Thursday, November 20, 2014

Understanding the 5 Physical Properties of Workpiece Materials

By Tim Aydt, Product Manager – Milling

Whether you are machining parts from cast irons, low-alloy steels or nickel-based alloys, all such materials exhibit five basic physical properties in varying levels. Those properties are abrasiveness, hardness, thermal conductivity, tendencies toward adhesion/ductility and strain hardening.

The proportions of the individual properties in a given workpiece material largely determine its machinability. Relatively soft low-alloy steel will exhibit strong tendencies to adhesion that can lead to edge buildup on a cutting tool and diffusion wear. On the other hand, poor thermal conductivity of a tough nickel-base alloy can generate extreme cutting temperatures that will cause a tool to deform and fail.

In theory, a material’s specified mix of alloying elements determines the type of cutting tools and cutting parameters that will, in turn, produce predictable and normal wear patterns and help increase productivity. The reality, however, is that cutting tools and parameters indicated for a certain workpiece material may not produce such desired results, and often the reason is variability in material composition.

To better understand how the five properties affect machinability, Seco partnered with steel suppliers and other metalworking-related companies to develop an analysis system that measures workpiece properties. The system charts data from quantitative measurements of the five material properties on a five-pointed grid or pentagram with low values appearing near the center and high values toward its borders. The area enclosed by the data points provides a graphic image of the particular material’s tendencies. Using the pentagram, machinists can better match tool features and cutting parameters to the actual properties of the workpiece.

Several common guidelines have resulted from Seco’s analysis system.

  • Material adhesion tendencies create a need for tough tool substrates with tough coatings, sharp edge radii and high rake angles as well as cutting conditions aimed toward temperature control. This means speeds high enough to carry heat away in the ductile chip. Adhesion tool wear patterns include micro chipping, built-up edge, flaking and notch wear. 
  • Tools aimed at handling material hardness should have strong substrates (depending on the feedrates employed) as well as cutting edges with small rake angles applied at low feedrates and shallower depths of cut. Typical tool wear includes plastic deformation, chipping and breakage.
  • Machining materials that tend to strain harden require tools with toughness and small nose radii and cutting edge geometries for low cutting speeds, high feedrates and deeper depths of cut. Prominent tool failure modes include plastic deformation, chipping and notching.
  • Materials such as superalloys that exhibit poor thermal conductivity mandate the use of tools with high compressive strength, high rake angles and strong cutting edges. Low cutting speeds and feeds are typical. Tools usually fail via plastic deformation or simply from a higher-than-normal wear rate. 
  • Tools intended for abrasive workpiece materials should be engineered with abrasion-resistant substrates and strong cutting edges. Low feedrates and cutting speeds but high depths of cut are appropriate. Wear mechanisms include flank and crater wear and notching.

For more information on how workpiece material properties influence the machining process, please feel free to contact me.

About the Author
Tim manages Seco’s indexable milling product line for Seco NAFTA. In his spare time, he enjoys playing golf and working out.

Monday, November 17, 2014

No Magic Bullet for Global Success Exists

Guest Blogger: Lisa Seidl, Manager of Marketing Communications

Last month, the Society of Manufacturing Engineers (SME) invited me to attend the Detroit Economic Club’s monthly luncheon at the Detroit Marriott. The guest speaker was Mary Barra, CEO General Motors Company. Her topic was Driving Transformation and Economic Growth.

I was quite proud to be in the audience for a couple of reasons: 1) being a female in the manufacturing industry and; 2) working for a Michigan-based manufacturing company. I have not heard many speeches from Mary, other than 5-second snippets on television regarding GM’s recall issues. She is very impressive in the fact that she is so down-to-earth. I came away so energized by her talk, that I wanted to talk more about it!

She explained that her vision for General Motors is to become the global leader in the auto industry; not just ok or second best – The Best! She realizes this will take time, it will not happen overnight and there is still a fair amount of work to do to achieve this. There is no magic wand. It will take dedication and hard work to get through the current recall issues. 

Mary highlighted that to achieve these goals, GM’s culture must shift towards problem solving together, being candid with each other and having a tenacity to win. Global strategies must ensue and she has a true passion for the company. One of several current GM innovations is V to X technology – a system where vehicles talk to one another. This will appear in the next-gen Chevy Volt 2015. GM is striving to be the global leader through electrical vehicle technology. They plan to invest $1.8 billion in engineering and electric technology. A new manufacturing facility will be established in Warren, Michigan to house production of the complete electrical drive system.

Mary went on to give us a look into her personal life. After graduating from Kettering University in Michigan, she went on to Stanford in Silicon Valley for her secondary degree.  She is passionate for Science, Technology, Engineering, Math (STEM) programs. She described how the excitement and awareness for students to get involved with STEM begins with junior-middle school children.

When asked if she could give unconventional advice on what it takes to become a female CEO of a Fortune 100 Company, she responded “do what you love, work hard!” Her role models were her parents. Her Dad retired from GM as a diemaker and her mother was a bookkeeper. They both worked hard to give their children a better life. Mary’s favorite car of all the GM vehicles she has driven is the Cadillac CTS, because of its technology, design and performance.  She does, however, also love the Camaro.

In summary, I was most impressed with the fact that Mary did not have a magic bullet for success. She attributed hard work, collaboration, and passion for what you do every day to succeed. She truly is the epitome of a Woman in Manufacturing; and I could relate.

About the Author
Lisa is the manager of marketing communications for Seco Tools, LLC. She manages North American activities to encompass advertising, trade shows and machine tool builder events, communications and public relations. She and the MarComm team provide sales and distribution support with product launch introductions and promotional collateral. She also works globally with corporate brand identity to ensure the integrity of the Seco brand internally and externally. In her spare time, she likes to golf and cheer on the Detroit Red Wings hockey team.