Machining with less energy

By: Gerald Scheffels

Even if the proportion of energy costs in metalworking companies is lower than in other industries, the increases are not only noticeable, they also change the cost structure. In view of the highly competitive pressure – after all, there are around 20,000 machining companies in the German industrial landscape alone – energy is becoming a factor that can make all the difference: Those who produce in an energy-saving manner reduce component costs and overheads and thus secure a competitive advantage. This is more important as energy costs are set to rise further.

The double benefit of saving energy

But it is not just the costs alone that speak in favor of using energy-saving machine tools. The EU-wide CSRD reporting obligation requires the recording of CO2 emissions at company level, and many metalworking companies, especially the automotive suppliers among them, have already been asked to disclose the CO2 footprint of their products. Those who produce in an energy-saving manner can manufacture components with a small footprint and thus help customers achieve their sustainability goals. Saving energy therefore creates a "win-win situation" for both the economy and ecology.

Machine tools are becoming "greener" and smarter

Where can metalworking companies start in order to produce more efficiently, cost-effectively and sustainably? Firstly, with the machinery. As a rule of thumb, a new machine (tool) consumes around 30 percent less energy than an old one.

These savings are achieved through a large number of individual measures. A few examples: Electric motors in efficiency class IE3, which consume around 60 percent less electricity than IE2 motors, are now standard. Control technology plays a major role. Okuma's "Green Smart Machines" automatically switch peripheral devices such as chip conveyors to idle mode as soon as they are not needed. And Yamazaki Mazak's NEO series CNC control offers functions such as the "Smooth Energy Saver" and the "Smooth Coolant System", which monitor energy consumption and automatically adjust the coolant supply.

These examples already highlight one principle: Saving energy does not come at the expense of precision and productivity. It therefore offers no disadvantages. Additional purchase costs are quickly offset by savings during operation. That is why such machines are in demand. Marco Casanova, Managing Director of Yamazaki Mazak Deutschland GmbH: "The demand for environmentally friendly technologies is constantly growing. We see huge potential in the further development of intelligent energy management systems."

Detailed work on spindles: Reduction in compressed air consumption

Spindle units are among the largest energy consumers in machine tools. The design focuses on performance and cost-effectiveness, but sustainability and energy efficiency are becoming increasingly important. One example: The motor spindle manufacturer Weiss has succeeded in reducing the consumption of compressed air, which is required as sealing air for interfaces, among other things. This is achieved using special labyrinth seals and special throttle valves. Bernd Lang, Head of Sales and Service at Weiss Spindeltechnologie GmbH: "Compressed air is also usually used for oil-air lubrication units. As an alternative, we offer lifetime-lubricated hybrid bearings that are operated with high-speed greases. This completely eliminates the need for transport air for lubrication."

There are also "adjusting screws" for reducing energy consumption at the machine (and spindle) component level – for example in roller bearings. At EMO, NSK will be exhibiting roller bearings with reduced internal friction, thus increasing the efficiency of electric drives in machine tools. In the best-case scenario, a smaller motor can even be selected by using such bearings.

Also not to be forgotten: The secondary processes 

Energy can be saved not only during the machining process itself. The secondary and subsequent processes require at least as much attention – for example parts cleaning, which is strongly represented at EMO. There is great potential here in the temperature control of cleaning baths and the use of demand- and speed-controlled pumps. The cooling of machine tools also deserves attention. Older systems are often oversized and were planned without taking energy consumption into account. New installations therefore have a good chance of rapid amortisation. The same applies to compressed air, which is not without good reason considered an expensive energy source, but offers great potential for increasing efficiency. 

In concrete terms: How to halve energy consumption

The pump manufacturer Knoll provides a specific example. In the engine plant of a German car manufacturer, the pumps in the cooling lubricant supply system of 49 machining centers were replaced. Particularly energy-efficient high-pressure pumps that can be regulated according to demand are now being used. The result: Depending on the machine, the pumps consume between 34 and 69 percent less energy. On average, a reduction of 54 percent was measured, resulting in energy cost savings of around 100,000 euros per year: a great success for a manageable optimisation measure. 

Practical examples: Investing and saving energy

In most cases, energy savings will not be the primary reason for investing in new machining centers. But the effects are considerable and if the machining companies take advantage of subsidy and incentive programs, they are not only relieved financially, but also know the concrete savings effect because they have to prove it. Here are two examples: 

Jost Metallverarbeitung GmbH in Bischoffen, Hesse, has "lightened" its annual CO₂ footprint by more than 240 tons with the purchase of a new Hedelius machining center. 

After investing in a Grob machining center with automated workpiece feed, tool and mold maker Scheld in Gladenbach was able to reduce energy consumption by more than 50 percent compared to the old machine and cut CO₂ emissions by 93 tons per year.