OEM's Head-to-head Pneumatic vs. Servo Test Shows CPGs Savings

Stacking equipment manufacturer Forpak devised a test to see how incumbent pneumatic actuators stacked up against newer mechatronic servo technology, specifically on a frozen food stacking and laning application. These are the results.

Dave Brownson, Engineering Manager at Forpak, was the first engineer hired onto the food stacking equipment OEM when it opened its doors more than 30 years ago. With three decades under his belt as an engineer with the company, Brownson remembers the days when pneumatics were the only actuator game in town for Forpak machinery applications. He also recalls the first introduction of linear servo in the place of incumbent pneumatic technology about six or seven years ago.

“I was looking for a IP69K solution for a project that we had, so I went to my vendors and they came up with [linear drive system supplier] LinMot,” he says. “I was introduced to them, and we’ve never looked back.”

More recently, Brownson has had his sights set on building an all-electric, pneumatic actuator-free stacker. But it was a matter of waiting for the right size and shape of linear motion tech to be ready—nothing existed on the market that could fit his application.

“I had kept on pushing Peter [Zafiro of LinMot] to make a smaller and smaller motor, and he asked me, ‘How many would you buy?’” Brownson recalls. “I answered, ‘Well, how many can you make?’ Because if I can make an all-electric stacker, it would really make efficiencies go up.”

Brownson finally saw the LinMot prototype that would do the job at a recent PACK EXPO. Forpak is now developing a machine that is 100% electric with no pneumatic technology. The plan is to exhibit the new machine at PACK EXPO International, to be held Oct. 23-26, 2022 in Chicago.

It bears mentioning that pneumatics aren’t going anywhere, and they are firmly ensconced in the controls and automation tool kit. And some operations require pneumatics for safety reasons, in explosive environments for instance, so switching out pneumatic for electric isn’t always possible.

Still, Brownson sought producing an all-electric model because he says LinMot linear servo motors save energy and are highly efficient for his specific set of applications and customer base. Plus, they allow for a lower total cost of ownership thanks to their comparatively few wear items, and that results in less downtime—especially unexpected downtime. In his experience, these factors bring real-world, long-term savings that are attractive to Forpak’s CPG and brand-owner customers.

But so far, that’s just been Brownson’s anecdotal experience—one man’s opinion. To test the efficiency and power savings, Zafiro enlisted Brownson, along with Joel Geisel and Adam Shank, both from Hamilton Automation, a LinMot Manufacturer Representative, and JB Korte of Van Meter Inc., a LinMot distributor. The OEM, automation supplier, and distributors together devised a test of Forpak’s machine using pneumatic actuators as compared to all-electic actuators. The idea was to establish actual power consumption and develop actual energy savings data, and what follows is what came of this testing.

Equipment being tested

Forpak stackers occupy a niche in baked product and protein packaging lines that exists between upstream freezers and downstream flow-wrapping, bagging, or hand-packaging. Typical products might be frozen hamburger patties, waffles, or cookies that exit the freezer either randomly or semi-organized. That product needs to be oriented, laned, and stacked for downstream packaging equipment.The above Forpak Stacker (Model Number – GSS5-8) is a typical electric vertical stacker with pneumatic horizontal cylinders used for stacking products. The Stacker can be manufactured in three to ten lanes depending on production demand. The test model was a four-lane unit (Model Number – GSS5-4). The picture also shows a takeaway conveyor attached for manual or downstream automated packaging.The above Forpak Stacker (Model Number – GSS5-8) is a typical electric vertical stacker with pneumatic horizontal cylinders used for stacking products. The Stacker can be manufactured in three to ten lanes depending on production demand. The test model was a four-lane unit (Model Number – GSS5-4). The picture also shows a takeaway conveyor attached for manual or downstream automated packaging.

“The slide plate and push parts of the stacking were pneumatic, and they always have been, up until just recently,” Brownson says. “Now that LinMot developed the right size actuator, we’re able to do both traditional pneumatic and all-electric, and we performed this test to see the difference.”

Forpak assisted by allowing the team access to a typical stacker machine in operation at many end-user sites. The stacker machine is a four-lane machine, with eight pneumatic actuators operating in a horizontal direction.

With the help of Korte from Van Meter Inc. and a Rockwell Automation Power Monitor 5000, actual power consumption was recorded. The Power Monitor traced data points including amperage, time, and kWh from an independent, high-efficiency 7 cfm electric air compressor. The team ran the machine for 30 minutes and sampled every 10 msec. This setup does not account for pneumatic line losses as the air provided to the cylinders had a very short run from the compressor, with no other devices operating on the same air supply.

Findings

The test team ran into one limitation during the test run—the number of data points able to be stored in the PLC. As such, the data pulled was for 15 minutes of run time, and the average power was consistent throughout the study. Running the machine for an additional 45 minutes to achieve an hourly count proved that the data would not have changed. The compressor never turned off in the entire 60 minutes. So, the team says it’s confident that the data pulled for the entire 60 minutes would have been nearly identical as the 15 minutes test data, extrapolated for the 60-minute  test. The power consumption was consistent at 5161 kWh throughout the test.


Test notes: Testing was completed on November 2nd 2021, at Forpak’s manufacturing facility. It was completed by Adam Shank of Hamilton Automation and JB Korte of Van Meter Inc., with the help of Dave Brownson of Forpak. Evaluation and analysis of results were completed by Joel Geisel of Hamilton Automation.


LinMot’s Lin Designer program shows this specific horizontal pusher application and provides for calculated power consumption for the LinMot actuators and an equivalent pneumatic cylinder. Lin Designer’s pneumatic cylinder power consumption calculations are based on the two most popular pneumatic cylinder manufacturers’ energy power consumption calculations. These are direct-from-the-factory expected energy consumption rates.

For this specific cycle, LinMot’s Lin Designer program estimates 4575 kWh power consumption. The test used the lower of the two values to calculate pneumatic cylinder energy operational cost, as follows:

The 4575 kWh multiplied by a fully loaded $0.20 per kWh (test note: this value is usually much higher, especially when plants run during peak surcharge periods during the daylight hours for most of the calendar year) would yield an expected cost of $915 per cylinder per 8,000 hours of operation per year. Since this machine uses eight pneumatic cylinders, the operating cost for this specific machine would be $7,320 per 8,000 hours of operation per year.

The equivalent machine using LinMot actuators provided linear motor yields the following power consumption result:

The same cycle resulted in 243 kWh for a PS01-23x80F-HP-SSCP-R20 motor in a 175 mm cycle in 200 msec and -175 mm in 200 msec with a 600 msec dwell time. The 243 kWh multiplied by a fully loaded $0.20 per kWh would equal $48.60 per LinMot actuator. All eight actuators would cost $388.80 to operate 8,000 hours of operation per year.

The savings here are calculated to be $7,320 (pneumatic) minus $388.80 (electric), or $6,931.20 per calendar year. If a plant operates at lower output, say to a 6,000 hours per year schedule, the savings would be $5198.40 per calendar year.

Zafiro, Geisel, and Korte note that these values do not include any maintenance or unexpected downtime costs when a pneumatic cylinder fails.

“Such fails are more common in with frequent cycling applications, such as the one in this study,” Brownson notes. “I’d estimate that replacing a pneumatic cylinder usually takes between 30 to 90 minutes, with typical plant downtime being valued at $15,000 to $20,000 per hour. Even though it’s not considered in this test, downtime is huge.”

“There are very few mechanical pieces with this type of actuator, so you essentially limit the amount of wear that could happen,” Geisel adds. “And by limiting the amount of wear, it requires less maintenance than what a pneumatic cylinder would require. You don't have seals that are breaking down. You're not losing air, and you're not having to replace cheaper components more often. There’s just very little wear or necessary downtime.”

Results

The test study revealed that, at least for this specific application, running eight pneumatic cylinders costs significantly more than eight linear motors. According to data* from the world’s two largest pneumatic cylinder manufacturers, the carbon emission savings would be over 4,600 lbs. per cylinder, or more than 36,000 lbs. of CO2 emission savings for this specific machine with the 8,000 hours per year operation. 

Adding this to the more than $6,900 worth of electricity cost savings, Brownson was impressed. He notes that this test was done on a four-lane Forpack stacker machine. A typical Forpak stacker uses between six and 10 lanes, meaning for those machines, the savings will be higher as extrapolated over more lanes.

“I was expecting a savings, but I wasn't expecting this amount of savings,” Brownson he says. “It really will help me in showcasing the new machine in the future—as far as at PACK EXPO International, and for sales in the future also. It shows that the cost of ownership on the front side is going to be a little bit higher, but overall, the course of the life of the machine, it'll be less.” PW

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