Hybrid vs. electric injection molding machines: Debate continues

- Price, energy efficiency, ability to handle specialized in-the-mold actions all factor into decision

LS Mtron is pushing the limits on expectations regarding the maximum size of all-electrics. Its newest 1,500-ton LSG-E injection molding machine likely will be available in the U.S. starting next year.

Like the debate between dogs and cats — or the choices we face in the November elections — injection molding machine (IMM) buying sometimes comes down to what looks like a binary argument:

Electric vs. hydraulic?

While manufacturers continue to roll out new machines that reflect demand for electric IMMs — including, most recently, an electric IMM series from Boy and, in the future, a 1,500-ton all-electric press from LS Mtron — OEM representatives say what kind of machine you choose comes down to balancing factors like energy consumption, price, precision and cleanliness.

They say many of the old tropes — that hydraulics are bigger or cheaper, for instance, or that electrics are cleaner — just aren't so clear-cut anymore.

“There is a very interesting notion that the molding machine market has about electric machines being more energy-efficient than a servo-hydraulic machine. They're not. They're really only about ... 5 or so percent more energy-efficient than a servo-hydraulic. Granted, compared to an old-school classic hydraulic machine, they're about 50 percent more energy-efficient,” said Ben Hartigan, marketing coordinator for the Absolute Group of Companies, which in North America sells Haitian IMMs as well as a line of robots.

Depending on the supplier and application, perceptions about electrics, hydraulics and hybrids vary.

Plugging in

Some representatives suggest going all the way — all-electric — while others, like Hartigan, tout a more-measured approach. On one end of the spectrum are LS Mtron’s Peter Gardner and John Wiley, who are proponents of all-electrics.

"More customers, as they're replacing older hydraulic machines that have come to the end of their life, [are] replacing them with electric. And that's been kind of a no-brainer for, say, smaller machines,” said Gardner, president of the U.S. subsidiary of the South Korea-based company.

Over a long career that included about 20 years at KraussMaffei. Wiley, who serves as LS Mtron’s director of customer service, has overseen a lot of equipment installations and maintenance.

He asserted that all-electrics are more energy-efficient, using energy only when required, rather than continuously as hydraulics do. The servos allow the mechanisms governing movements such as injection to “hibernate” without drawing on power, he and Gardner explained.

The difference is especially noticeable in applications that require long cooling times, Gardner said.

“When things are cooling in the mold and you're not recovering on the screw side or on the shot side of the machine, the servo motors just are doing nothing,” Gardner explained, making them “very, very, very efficient, especially in the longer cycle times.”

“A traditional hydraulic machine will just run and spin the pumps, and your power consumption is going to be like 30 percent of maximum, so it's wasting energy, where the electric will go into hibernation mode,” Wiley said.

Compared with a 20-year-old hydraulic IMM, for instance, a new all-electric uses about half as much energy. For plants that have maxed out their energy usage, that’s a big consideration — it means they can accommodate more, new machines without more power.

“It doesn't tax their infrastructure in terms of the power consumption or the water tower on top of the building and their water distribution system. They're not having to add anything,” Gardner said.

But LS Mtron’s executives’ praise for all-electrics goes beyond energy-consumption benefits.

Generally, the machines have fewer moving parts, making them easier to install and maintain.

And while all-electrics offer more feedback and monitoring than hydraulics, from a mechanical point of view, the design “is rather simplistic,” Wiley said.

“It is interesting to mention that when you go with all-electric, there's less moving parts, so that also affects your performance, as far as maintenance, as far as unscheduled downtime, as much as your supply chain. You do not have to stock a tremendous amount of parts,” he said.

As an example, Gardner said a typical small hydraulic IMM might have 400 components, compared with only 100 for the same-sized all-electric model.

That extra complexity — along with hydraulic-specific tasks, such as replacing oil and bleeding air out of the system — contributes to a bigger burden for users of hydraulic IMMs.

By comparison, Gardner called all-electrics “plug-and-play.”

“I think we have seen a pro-all-electric sentiment, just because your MRO, just because of your preventative maintenance and your consumable parts are down. Traditionally on a hydraulic machine, you have to change the filters, you have to send your oil out for treatment. There's so many external costs other than the initial purchase, and then the initial purchase also comes into play, because you're not buying literally hundreds and hundreds of gallons of hydraulic oil at $8 or $9 a gallon,” Wiley said.

All that oil produces its own energy concerns — especially if you’re trying to maintain a comfortable environment for your workers.

“With the hydraulic reservoir, in years past, the tonnage pretty much mimics the oil capacity. So a 500-ton machine would take 500 gallons of oil, and if the oil heats at 110 degrees, that's 110 degrees at 500 gallons of oil, which is a tremendous heat sink, if you have a controlled environment production hall,” Wiley said.

It all adds up, Wiley and Garder said, to big savings.

According to an analysis provided by Gardner, over a year, an LS Mtron user would spend $6,698 related to the resources to run one of the company’s 386-ton all-electric IMMs, compared to $15,903 to run a hybrid or $23,771 for a hydraulic. Costs include electricity, as well as oil and water requirements.

Meet me halfway

But not everyone is sold is on all-electrics.

“I have to throw the stone that not everything [about] the electric machine is energy-efficient. But some of the [characteristics of] hybrids can be advantageous,” said Kohei Shinohara, senior VP for Sodick-Plustech.

For some, choosing the right machine type inspires a bit of ambivalence: It depends.

At Fakuma, Boy, which makes hybrids and electrics, rolled out a new machine series, the Electric. Clamping forces of the compact, two-platen servo-hydraulic machines in the series range from about 39 tons to 90 tons

They have electromechanical injection, dosing and ejector drives, so they can be classified as electrics, said Marko Koorneef, president of Boy Machines. But because they have a small hydraulic tank, they’re not all-electrics.

“Advantage of this machine is that if you need core pull in your tool you do not need to buy a separate hydraulic unit ( which are loud and dirty) to activate the core pull,”Koorneef said in an email.

By contrast, the company’s hybrid IMMs have a bigger hydraulic tank; they also come with a hydraulic ejector, but can be specified with an electric ejector.

After working with all-electrics, Koorneef said users sometimes shy away from them. On the other hand, users new to all-electrics tend to be more interested in them.

“Our advice to choose all-electric or servo-hydraulic would completely depend on the application the machine will be used for, and we advise our customer to take a serious and close look before making a decision based on market trend or feeling,” he said.

Nissei, which in 1983 first pioneered electrics. also makes a mix of machines that includes servo-hydraulics.

“What's your preference?” asked Joe Kendzulak, the executive technical adviser and GM of Nissei America. “The electric machine may run a little bit faster, or do you want a hydraulic machine that's a workhorse? That's how we offer up our machines.”

Typically, Kendzulak said, all-electrics cost about 10 to 20 percent more.

What customers decide is nuanced, he said.

“Some [sales] territories were 85 percent hydraulic being sold over the electrics, and then there's other territories more maybe it's like 60/40,” he said.

For Kendzulak and the Absolute Group’s Hartigan, precision and repeatability — rather than energy efficiency — are the strongest selling points of all-electrics.

"The people who really care about precision and repeatability are generally the smaller molders. So, 500 tons and under, we have seen a massive uptick in electric machines. I would say at least two-thirds of the market, if not more, will say, ‘Hey, we're going electric no matter what.’ And it makes sense ... repeatability, it’s a little cleaner, it’s quieter ... they all run perfect and nice,” Hartigan said.

But for molders who don’t need that level of precision, the drawbacks of all-electrics might outweigh the benefits.

To perform actions such as core pulls and other actions within the mold, which typically are hydraulically driven, molders with all-electrics must install a separate hydraulic power unit with a pump, which takes labor and space, he said.

“One of the big struggles in all-electric, a true all-electric, is that you can't really run these functions because you need hydraulic oil to move them,” he said. “So, a lot of the time, we'll see in these beautiful clean rooms, you’ll have this perfect, very expensive electric machine, and next to it is a gross hydraulic unit in a clean room ... leaking oil. It kind of defeats the point. So, the flexibility of hybrids, being able to run a lot of these hydraulic circuits, to run all these extra little doodad features, is a big deal that a lot of customers forget about when they're ordering all-electric.”

Shinohara echoed some of Hartigan’s sentiments regarding the superiority of hybrids.

“Our technology standpoint, or molding capability, machine capability, we still think our hybrid machine is a higher-performance machine with precision and performance. That's kind of our unique position — that electric is not the higher version of our machine line, but our hybrid has a higher-performance machine,” Shinohara said.

Meanwhile, Kendzulak voiced several concerns with all-electrics.

While the LS Mtron executives touted the maintenance benefits of all-electrics, Kendzulak said he sees them as less reliable, with more-demanding upkeep requirements.

“Usually, when people look at electric machines, some of our competitors, they only work on the electric machine for 10 years, and then they don't work on anymore because they say they're obsolete,” he said.

On the other hand, he said, “I have customers right around my office here, they have hydraulic machines from 35 years ago still running.”

Striking the right balance

OEMs have found ways to optimize the advantages of the different styles of machines so customers can enjoy the best of both worlds.

Can you really have it all?

As a representative of the world’s largest IMM builder, Hartigan thinks so — that the Absolute Group’s portfolio is big enough to accommodate most any need. The company produces a full spectrum of machines, from micro models to gargantuan workhorses, with a range of movement-mechanism choices. With its mammoth scale, it’s able to innovate efficiently, Hartigan explained.

When it comes to the electric-vs.-hybrid debate, size matters.

But so does the size of the supplier.

“The big break is once you get above 500 tons — a lot bigger parts, part dimensions get a little more tolerance-forgiving — so, it's not really as much of a precision thing; it becomes a cost,” Hartigan said. “And electric machines will go exponentially up in price as you go up in tonnage. Just the way the servo motors are designed, as they go up, it gets comically, exponentially expensive. Well, hydraulics is a very linear price scale. The splitting point is right around 500 tons, where, unless you need an electric, if you're going to buy a 2,000-ton molding machine, it's going to be twice as much to buy an electric machine and you're only going to get about less than 5 percent of performance difference.”

However, in its recent updates of its Mars and Jupiter lines of servo-hydraulic IMMs, Haitian has leveraged its own size to make the advantages of electric movement more accessible — even on bigger machines.

"What Haitian did with their most recent servo-hydraulic series is they changed the electric screw drive, which is the screw-rotate function, to be all-electric. And they did this without increasing the price of the machine — because of economies of scale, they found a pretty good, efficient way to build these kind of screw motors. So, Haitian essentially has a hybrid machine for that other hydraulic offering, [which] is really a hybrid with electric-screw rotate, which saves another 20 percent energy savings,” Hartigan said.

The world’s two best-selling IMM series, the Absolute Group’s Mars machines are available with clamping forces from 67 tons to 3,709 tons, while the two-platen Jupiter machines are available from 505 tons to 7,418 tons.

Finding your fit

Whether a hybrid or all-electric is right for you comes down to a number of variables, including the application. But just as the Absolute Group has done with its Mars and Jupiter IMMs, other OEMs continue to strive to accentuate the positives of the various approaches.

Like the Absolute Group, LS Mtron is pushing beyond the expected size restraints of servos. Gardner said he thinks there’s a demand for even-bigger all-electrics.

“The first buyers of the big-tonnage machines pay a pretty penny, I think, because there's just an economy of scale. There's not as many manufacturers of servo drives, servo motors, who make motors that are a big-enough capacity,” Gardner said.

But LS Mtron is pushing the envelope — it's preparing to launch its new 1,500-tonner, which likely will hit the U.S. market early next year, Gardner said.

Currently, “in our top range is the 950-ton electric, and we have quite a few of those being sold. But our customers are the ones pushing us to build even bigger. It's already built and being tested in Korea ... and then will be introduced in the United States,” Gardner said.

But will all-electrics ever overtake hybrids in popularity?

Even their biggest advocates — like Gardner and Wiley — aren’t sure.

“Energy is relatively inexpensive here in the United States, compared to other parts of the world, so maybe that's not the selling point. ... So, will it take off? I'm in my 37th year of injection molding,” Wiley said, “and I see every year, electric becomes more and more, but will it actually dominate the U.S. market? As Peter mentioned, I think I'll be long gone by then.”

* Source : https://www.plasticsmachinerymanufacturing.com/injection-molding/article/55238378/hybrid-vs-electric-injection-molding-machines-debate-continues