Reader Feedback: Hydraulics Questions, Distributed I/O Works and Sustainability Is No Hoax

Readers' Respond to Our Article "Green Technology Hoax," "Out of the Cabinet" and "Can A PLC Handle Hydraulics?" Read What They Have to Say

Stop Whining, Do Something

When I first read Dan Hebert’s article [“Don’t Fall for Green Technology Hoax”] I was expecting to engage in something more. However, it’s about the same things I’ve read elesewhere on this subject.

Neither Hebert nor I can do much about porker politicians and the U.S. citizens who continually put them into power. So suck up and digest the subsidies or take action. Don’t whine.

Neither Hebert nor I can do much about porker consumers of energy. So suck up out-of-control consumption or take decisive action. Don’t whine.

We can’t discuss alternatives on the “grand scale” and then say that we bought a (a=1) refrigerator and washer/dryer. Did Hebert buy one for everyone in California? Are we talking one wind generator or 100 million of them?

General Motors isn’t going to build a 60 mpg machine. The U.S. population isn’t going to use less energy given its thirst for fuel-guzzling transportation, and we certainly can assess that the U.S. isn’t going to do anything politically incorrect. The Department of Transportation hasn’t engineered the system or created the atmosphere for a highly efficient and effective transportation machine.

“Can’t wait for retirement. My job is to wait for retirement, so that I can buy a RV and gas my way across country.” This is today’s mentality in the U.S.

Bio fuels, solar, wind, thermal mass, moon gravitational pulls and the like are nothing new. Yet today, here in coastal North Carolina, there is barely a sign of mass consumer participation in harnessing them, or in energy-efficient thinking (college-educated rich kids?). Has anyone taken the initiative to learn why?

The human machine is no more than 14% efficient. Should we abandon or write off this model and machine better?

Well, I better go check the readings on my solar panels. They’re silently working, no matter how inefficient (about 14%) they might be.

Yes, there is a lot of fake green out here. I’m actually doing something about that. Are you? Are we ready for the challenge?

Vladimir Toman, founder, Lorin Technologies

Distributed I/O Works

Regarding your article on machine-mount, IP67-rated I/O components [“Out of the Cabinet, on the Job,”] we changed our manufacturing philosophy about four years go, changing from discrete, hand-wired relay logic to full PLC control with distributed IP67 I/O. The physical control box decreased in size by 80% due to the removal of relays/terminal blocks and the multitude of cord grip holes punched in the box to accommodate each individual I/O. Removal of all the drilled holes also decreased build time and improved IP rating. Labor to build the control box decreased 80%. They now build the control box in a day, as opposed to one week.

Assembly defects were cut dramatically and nearly eliminated because the hand-wiring of each circuit became obsolete. This led to improved turnaround times in manufacturing. Since the I/O blocks led to distributed control, the machine can now be modularized. Each section can be tested individually and isn’t as reliant on the main control box. Only power and communication are required instead of 25 I/Os and power.

Cable costs were dramatically decreased due to switching from multi-conductor I/O to communication/power  cable. Vision of the machine also was improved since some I/O were obstructed from view or hard to physically observe. Since the I/O blocks had LEDs, you could use them to determine the state of the I/O. There’s also an improvement in safety since an operator can view the status of LEDs remotely, away from the moving parts.

Bills of material became more manageable. Instead of needing cable, connectors, cord grip, as examples, for each I/O, it’s now handled by one cordset. Since all cordsets are fully over-molded, the IP rating from the sensor to I/O block to the PLC remains at IP67. When wiring by hand, you lose this rating since hand-wired solutions don’t maintain that level of protection.

Approximately 200 lb are removed due to the changes. On the older system, assemblers used a forklift to install the control box. Now you can hold the control box in your hands.

Inventory was more manageable—the logic was now in the PLC or I/O, not in the relay logic. This meant you could build a generic control box for every machine. Remote I/O provides upgrades and prewired solutions. The amount of I/O was selected to make machines generic, so options were installed easily.

Since the I/O blocks offer additional I/O, an upgrade was more plug-and-play than having to drill new holes in boxes, add additional relays or terminal blocks and hand-wire.

Name Withheld by request, electrical engineer, material handling equipment manufacturer

Better Than Slam-Bam

The hydraulics question [“Can a PLC Handle Hydraulics?”] presumes conventional slam-bam hydraulics. For a new design, the time is right to consider a pump-modeling hydraulic drive. Sort of a marriage between electric servo control and hydraulic power, these systems have excellent control capability. They also can be smaller than conventional hydraulics. Peak power is required only to accelerate and decelerate the load, but, since steady motion requires less power and idle time requires no power, these systems can take advantage of peak and RMS ratings of smaller-sized equipment. Conventional systems typically operate at peak levels all the time, wasting energy and heating oil during much of the machine cycle.

JIM BALDAUF,
UNiGY applications engineer,
Kadant AES

Built for Hydraulics

Some standard PLC manufacturers have control modules specifically designed for hydraulic cylinder control. Using analog I/O modules with appropriate feedback devices and proportional or servo valves can provide good results as well.

Bob Strasser, plant engineer,
Triumph Fabrications

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