WHEN TWINS CONSUME LESS

Energy efficiency in manufacturing has become increasingly important with each passing year, for a number of reasons. Whether the primary concern is environmental (implementing a ?go green? movement within the shop), or whether it?s simply a cost-saving measure, today?s manufacturers are constantly searching for new ways to reduce energy consumption.

Fortunately, as manufacturers continue in their quest for smart energy consumption, new technological innovations are coming to light that can easily be implemented into machining operations.

Stama America, for instance, has been working on improving the efficient use of energy resources with their machining centers for over 25 years, and they?ve come up with several ideas. In their latest design, their new twin spindle machining center gives an example of how to dramatically reduce electrical and pneumatic energy consumption.

One way to conserve energy and promote efficiency is through multi-tasking; in other words, machining workpieces simultaneously. With these twin spindle centers, it?s possible to machine two identical workpieces at the same time.

The use of energy in this case is, on average, only 20 percent higher than with a normal single spindle machining center. The increased consumption is primarily from the second milling spindle. With twin spindle manufacturing, the overall energy consumption per finished workpiece is thereby 40 percent lower than with single spindle production.

For workpieces that can be machined on a four spindle machine, there is a provable reduction of nearly 60 percent in power consumption. An additional benefit to the synchronous manufacture of two workpieces in one work cycle is the automatic doubling in productivity, which leads to reductions in item costs.

So how does this process work? The created braking-energy is fed back to other components on the machine. This is made possible by state-of-the-art electrical drives. During deceleration, a demand for energy is created from the peripheral units, such as the hydraulic pump, air suction unit, coolant pumps, etc. The machine?s internal energy management system uses the gained energy from the braking systems and feeds that power directly back to the peripheral units.

The machine will not feedback or supply the public network with energy, but will utilize this energy, therefore reducing the demand for new energy. Without any agreements with the electric supplier, this allows the user to lower energy consumption and the associated costs.
Another example of energy conservation is one everyody is familiar with because we experience it everyday with our computers, cell phones, and various other devices: ?stand-by? mode. This is a standard energy-saving feature on any laptop, so why not use this technology in the job shop for machines?

Recently, Stama introduced their multi-step Standby Mode. In phases where the machine isn?t used for production for numerous reasons, the peripheral units (as well as the feed axes) can be shut-down sequentially. These machining centers are equipped for that scenario with an ?ECO-Menu?, where the factory setting for a timely stepped shut-down can be modified to the user?s own requirements. With this feature, a savings potential of up to 80 percent in power consumption can be achieved, and savings on energy costs can reach into the thousands of dollars per year per machining center.

Additionally, while in Standby Mode the machine can be activated without any time delay by pushing the start button. A self-reactivation is also integrated, and with that, for example, the coolant equipment can be set to a cyclic intermix of coolant water on the weekend, without having the full machine on-power during these non-productive hours.

That's not all. The design of work-zones for dry machining can contribute to energy savings. In wet-machining mode, the required amount of coolant to wash off and remove chips is noticeably smaller. A benefit is provided here in two ways.

First, the amount of water throughout the system and necessary consumption of energy are reduced. At the same time, the whole system can be designed smaller and more cost efficiently for lower investment costs.

Last but not least, it?s important to consider pneumatic energy into this equation as well. Compared to electrical energy, pneumatic energy is considerably more expensive. Its consumption at most companies is very often not evaluated because the related cost of pneumatic air is often underestimated.

Besides the use of air for actuators, compressed air is necessary to create positive air in machine elements to seal components against humidity. Having the positive air shut down with the machine could cause condensation on the cooling machine elements. Also, with the cooling process of the machine and ?thermal shrinking? in the sub µm range, a negative pressure can build up and suck in moisture particles. The positive air in the system is also necessary after the machine?s shut-down.

One solution to this comes in the form of a pneumatic-power-safe feature in which the air can be programmed to a certain time limit after the machine is powered off. The NC-control is not required for this action and the consumption of air energy can be reduced dramatically during off-shifts and weekend periods.

Achieving energy efficiency and reducing shop consumption is possible and easier to do than ever before. So whether the aim is to ?go green?, save some money on energy costs, or both, there are plenty of processes available to help achieve these goals easily while also increasing shop productivity. Multi-task, consume less, and save some "green" by going green.

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Stama America, 1063 Hawthorne Drive, Itasca, IL 60143, 630-233-8101, Fax: 630-773-1660, www.stama-america.com.