Electric injection machines inspire respect, loyalty

All-electric and hybrid-electric injection molding machines once evoked doubt and reluctance, but they are now becoming entrenched in the market. A sampling of molders tell us why.

Over the last three years, about 29 percent of injection machines sold in North America have been of electric rather than hydraulic design, and that number is growing, according to Agostino von Hassell of The Repton Group, New York, NY.

Since 1985, when Cincinnati Milacron (now Milacron Inc.), Batavia, OH, led the charge by bringing Japanese-built Fanuc all-electric machines to these shores, about 30 other machine builders have gotten into the electric machine business as well. The list provides names and telephone numbers of those companies, along with an indication of whether they supply all-electric machines, hybrid-electric machines, or both.

Initially, all-electric machines were available mostly in small sizes such as 50 or 100 tons. The market is still dominated by small or medium machines, but larger machines are now offered. Several builders make all-electrics in the 1500-ton range, and at least one 2000-ton all-electric, which will be the largest all-electric on the market when it is completed, is on the way from Ube, Ann Arbor, MI.

For the uninitiated, the term "all-electric" implies that both screw motion and clamp motion are actuated directly by electric motors, usually a-c servomotors, without any intervening hydraulics. The "hybrid" machine normally uses an electric motor to drive the screw, but uses hydraulics on the clamp end of the machine. Even hydraulic, toggle, and hydromechanical machines require electricity to operate, of course, but they also require hydraulic oil and hydraulic circuitry.

The usual mantra from suppliers of the all-electric machines is that their units use less electricity than the hydraulic designs, are cleaner because they use no hydraulic oil, run quieter, are more precise, and require less maintenance. Unfortunately, they also cost more, a premium cited by purchasers as ranging from 10 to 20 percent.

To get some other perspectives on all-electric and hybrid electric machines, we went to a number of molders who are using the machines and are willing to share their observations. While not perfect, their experience has been overwhelmingly positive, which bodes well for the future of the electric machines.

Debuting a Hybrid

Robbins Scientific, Sunnyvale, CA, has about 100 employees with molding and assembly divisions combined. It runs 20 injection machines and has just dipped into the electric injection technology by acquiring a single 100-ton Husky hybrid machine. (Husky does not supply all-electric machines to date.)

The machine is used to mold medical pipette tips and tubes in PP and other polyolefins. Wittmann (Torrington, CT) robots are used to handle parts from a mold that runs 32 parts per cycle with 16 sprues. According to Jesse Cohen, senior process engineer, the machine was acquired for its tiebar spacing, thin-wall capability, and ability to run with automation. The energy efficiency of the hybrid was tested using a kWh meter and then compared with the power consumption of a comparable hydraulic machine. Power consumption of the hybrid machine was reported to be considerably less.

Robbins got the unit as a beta machine while development and testing were still under way, and benefited from a discount accordingly. Performance of the machine ultimately prompted the company to keep the press.

Due Diligence First

Inland Technologies, Fontana, CA uses 30 machines, 15 of which are all-electric. The all-electrics range from 55 to 120 tons; the other machines are toggle-clamping units ranging from 55 to 85 tons. Annual sales for the company, which employs 75, are $13.2 million. Every machine is equipped with a robot or sprue picker. In addition to injection molding, the company performs moldmaking and assembly.

Gary Hengeveld, vp, and Glenn Crossno, president, run the operation in an entrepreneurial fashion, with an eye on long-term results, rather than as a publicly held corporate entity pressured to show favorable results every quarter, or even every month, to board members, stock analysts, and shareholders. Since they can tell the controller what to do, instead of vice versa, they are at liberty to spend a little extra money on electric machines now in order to reap what they expect to be long-term benefits. Inland reports the cost of its all-electric machines to be at a premium of 10 percent over hydraulics, with the cost amortized over seven years.

Before buying its first all-electric machine, Inland conducted a due diligence side-by-side trial of a JSW press vs. a machine we will describe as "Brand X." Hengeveld notes that virtually any manufacturer of an electric machine will supply one essentially free for a trial, provided that the molder pays for the shipping costs.

Inland, which is an all-JSW shop, continued to favor the control package of JSW. It found differences in the knockouts and machine uptime between the JSW and Brand X units. Brand X also had valving problems and sensor faults. Although Inland clearly went into the test with a preference for JSW, it attempted to make the comparison as objective as possible. (Hengeveld notes that in the interval since the test, Brand X has cleared up the problems identified during the test. In fact, Hengeveld has a friend in the molding business whose shop is exclusively equipped with Brand X machines.)

Inland?s practice is to run parts in the all-electrics that require tight tolerances. Precision molded parts are produced by all-electrics running in a Class 100,000 cleanroom. Applications include health care (especially miniatures), which is 75 percent of the business, plus electronics, automotive, and fluid handling, such as valves and irrigation fittings. Materials range from PP to PEEK.

When Inland?s electricity supplier (Edison) gave it a rebate to perform a study of electricity consumption, it found that the all-electric machine is 16 percent more energy efficient than a comparable hydraulic. Other advantages of the all-electric machine include cleanliness (no oil), practical elimination of noise, cooler operation, and excellent repeatability. Also, because the electric motors run cooler, Inland hasn?t needed to upgrade its chiller system, which would involve costs for chemicals, energy, and chillers.

All-electric in 1994

ABA-PFT in Manchester, CT went all electric in 1994. The plant, which has 50 employees and generates $9 million to $10 million in annual sales, has 16 all-electric Milacron Roboshots (14 55-tonners and two 110-tonners). Fourteen more (three 110-tonners and 11 55-tonners) can be found at the company?s Vernon, CT plant. According to Dave Shepard, molding manager, and Sam Pierson, president, ABA-PFT was the first to acquire all-electric Roboshots for production in the U.S.

The company?s love for the all-electric began at NPE in 1994, where the technology was considered key to establishing lights-out operations. All in all, the company has been very happy with its all-electrics since then. In fact, except for specialty applications like two-shot molding, all future machine acquisitions are expected to be all-electric.

Early machines, says Shepard, were "not great at mold protection," but with current machines, he says that is no longer a problem. And while the company keeps a cache of spare parts on hand to enhance their ability to repair the machines, Shepard and Pierson say it?s rarely required. Shepard also points to the Roboshot?s cushion control as a standout benefit. The only potential problem cited was that all-electrics are susceptible to power blips, which can result in a loss of power supply.

In the future, the company plans to add further automation to its Roboshots, including Wittmann servo robots.

One "So Far"

Beach Mold of Emporia, VA is just getting started with all-electrics. The company, which operates with about 125 employees at the Emporia location, has 22 machines, but only one all-electric?so far. Standing alone is a Milacron Powerline 440-ton machine. The machine comes equipped with the Sidewinder option, which uses a plunger/shooter combination to increase consistency of shot size over a wider range of capacity, as compared to a single reciprocating screw.

According to Kevin Mullis, manufacturing engineer, Beach Mold paid a 20 percent premium over the cost of a hydraulic machine for the Powerline. What it wanted was speed and consistency. In fact, when asked about automated discrimination and separation of bad parts on this machine, Mullis explains that with the Powerline, "we don?t make bad parts."

Furthermore, he says the machine is at least 10 percent faster than a comparable hydraulic, and with the right robotics, 20 percent faster. Electricity savings is also a bonus. As long as it can get the machine size it needs, Beach Mold plans to continue buying all-electrics in the future.

Relationships are Paramount

World Class Plastics, Russells Point, OH, is a privately held operation that does about $10 million in sales, has 67 full-time employees, and occupies about 32,000 sq ft of molding space, plus another 10,000 sq ft for toolmaking. An expansion of an additional 30,000 sq ft is planned during the next 12 to 15 months. The company does medical, automotive, industrial, and appliance molding, specializing in visually critical parts with demanding tolerances. Pad-transfer printing and assembly are included. Materials include PS, LDPE, acetal, nylon (including glass-reinforced nylon), PVC, ABS, acrylic, and PC.

World Class has two all-electrics in-house, along with 24 other machines. Both electrics are 100-ton Sumitomos. The first one was acquired about 12 months ago, and the second one more recently. One of the electric machines is working on a project involving a dental part requiring dimensional tolerances of ±.001 inch for which the original cycle-time target was 12 seconds. The all-electric is beating that target. The machine is served by a Yushin (Cranston, RI) servo robot and a discriminating conveyor. The other all-electric is producing automotive clips and fasteners.

Steve Buchenroth, president, and Scott Wisniewski, vp of engineering, are co-owners of World Class, and report that, based on their experience with the all-electric machines, they could save $6000 to $7000 a month in electric utility charges if all of their machines were all-electric. That won?t happen right away, however, as the rest of the company?s machine fleet is relatively young and in good shape. The company aggressively pursues a preventive maintenance program with all of its machines but will use any replacement or expansion opportunities to buy more electric rather than hydraulic machines.

Notwithstanding a "nothing matters but price" attitude that prevails in some parts of the business community, World Class accepts a price premium of about 20 percent that applies to their all-electric machines as compared to hydraulic equivalents. Of course, the company fully expects to more than make up the price difference over the life of the machine in reduced electric, water, maintenance, and cycle-time costs.

The water savings are attributed to the lack of a need to provide cooling water to hydraulic motors, since there aren?t any on the all-electric machine. Being spared the need to install additional water capacity reportedly can save tens of thousands of dollars.

"Relationships are paramount," in business, according to Buchenroth, and that applies to both suppliers and customers. World Class runs exclusively Sumitomo machines (except for one vertical shuttle unit), and when the company decided to go the all-electric route, it did not conduct side-by-side tests with machines of any other brand. Its employees find the all-electric control systems easy to work with, and there is little or no incentive to change brands.

Targeting Preforms

Pretium Packaging, St. Louis, MO, a large 10-plant blowmolder, has ordered Milacron?s new E-PET machine, which is reported to be the industry?s first all-electric preform machine. It goes to Pretium?s Pointe Claire, PQ plant.

The 400-ton E-PET (110-oz shot capacity) joins six hydraulic Milacron preform machines at the Point Claire plant. Acquired from Duopac in mid-2000, the plant specializes in wide-mouth PET containers for the food industry with neck diameters ranging from 38 to 110 mm.

A patented two-stage, electric injection unit is reported to provide shot-weight repeatability of ±.05 percent, which will help Pretium eliminate wasteful overpacking and cut resin consumption, according to Richard Dube, director of PET Strategies.

To speed cycle time, the E-PET provides a separate inline packing pot for the two-stage injection unit. It delivers pack and hold pressure to free the extruder and injection barrel for immediate refill after the shot.

The 90-mm extruder can process up to 700 lb/hr. The injection unit?s 110-oz shot capacity provides a 68 cu in/sec injection rate and maximum pressure of 16,500 psi. Running a 48-cavity preform mold for a 16-oz bottle, the E-PET produces about 15,000 preforms per hour.