The question of hydraulic presses' continuing relevance is raised once again. If they are old news, why? If not, why not? In this two-part discussion we first focus on the injection molders and machine manufacturers who stand by their hydraulics, and hear their arguments in favor of the technology. In the November/December issue we'll hear from the molders and manufacturers who disagree.
|Engel showed there's a lot of life left in full hydraulic technologies with its 990-ton Duo twin-platen multimolding system. Try fitting a 990-ton all-electric toggle with a rotating platen in this compact footprint.|
Nevertheless, once they calmed down we got some very fresh and thought-provoking comments from the field. Before presenting what they had to say, some definitions are in order. Our questions concerned full hydraulic presses?those with a hydraulically powered shooter and a straight hydraulic clamp, not hydraulically powered toggle-clamp machines or hybrids.
After reviewing the responses, we stretched things a bit to include the hydromechanicals, which may use a little juice to power a mechanical clamp-locking mechanism, and hydraulically powered twin-platen machines.
|WHO'S WHO IN FULL HYDRAULICS|
AmeriPlas Machinery Corp.
|Autojectors Inc.||http://plastics.milacron.com/ |
|Battenfeld of America Inc.||www.battenfeld.com|
|Boy Machines Inc.||www.boymachines.com|
|Demag Ergotech USA||www.demag-ergotech-usa.com|
|Ferromatik Milacron NA||http://plastics.milacron.com/ |
|Hettinga Equipment Inc.||www.hettingatechnology.com|
|Husky Injection Molding Systems||www.husky.ca|
|Illinois Precision Corp.||www.illprec.com|
|Jaco Mfg. Co.||www.jacomfg.com|
|Jon Wai Machinery Works||www.plasticscommerce.com/jonwai|
|LG International America Inc.||www.lginjection.com|
|Lien Fa Injection Machinery||www.lienfa.com|
|Mitsubishi-MHI Injection Molding Machinery Inc.||www.mhiinj.com|
|Mini-Jector Machinery Corp.||www.mini-jector.com|
|Mir USA Corp.||www.mirpresse.it|
|Multiplas Enginery Co. Ltd.||www.multiplas.com.tw|
|Nissei America Inc.||www.nisseiamerica.com|
|Nissin Machine Co. Ltd.||www.nissin-mfg.co.jp|
|Sandretto USA Inc.||www.sandrettousa.com|
|Sumitomo Plastics Machinery||www.sumitomopm.com|
|TMC Jiangmen Magnetics& Machinery||www.tmcint.com|
|Tomken Tool & Engineering Inc.||www.tomkentool.com|
|Van Dorn Demag Corp.||www.vandorndemag.com|
Like many other injection molders responding to our questions, Curt Watkins, president of Alltrista Unimark (Rye, NY), says full hydraulics are here to stay, at least for now. "From a president's perspective, I would, in response, ask you a question: Is the internal combustion engine yesterday's news?"
Watkins offered three reasons why he thinks there's still a tomorrow for hydraulic presses:
"I feel that current hydraulic technology will continue to be driven to higher levels of performance and economy by the growth of the electric technology, in the same manner that internal combustion engines are being driven to new levels by the hybrid and total electric technology offerings," Watkins says.
Still, he shifts gears a bit in his conclusions. "However, I would like to clarify that I do firmly believe that the electric technologies are the wave of the future, just as the PC eventually outpaced the mainframe. That's outpaced, by the way, not replaced."
Trevor Spika of micromolder Makuta Technics (Columbus, IN) also believes that although it may be too soon to sound the death knell for full hydraulics, it could be sounding soon. "Our hydraulic machines are not quite as precise as our electric, but they are still a more robust machine in the same tonnage range," he says.
"We have not seen the electric systems perform as strongly as the hydraulics yet. However, this will most likely change in the near future."
Dale Smith of Technical Industries Inc. (Canton, CT) is another full hydraulics micromolder who's giving all-electrics a go. Smith agrees that hydraulic presses are still a viable alternative, especially when it comes to reliability. "We have excellent-performing hydraulic machines with over 25 million cycles. For us, this makes our all-electric an unproven machine.
"The mold protection capabilities of a hydraulic machine also is a known factor for us." Smith says there are still unknowns surrounding the electrics and adds, "We are familiar with the setup of a hydraulic, which makes us less prone to making mistakes."
TII's strategy is to buy all-electrics where they make economic or processing sense, says Smith, but the company has no intention of going 100 percent electric at this time.
Turning back to bigger machines and bigger parts, Russ LaBelle of Wilmington Machinery (Wilmington, NC) has something to add about the maintenance advantages of full hydraulic presses. "The ability to take a single motor with a set of hydraulic pumps and rotate the feedscrew, actuate the injection ram, open/close nozzles, open/close a press, provide core pull actuation, and open/close a safety gate is tough to beat by either all-electric or hybrid approaches."
LaBelle says that when you add features such as cavity pressure feedback and mold protection, the capabilities of fluid power go on and on, but he adds a note of caution. "This could change, of course. When and if all-electric control and actuating devices come along that match the simplicity, cost, and performance of hydraulic devices such as cylinders and valves, designers will be quick to apply them. These devices are lacking today."
Maintenance of all-electric machines may in the long run be simpler, LaBelle says. "However, today's maintenance person is more mechanic than electrician or electronics guru, for that matter. There will be the need for a different type of person, probably of greater skills."
|Van Dorn Demag sources say that presses 300 tons and less will probably all be all-electric in the next five to seven years. More than 300 tons, full hydraulics, like this Spectra 880, will remain as more affordable alternatives.|
Joel Thompson of Twinshot Technologies & Community Products (Rifton, NY) thinks there is still plenty of news in full hydraulics. "It's just a fact that plastic melt is a high-pressure liquid, and therefore the molding process itself will always be hydraulic.
"Take clamping for instance," Thompson says. "What better way to oppose the force of a large liquid-filled cavity in the mold than another matching liquid-filled cavity, as in a hydraulic cylinder? Especially in large machines, the benefits of hydraulic clamping over toggle clamps have been well proven. Suddenly toggles are back in style, only because you can't do anything else with an all-electric?not because it's better."
Thompson says electric drives are superior at controlling position and its associated derivatives, velocity and acceleration. But he believes electrics are inferior to hydraulics at controlling pressure.
"Since the molding process is based just as much on pressure as on position, there's something to be said for both," says Thompson. "In the end, even a hydraulic machine is electric. But the conversion from electrical, through mechanical, to fluid power happens earlier in the process."
|Sources at LG International, manufacturers of a line of full hydraulics, say all-electrics have technical limitations that restrict their use to only specific injection molding applications.|
There is no one machine on the market that can compensate for the human element, says Don Hardin of Fabrïk Molded Plastics (McHenry, IL). He adds that state-of-the-art repeatable machines are crucial to the overall process, but you can't overlook the need for good plantwide process and quality control.
"I think it has been proven that the linear repeatability of the electric machine is superior to that of the hydraulic machine," Hardin says, "but there are other molding-related factors involved that affect the quality of the finished part, such as inconsistent nonreturn valves, inherent lot-to-lot viscosity variation of plastic resins, and the natural unbalanced flow that takes place in multicavity molds."
Fabrïk has found the use of cavity pressure control yields very good results. Hardin says the cavity-pressure transfer method compensates for the varying viscosity and inconsistent nonreturn valves.
|Ferromatik Milacron, like many other OEMs, offers a diverse selection of machines with several different types of drive systems for its customers, including its European-built K-Tec line of high-performance hydraulics.|
Though it also produces hybrids, John Ward of Van Dorn Demag Corp. (Strongsville, OH) says Demag Ergotech GmbH fully intends to produce presses capable of meeting both the simplest and the most demanding applications of custom molders, as well as specialized segments of the injection molding industry, and that includes full hydraulics.
"We will continue to design and build machines that lead the industry, but not for the sake of technology. At this time if you do not want to compromise performance, you have to compromise on the combination of drives available," Ward notes.
He says full hydraulics can only become obsolete when all-electric technology advances to become the most cost-effective solution for meeting all the processing demands of the market. "We will continue to bring new products to market, but not as a 'me-too' approach."
Mark Zulas of Niigata Plastics Machinery (Itasca, IL) agrees. "As I am sure you are aware, the latest and greatest new toy gets all the press. As for hydraulic molding machines being obsolete, my personal opinion is no. There are still parts that require a hydraulic machine's ability to maintain an extensive amount of injection pack and hold pressure for a period of time that cannot be achieved by an all-electric molding machine."
Zulas says that most of these molds could be modified to run on an electric machine with faster cycle times, but convincing a supplier to pay for a mold modification is, to put it mildly, "frequently impossible."
"Also, molds with large hot runner systems require a large amount of nozzle touch pressure to the mold," he says. "Many electric molding machines have a smaller amount of nozzle touch force when compared to the hydraulic equivalent. Our company had to address this issue many years ago, but much of our competition is still trying to figure it out."
|Nissei sources say full hydraulics will survive well into the future, especially in applications requiring ultrahigh-speed filling. Its UH 2000, possibly the fastest production machine in the world, has a 2000-mm/sec injection rate.|
Mention of the "cost-effective solution" raises a major point of the full hydraulics partisans, namely the high price of all-electrics. Mark Sporysz, of molder Caplugs (Buffalo, NY), says full hydraulic machines will be around for a very long time. "Electric machines have their place. It's clean molding, with no oil or tower water," he says. "But hydraulic machines are durable and repeatable with a proven track record. And mechanics are trained to service hydraulic machines."
The best way to compare machines is over a time span of about eight years, according to Sporysz. "Compare the machine purchase price to the maintenance and downtime cost, along with energy consumption. This answer may vary from machine manufacturer and molding application."
Price is one of the major reasons why Neal Elli of Empire Precision Plastics (Rochester, NY) says hydraulic machines are still a viable alternative today. "They are tens of thousands of dollars less than electrics, and they are sufficiently fast and flexible enough for many applications," Elli explains.
He says good hydraulic machines also can be reasonably energy efficient, especially considering the cost of power in most locations such as the Midwest and South. He also believes that the fastest machines will still need to run hydraulically.
"The cost of the electric machine would need to drop almost 25 percent to make a big negative impact on the sales vs. hydraulic," says Elli. "If and when this occurs, then the hydraulic machine will really start to decline."
Kurt Kendall of Motor City Plastics (Dundee, MI), which specializes in the high-speed/thin-walling of cosmetics packaging parts, says that hydraulic presses will survive as long as they are less costly to buy and are well-suited to applications that are not very demanding. He says the fast cycling and precision that high-speed electrics provide "will not make a hill-of-beans difference in a less demanding application."
"However," Kendall adds, "if the market brings pricing down on all-electrics, then this could be the beginning of the end of the hydraulic squeeze-and-squirts in the 1000-tons-and-down range." He thinks OEMs should be able to build electrics for less when using mass-assembly economies of scale.
|Sumitomo plans to convert its smaller-tonnage series of hydraulic machines, like this 50-tonner, to all-electrics, and has begun building them in Georgia. But it's keeping its larger-size hydraulics, from 100 to 350 tons, at least for the time being.|
Robert Koch, president of Boy Machines (Exton, PA), takes up the cost issue with concern. He says that one of the major selling points of all-electrics is their energy efficiency and admits that they can generate power savings. However, he says, there's a big but. "When you measure the energy usage of some all-electrics and a fully hydraulic Boy, then compare prices of the two machines, energy doesn't accrue through to the bottom line. The ROI you can expect is 32 years with one all-electric . . . 23 years in another case, in our machine size range, which is under 100 tons."
Koch says that rather than ask how much a machine costs, the real question should be how much does it cost to make a part? "Ultimately, when you're talking about paying $40,000 for a machine vs., say, $80,000 for a comparably-sized all-electric, how can you possibly select the all-electric machine on the basis of cost per part?"
Since he came on board in April, he's visited several customers of Boy Machines and has asked them how they cost-justify purchasing an all-electric machine that's often double the cost of a full hydraulic. "What can you afford to pay to get the same quality part?" Koch says he has asked them. "When the fully hydraulic machine makes a consistently good part, isn't that all it's about?"
Koch also is concerned about states that award tax subsidies to molders who purchase all-electrics, just because they are perceived as being more energy efficient. "That's unfair," he says. "These rebates shouldn't be based just on the price of a machine. That drives people to buy all-electrics in a vacuum.
"What are the comparative savings?" he continues. "What are they comparing it against? These rebates should be based on a fair comparison of the two different technologies when it comes to the energy required to run a part. They should run a part on a MY2002 all-electric, then run the same part on a MY2002 fully hydraulic to calculate rebates."