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Putting hydraulic machines on an energy diet

A guy walks into a molding shop with big machines and asks the plant manager, “Want to bet that you can cut machine energy cost 35%-55%, with payback in about a year, and have no negative effect on productivity?” This is not a joke.

Rob Neilley

January 20, 2010

8 Min Read
Putting hydraulic machines on an energy diet

A guy walks into a molding shop with big machines and asks the plant manager, “Want to bet that you can cut machine energy cost 35%-55%, with payback in about a year, and have no negative effect on productivity?” This is not a joke.

One reason for the continuing proliferation of all-electric injection machines is their energy efficiency—using as little as 40%-50% of the energy needed by comparable hydraulic machines. Some recently introduced hybrid machines can provide nearly as much energy savings, while technologies such as variable-displacement pumps can also reduce power bills.

As industry consultant Robin Kent points out in his article on p. 4 of our special energy supplement to the January issue, energy savings is about the hottest topic there is these days. It moves money from the expense column to bottom-line profit, and as a bonus, makes the company greener. However, even though electric and hybrid machines are excellent solutions, what can be done about existing hydraulic machines—the ones running in your plant right now? They’re running well and making good parts. Sure, compared with newer electrics and hybrids, they are energy hogs, but they have one feature no new machine can match: They’re already bought.

Retrofit machine energy bills

A SyncroSpeed drive motor speed control system, which can cut hydraulic molding machine energy use by 35%-55%, is custom-installed on a press and occupies little floor space. A combination of hardware and software that interfaces with the molding machine control, a SyncroSpeed motor control is transparent to operators and near zero maintenance once installed. A simple touch-screen interface tells a user how much energy is being saved at a glance, and any changes in consumption can be maintenance alerts.

There are a variety of technologies and devices on the market to reduce energy consumption of molding machines, in addition to new presses themselves, and one that, after gaining a following in Europe and Asia, has begun finding believers in North America, too. SyncroSpeed comes from CCS Technology (Coventry, England), a diversified designer and producer of machine control systems. Its emergence in North America follows the recent assumption of North American sales and support by Plastic Metal USA (New York, NY), headed up by Robert Knaster.

One major difference from most other devices on the market is that SyncroSpeed was developed for injection machines, though it subsequently found additional applications. Knaster calls it the single biggest energy saver a molding company can embrace for improving energy efficiency, reducing energy costs and emissions, and improving its green status. He has documented experience to support that claim. The technology already has logged more than 2 million hours of production molding.

Match speed to need
SyncroSpeed is a hardware-software combination whose heart is an inverter-drive-motor speed control that can improve the energy efficiency of a hydraulic machine to nearly that of an all-electric. The software interfaces with the molding machine’s control system and directs the speed control hardware to keep the host machine pumps running at the best speed for maximum energy savings, while still maintaining full productivity.

It completely avoids the waste of energy when a pump runs constantly at full speed, even though the molding machine needs far less energy during much of the cycle, most obviously during idling. SyncroSpeed ensures that the precise amount of energy generated is what the machine requires at every point in its cycle—not a kW more or less.

Savings without penalty
The usual range of electrical power reduction seen in a molding machine with SyncroSpeed installed is 35%-55%. Naturally, that depends on the particular machine and operating conditions. Equally important, as SyncroSpeed’s Knaster emphasizes, is that this energy reduction has no impact on part quality and productivity rates. Cycle times remain the same.

Since the integrity of the machine is maintained, the presence of SyncroSpeed is transparent. Machine setters and other technicians work on the machine exactly as they did before SyncroSpeed was installed. After the supplier installs the device and tests it, there are no further adjustments needed and no maintenance beyond routine cleaning of intake filters for the inverter and enclosure.

Which machines can benefit?
SyncroSpeed technology can retrofit to most any injection machine and have a positive effect. Brands with SyncroSpeed already installed include Engel, Demag, Negri Bossi, HPM, Windsor, KraussMaffei, Stork, Mitsubishi, LG, Buhler, Sandretto, and Cincinnati Milacron. The system is interfacing with a variety of machine controls, from older relay types to more recent closed loop, proportional technology.

Savings are greater on larger machines—300 tons and up—with fixed-displacement pumps, without accumulators, having motors of 37 kW (50 hp) or larger, and a cycle of about 30 seconds or longer. However, even these are not absolute limits. Smaller machines, and larger ones with variable-displacement pumps and/or accumulators, are evaluated individually for optimum savings. For example, a machine that spends much of its production cycle idling can benefit (see  “An exception to the VDP exception,” below).

Typical results convincing
Supplier/client confidentiality agreements keep us from naming specific companies, though Knaster will provide documentation and references. But a few examples make the point. One 36-machine molding shop reduced its power consumption by 5.8 million kWh per year with SyncroSpeed, saving about $9.3 million over the first five years. Another molding shop, this one with six IMs, saved 2 million kWh per year with SyncroSpeed, which over five years let it keep about $1.2 million. Also, both companies wanted to reduce their carbon footprints. The first company’s five-year carbon reduction was 12,500 metric tons of CO2; the second company reduced its footprint by 4300 metric tons over five years.

Some typical SyncroSpeed installations.

One large multinational molder evaluated SyncroSpeed on a 550-ton Engel ES machine with two 55-kW motors molding polypropylene storage boxes with a 385g shot weight and 29.5-second cycle. Combined power draw at the start was 53.9 kW. With SyncroSpeed installed, energy use dropped nearly 47% to 28.6 kW. Within a year, installations were done on machines in that company’s other plants in Korea, India, and Mexico—more than 100 machines total, from 500-750 tons, 50 of them Engels.

Another molder tested SyncroSpeed on a 1000-ton three-motor Cincinnati Milacron machine making polypropylene toilet seats on 105-second cycles. Total starting motor power was 77.4 kW, which fell 44% to 43.4 kW when SyncroSpeed switched on. Annual energy consumption decreased by about 201,000 kWh, and CO2 emissions were down by 108 tons each year. The payback time was 16 months.

An 800-metric-ton KraussMaffei with a single 132-kW motor was producing ABS automotive trim parts in 61 seconds. Motor consumption before modification was 72 kW and 36.9 kW after SyncroSpeed was turned on—a 48% reduction. Payback time was 15 months.

Additional energy saved
Besides reducing the energy costs related to the molding machine itself, using SyncroSpeed also reduces the energy needed to cool the hydraulic oil because the oil does not get as hot. This is particularly true when a chiller is used. Further benefits include a quieter work environment and gaining tax credits and/or rebates from state governments and/or energy suppliers for reducing consumption.

One could ask, if this technology works so well, why don’t machine makers incorporate motor speed control into their presses? In fact, some do. Negri Bossi has motor speed control on its Vector Series machines, which it markets as very energy efficient. Wittmann Battenfeld offers it as an energy efficiency option on some of its systems. And many newer Asian-made machines feature fixed-volume pumps with variable-speed servomotor drives as an improvement over variable pumps and as a competitive alternative to all-electric presses.

SyncroSpeed, says its maker, does not fundamentally change the molding machine, and can be disengaged easily at almost any time. For instance, should a fault develop in the speed control software, pressing a single button can instantly bypass the speed control, letting the motor again run at full speed. Prior to installation, Knaster and his team do a detailed analysis, and based on the results provide a simulation that he says predicts with high accuracy the level of savings to be expected with a particular machine/job combination. Calculating ROI is then simple math.

Knaster notes that SyncroSpeed has always been fully backed. “If it doesn’t work, we take it back.” The company, he adds, has never taken one back.

An exception to the 
VDP exception
As a general rule, the makers of SyncroSpeed say the best results occur on a machine with a fixed-displacement pump, rather than a variable-displacement pump (VDP). A VDP acts similarly to the SyncroSpeed motor control, adjusting the pump so it functions on demand rather than at constant full speed. Savings also happen with VDP and fixed pumps on the same motor shaft.

SyncroSpeed’s Robert Knaster recently oversaw a test done by a molder that proved an exception to that rule. A VDP-equipped 725-ton Cincinnati Milacron machine was running a large part on a long cycle: 381 seconds. The press has two motors: 55 kW and 45 kW. Energy use per cycle had been 35.4 kWh, but with SyncroSpeed installed and operating, energy consumption decreased to 19.3 kWh, a 45% savings. Knaster says this should not be considered automatic, but it shows there can be savings, even when a press has a VDP.

“Assessments of complete plants with significant production hours, kWh cost of more than $0.07, and VDP installed showed the promise of savings, especially with rebates,” he adds. The ROI may be a little longer, but the savings start at installation and continue from there. —Rob Neilley

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