Canadian Plastics

INJECTION MOLDING GETS TRIM

Depending on which injection molding shop you talk to, the Great Recession may or may not be over. But one thing they'll all agree on is the need to get more out of their I/M machines -- more parts pe...

September 1, 2010   By Mark Stephen, Editor



Depending on which injection molding shop you talk to, the Great Recession may or may not be over. But one thing they’ll all agree on is the need to get more out of their I/M machines — more parts per hour, more resin savings, more energy savings. Taking the last first, energy savings has been the hot topic for awhile now — and if you haven’t been living under a rock, you know that OEMs have spent the past few years unveiling new energy-efficient machines, one after the other, at an almost frantic pace.

Developments that save material usage, cut cycle times and improve overall cost haven’t received quite the same share of the spotlight, but they’ve been a focus for OEMs nonetheless. Here are some recent results.

EXCELLENT ALL-ELECTRICS

Wittmann Battenfeld GmbH recently redesigned the former Battenfeld Microsystem five-ton I/M machine and has come out with two models of the new all-electric MicroPower series in five and 15 metric tons.

According to the company, the MicroPower machines are designed for precise metering of material for high-precision and micro parts — and even nano parts — with accuracy of 0.005 grams. And the units are fast: Injection speed and pressure can be up to 750 mm per second and 36275 psi.

The keys to resin-savings? A two-step screw plunger system that’s designed to empty on each shot, with no material left over. Shot capacities are 1.2 and 3 cc, although shots as small as 50 mg can be delivered. The units are also said to deliver up to 90 per cent material savings in gating.

“Apart from the fast acceleration and precise metering, the main benefit of the MicroPower series is its cost- efficiency,” said Rob Miller, president of Wittmann Canada. “Thanks to shorter cycle times as well as lower material and energy consumption, cost savings of about 30 to 50 per cent can be realized when compared to conventional machines. With such drastic cost cuts, the payback period for this system is extremely fast.”

For injection molders in the packaging industry, there’s more good news on the speed front: Engel’s new e-cap system, said to be the first fully electric system for cap and closure molding, is designed to cut energy consumption in half while also providing speed competitive with standard accumulator- assisted hydraulic cap-molding systems. It has a new injection unit capable of high plasticating rates, and high-speed, high- pressure injection of up to 300 mm per second at 29,000 psi in the premium version, according to Engel. The first model will be 420 metric tons, and capable, the company said, of molding 26-mm soft-drink caps in 96 cavities with a 2.6-second cycle.

“The e-cap has the potential to bring faster cycle times and higher outputs to the hugely expanding plastics caps and closures markets — the fastest growing niche in the overall plastics packaging market,” the company said.

JSW Plastics Machinery, meanwhile, has added new medium-to-large sizes to its AD Advantage series all-electric molding machines in clamping forces of between 550 to 850 metric tons. Design improvements are said to include cutting dry-cycle times by 20 per cent, while newly developed injection units are smaller and lighter to improve acceleration and deceleration, reducing plasticating time by 10 per cent.

HELPFUL HYBRIDS

Also targeted at reducing cycle times is Arburg Inc.’s Allrounder H (Hidrive) series hybrid machines, introduced last year. Presently consisting of five machines ranging from 600 to 3,200 kN, the series pairs a servo-electric clamping unit, as already used in the company’s Allrounder A series, with a hydraulic unit, as used in the company’s Allrounder S series.

With an injection unit complemented by a hydraulic accumulator, the H series machines are said by Arburg to generate the high injection speeds required for thin-walled packaging and other applications, but are priced about 25 per cent less than the firm’s Alldrive all-electric machines. And, yes, for those who are interested: Energy savings of up to 40 per cent can be achieved, because in addition to the servo-electric drive and braking energy recovery, the hydraulic accumulator is also driven with the minimum amount of installed pump capacity and by motors of efficiency class EFF1.

The new El-Exis SP (speed and performance) series hybrid machines from Sumitomo Demag, available with clamping forces from 150 to 750 tons, are designed to cut cycle times for packaging applications. “The direct drive for dosing is frequency-controlled, giving a higher plasticizing output, which gives a shorter cycle time,” said Andreas Schramm, head of research and development. “At the upcoming K show, we’ll be running an El-Exis SP 300/2500 press to produce an HDPE-threaded cap weighing 1.6 grams formed in a cycle time of only 2.6 seconds.”

Crucial for shaving seconds off the cycle time, Schramm continued, is finding the correct balance between acceleration and mold braking. “For an in-mold labeled part, for example, acceleration must be high, but mold braking is probably going to be more crucial,” he explained. “By contrast, a thin-walled yogurt cup to be labeled or printed after molding could be run at higher acceleration rates.”

Nissei Corporation has made similar improvements to a wide range of its machines. “The PNX, FNX, and FVX hybrid model Nissei machines have an injection scanning time of 250 micro seconds, while the Nissei NEX all electric machines have an injection scanning time of 100 micro seconds,” said Brad Lemieux, sales manager with Nissei representative En-Plas Inc. “These fast scanning times allow the machine to react faster to changes that could affect the injection process control, maintaining a much more consistent cycle and part integrity through their shot to shot repeatability. This is especially important in circumstances where larger parts are being molded — inconsistent deviations in part weight could easily add up to a lot of material, and therefore money, being wasted.”

Importantly, the presses permit ejection on the fly, for up to 10 per cent faster cycles. “The NEX also has injection holding pressure positioning control — or HPC — which maintains uniformity of thin-walled parts and prevents sink and warpage in high-speed molding applications,” Lemieux added.

RIGHTEOUS RETROFITS

Finally, lest you think you have to buy the newest equipment to get some of these benefits, relax — in some circumstances, retrofitting can do the job. Introduced in June, Husky Injection Molding Systems’ Encore program is a low-investment tooling and machine upgrade program designed to help customers improve systems performance — including getting faster cycle times — on injection molding machines that are less than 20 years old.

The program can include both tooling and machine upgrades and is broken down into two distinct series: maintenance, meaning reliability upgrades done over time for systems where performance improvements are not needed; and performance, a more complete upgrade that does include some new technology, including Polaris controls.

RESOURCE LIST

Arburg Inc. (Newington, Conn.);

www.arburg.com; 860-667-6500

Dier International Plastics Inc, (Unionville, Ont.); 905-474-9874

D Cube (Montreal); 514-272-0500

Engel Canada Inc, (Guelph, Ont.); www.engelglobal.com/na; 519-836-0220

Husky Injection Molding Systems (Bolton, Ont.); www.husky.ca; 905-951-5000

JSW Plastics Machinery Inc. (Elk Grove, Ill.); www.jswpmi.com; 847-427-1100

Nissei Plastic Industrial Co./En-Plas Inc. (Toronto); www.en-plasinc.com; 416-286-3030

Sumitomo (SHI) Demag/Plastics Machinery Inc. (Newmarket, Ont.);

www.pmiplastics.com; 905-895
-5054

Battenfeld (Wittmann Canada Inc.) (Richmond Hill, Ont.); www.wittmann-canada.com; 1-866-466-8266


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