Stama advances the greening of machining

  • 12-Aug-2009 10:44 EDT
Two-spindle machining lowers energy costs by about 40%, four-spindle machining up to 60%.

With Stama’s appropriately named TWIN spindle centers, it is possible to machine two identical workpieces at the same time. The use of energy in that case is on average only 20% higher than with a normal single-spindle machining center, according to the company. The increased consumption is primarily from the second milling spindle. In twin-spindle manufacturing, overall energy consumption per finished workpiece is thereby 40% lower than with single-spindle production.

For workpieces that can be machined on a four-spindle machine, the STAMA-TWIN², the reduction in power consumption is almost 60%.

The created braking energy is fed back to other components of the machine. This is made possible by state-of-the-art electrical drives, the company says. During deceleration, there is a demand for energy from the peripheral units, such as the hydraulic pump, air suction unit, and coolant pumps. The machine’s internal energy-management system uses the gained energy from braking systems and feeds that power directly back to the peripheral units. The machine will not feed back or supply the public network with energy, but will use 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.

Standard on every laptop, new for manufacturing equipment, Stama introduces the multi-step standby mode. In phases, when the machine is not being used for production (for any number of numerous reasons), the peripheral units, as well as the feed axes, can be shut down sequentially. The machining centers are equipped for that scenario with an ECO-Menu. The factory setting for a timely stepped shutdown can be modified to the user’s own requirements. With the “ECO-Mode,” a savings potential of up to 80% in power consumption can be achieved, realizing a savings in energy costs up to approx $1800 per year per machining center.

In standby mode, the machine can be activated without any time delay with a single push of the start button. A self-reactivation mode is also integrated. 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 nonproductive hours.

Another energy-saving feature is the design of work zones for dry machining. In wet-machining mode, the required amount of coolant to wash off and remove chips is noticeably smaller. A benefit in two ways is provided. 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.

Compared to electrical energy, pneumatic energy is considerably more expensive. Pneumatic energy consumption at most companies is very often not evaluated, and so 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 shutdown 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-micron 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 shutdown. With the Stama pneumatic-power-safe feature, 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 weekends.

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