostrictive" position feedback ("Temposonics" would be one trade name). This feedback system is based upon timing pulses transmitted down a rod that get reflected back by a magnetic ring, or something like that. The time is converted to an analog output of some resolution. The resolution doesn't change as the length of the transducer gets longer, so the system resolution is typically affected by the transducer length.
The controls on this system were essentially analog in nature, comparing setpoints to the transducer position, and throttling air valves to try to keep the actuator in the correct position, and move it to new positions, etc.
The end result was less than what I would have desired (Fortunately I didn't pick the equipment, I was just called on to get it to work.). There was a tendency to overshoot significantly (large fractions of inches at least), especially when moving down. I don't know what the final position tolerance was, but it was not comparable to an electric servo actuator. It is also relatively noisy, due to the air valves constantly fighting with each other to try to position the load. I couldn't help but think that there would soon be a mechanical failure in the valves because of the frequency of the switching, etc.
Having worked with literally hundreds of servo systems of many different flavors, and a small number of pneumatic positioners (less than 10 probably), I would favor an electric solution unless there is some overwhelming reason to not use electric (explosive environment?).
Under ideal circumstances pneumatic positioners talk about 0.005" positioning resolution. That might be achievable under some circumstances, but if I were designing the system, I would be thinking a quarter of an inch and designing in energy absorbers and positive stops at the desired stopping points.
As a general substitution for this type of actuator, I would favor the belt drive style slides offered by a number of vendors. They offer high speed capability in a similar form factor, and the precision of a completely digitally controlled electric servo system.
Thanks, Al. One more question for you: Do you have any idea what percentage of oneumatics systems today are servo? I would imagine the percentage is very small.
The Machinist Calc Pro computes speeds and feed rates for milling, turning, and drilling: cutting speed, spindle speed, feed rate (inches/minute), cutting feed, etc.
During a recent meeting with engineering-school faculty and alumni, Contributing Technical Editor Jon Titus talked about whether colleges should educate generalists or specialists. What do you think?
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 3
Early in my career, I worked as a draftsman and remember the days of drawing on vellum with numbered pencils and Mylar with plastic lead. This was a fun experience in the sense that I ...
I've been using workstations for more than 10 years and love finding ways to get more performance from my system. With demanding professional applications that require more power each ...
A lasting memory from my first job as an engineer in an auto assembly plant is standing on hard concrete at six in the morning, vending-machine coffee clutched in hand, listening to ...
A quick look into the merger of two powerhouse 3D printing OEMs and the new leader in rapid prototyping solutions, Stratasys. The industrial revolution is now led by 3D printing and engineers are given the opportunity to fully maximize their design capabilities, reduce their time-to-market and functionally test prototypes cheaper, faster and easier. Bruce Bradshaw, Director of Marketing in North America, will explore the large product offering and variety of materials that will help CAD designers articulate their product design with actual, physical prototypes. This broadcast will dive deep into technical information including application specific stories from real world customers and their experiences with 3D printing. 3D Printing is
To save this item to your list of favorite Design News content so you can find it later in your Profile page, click the "Save It" button next to the item.
If you found this interesting or useful, please use the links to the services below to share it with other readers. You will need a free account with each service to share an item via that service.
Tweet This
2 
