Thursday, September 25, 2014

Simple Steps to Environmentally Aware Productive Machining

By Todd Miller, Manager of Product Marketing

In a world where energy is a rare, expensive commodity and pollution is a continually growing concern, there’s a growing need to machine components in a more efficient, environmentally responsible, “green” way. 

When machining complex components from high-performance workpiece materials such as nickel-base alloys, ultimate productivity in many cases is not of primary importance. The operations focus more on reliably producing dimensionally and qualitatively perfect parts. That is not to say economic and environmental considerations are irrelevant, but technological productivity and process security challenges are so prominent that efficient, green machining is not the top priority.

The story is somewhat different with simpler parts and more common workpiece materials such as steels and cast irons. Today, steels and cast irons make up the bulk of the materials machined worldwide, and all indicators show a stable situation in the tonnage that will be machined in coming decades. Employed across all industries, steel alloys offer a very good price-performance ratio in terms of cost, strength, and ease of machining.

Wide application and long familiarity have made the purely productivity-oriented aspects of steel machining less crucial. Manufacturers know how steel behaves and are rather sure they can create solutions that will guarantee good productivity.

As a result, our customers who machine steel are increasingly interested in the economical and environmental consequences of their machining operations beyond technological productivity issues.

Research institutes and universities around the world are examining ways to perform machining in a way that puts less load on the environment, namely using less energy and making less waste.

Part of the process involves gaining an overall perspective on the machining process. For example, we have found that workshops do not always realize that energy costs, specifically of electricity, are on the same or even somewhat higher level as cutting edge costs, expressed in cost per minute. Electricity costs include not only operation of a machine’s spindles and axes, but also CNC units and auxiliary equipment such as coolant and workhandling systems. 

There are many ways to reduce the energy consumed in the cutting process itself. Application of certain insert geometries, for example, can contribute to energy conservation. Where use of a sharper geometry is appropriate, 1-degree extra positive rake angle can reduce energy consumption by 1.5 to 2.5 percent.

Manipulating cutting speeds represents another opportunity to save energy. Productivity is the traditional goal in machining, and achieving it has almost always involved employing higher cutting speeds. However, one way to reduce energy consumption is to lower cutting speeds and proportionally increase feed rates and depths of cut.

If a machining application permits working with a combination of lower cutting speeds and higher feed rates and depth of cut, at least three benefits result. One advantage is that less energy is required to remove material from the workpiece. We have found that a one percent reduction of cutting speed reduces energy consumption by five percent; a one percent decrease of depth of cut combined with one percent increase of feed rate reduces energy consumption by two to three percent.  

Another benefit of lower cutting speeds can be longer tool life. Fewer cutting edges or inserts are consumed over a certain amount of time or over a certain number of workpieces. There’s a reason indexable tools have historically been called “throwaway” inserts; at the end of tool life, they end up as waste in the environment. At slower speeds in combination with other cutting parameter adjustments, however, fewer inserts are consumed to do the same amount of work.

A third advantage of the application of lower cutting speeds is a reduction in the heat generated in the metalcutting operation. In addition to contributing to longer tool life, reducing heat also lowers the cooling requirements of the cutting system and less coolant is needed. That is environmentally significant because used coolant is full of metals, lubricants and other contaminants and poses particularly troublesome and expensive disposal problems.

Of course, reducing the environmental impact of metalcutting operations goes far beyond tools and tooling systems. Complementary efforts to improve the environmental status of machining include recycling of chips and used carbide, moves to minimal-coolant or dry machining processes, and even research into use of workpiece materials that themselves require less energy to make. Productivity will always be the ultimate goal in metalcutting and manufacturing overall, but analytical thinking and simple actions can make productivity go hand-in-hand with resolution of environmental concerns.

About the Author
Todd is the manager of product marketing for Seco Tools, LLC. He oversees the product marketing team and works with the company’s sales department to further enhance the customer experience. He and his team also support product introductions while working globally on new product testing to ensure customers gain access to the industry’s most advanced tooling as quickly as possible. In his spare time, Todd likes to bowl and cheer on the University of Michigan football team.

No comments:

Post a Comment