Flowfront: The magazine of choice for plastics professionals

the executive view - Energy savings: a new revenue source for molders

By Barr Klaus, Vice President, Technology, Milacron, Inc.

"Energy crisis" seems to wax and wane as a news headline, but anyone with more than a few years of business experience can see the long-term trend for energy costs is — and will continue to be — up, not down. For injection molders under pressure for cost reductions or "rebates" on past work, the recent California crisis helped bring into focus the painful reality that energy is one of the top three or four cost components of a molded part, and hydraulically powered molding machines consume about three times more energy than all-electric injection machines. It's now clear that the more efficient electric machine can put that operating cost difference right back on the molder's bottom line.

All this has been proven by independent tests, but few molders have considered the large-scale impact for the nation and their own businesses. Milacron estimates all-electric injection molding machines could annually cut 8.9 million megawatt hours of electricity from the process on a national basis —700,000 megawatt hours and $42 million annually in California alone.

Large companies realize there's a lot of energy money being left on the table, not just in molding, but throughout the enterprise. Many have mandated across-the-board energy reductions in their operations because they realize energy cost savings go straight to the bottom line. At three times the efficiency of conventional machines, new-generation, all-electric injection molding technology figures heavily in many programs. So to make electric molding more accessible and affordable for the industry, Milacron has opened the world's first Energy Resource Center for plastics injection molding.

The center addresses the interests of top corporate management, mold makers, financial executives, facility designers, utilities and energy aggregators/brokers, as well as molding managers.

We are teaming up with energy service companies who can package all-electric molding technology as part of a long-term operational cost solution that makes sense in the boardroom. This offers the industry a unique advantage for rapid integration and justification of all-electric molding for green-field plants.

The Energy Resource Center will assist in benchmarking an existing process against all-electric injection molding, with comparison of a wide range of cost and productivity factors. We're already working with energy service companies to give them the benchmark data they need to make sound financial decisions in helping their own customers design energy-efficient facilities or processes. For customers who need more data or assistance, the Energy Resource Center will run production lots of product or provide fee-based design services for re-configuring a plant for higher efficiency or creating a new plant on a clean sheet of paper.

All-electric injection molding machines were once considered "special purpose," but they've established themselves as the new standard in cost-effectiveness for any application. While they continue to increase market share in precision molding, they are more often used for ordinary products from automotive parts and cutlery to pet-food dishes and soft drink cases. In short, all-electric injection presses have turned a technology corner and are now measurably better than hydraulic or hybrid machines for mainstream applications.

The four independently powered and controlled axes of electric injection molding machines overlap the functions of clamp, injection, extrusion, and ejection, giving a molder lots of ways to shave cycle time. And the direct, mechanical connections between motor and machine components mean drift-free, precision positioning for the clamp, screw, ejectors, and injection unit — nothing can move in any direction without a command from the control. Thus, pre-injection and coining are standard capabilities on most electric machines.

In fact, all-electric presses outperform hydraulic and hybrid machines in a number of key areas, even high-speed packaging applications. It's a real eye-opener for a packaging tool-maker to see an electric machine run stack molds and inject at 100+ in3/sec. At NPE 2000, a 550 ton electric machine molded 5-gallon buckets with an injection unit capable of 600+ lb/hr throughput, speeds of 521 mm/sec, and pressure to 27,500 psi. And the "speed record" for injection belongs to a newly developed electric machine with linear motors on the injection axis: 2000 mm/sec for "paper-thin" molding.


Milacron’s MasterPowerline 330-M	Milacron’s MasterPowerline 550


Powerline 935

This new breed of electric machine is no longer a limiting factor on cycle time. It's not uncommon for an all-electric machine to “outrun” a mold that was already taxing the limits of a high-performance, accumulator-boosted hydraulic machine, which shifts the focus of the process design quite a bit.

Mold design can be simpler and less expensive for an all-electric machine as well, because independent operation of clamp and injection allows parting-line venting during tonnage build. This reduces cost and time for excessive or difficult mold vents. Venting during pre-injection means there's less resistance in the mold; fill times are shorter. Hot gas that can overheat the mold or melt is relieved. And mold maintenance is reduced because plasticizer does not build up so quickly in the vents.

Precise control of mold position also reduces wear, especially for stack molds, allowing more design freedom and lower cost. Higher cavitation or larger parts can often be accommodated in the same clamp area, too, because the precision shot control on an electric machine typically reduces clamp force requirements.

Electric injection molding machines continue steady market penetration in the USA (30+%) and Japan (70+%) as energy costs rise and cost gaps between electrics and hydraulics decline. The only disadvantage of electric technology is that, ton for ton, ounce for ounce, the equipment has a higher initial cost. Despite an initial cost premium, electric injection molding machines cost so much less to operate that real savings accrue from the very first part molded on the machine, rapidly offsetting the difference.

Can the "more expensive" machine actually cost less to own long term? The market has already decided that it does. For more information on Milacron’s products and technologies, contact them at +1 513-536-2584 or visit their Web site at plastics.milacron.com.

The 7 Arguments for All-Electric

There's no warm-up, no delay in waiting to find out what quality of part will be produced on the machine that day. Output is usually stable and predictable after the first 3-4 parts, as well as after 4-5 years
.
Material use can be lowered, close to the threshold of a short shot, without exceeding that threshold.
There's no expense for cleaning, storage, disposal, or maintenance of hydraulic fluid.
Air conditioning load on the plant is greatly reduced.
Low noise levels (<68 dBA) allow more flexibility in plant layout, siting other functions or facilities near molding machines.
For new construction, electrical service to the plant can be reduced about two-thirds, tower water requirements reduced, and plumbing reduced.
Faster cycles are achieved due to the inherent ability to overlap functions.