Makino and Sandvik Coromat Advance Cutting Solutions for CGI
MASON, OH-September 2006-Makino and Sandvik Coromant have developed new and innovative solutions and technology for cutting CGI. After extensive tests, the two companies have developed a revolutionary process and tooling that allows CGI cylinders to be finished at near traditional cast iron process times.
David Woodruff, the Makino process development engineer responsible for CGI research, in Mason, Ohio, says, "this new process will allow CGI to be used on an assembled automotive engine, which will make it nine percent lighter than comparative materials and processes. The engine block weight alone can be reduced in weight by 22 percent. This corresponds to a 15 percent reduction in length and a five percent reduction in height and width.
"The nodularity and tensile strength of CGI also increases as wall-section decreases. These properties have most recently been found to make CGI ideally suited for engine manufacturing, where lighter and stronger materials are needed which can absorb more power, provided the right machinery, tooling and processes are used."
Visit Booth # 8301 in Hall A of the South Building during the 2006 International Manufacturing Technology Show (IMTS) at McCormick Place in Chicago, Illinois, September 6 through 13 to learn more about this technological innovation in Compacted Graphite Iron manufacturing.
CGI History
In 1949 a now well-known material called ductile iron was patented. At the same time, a lesser-known material called Compacted Graphite Iron (CGI) was also patented, though it was just considered a curiosity at the time. While ductile iron became a manufacturing staple, CGI never was seriously utilized despite possessing some very interesting properties.
While not quite as strong as ductile iron, CGI is 75 percent stronger and up to 75 percent stiffer than gray iron. The thermal and damping characteristics of CGI are mid-way between ductile and gray iron. It is five times more fatigue resistant than aluminum at elevated temperatures, and twice as resistant to metal fatigue as gray iron.
All V-engines share a common design weakness, as there is a lot of flexing in the V-area between the cylinders when it is under power. CGI strengthens this physical area considerably. Flywheel and clutch components are also made from CGI, as are the disc brakes for high-speed rail trains in Europe to eliminate severe heat-checking and cracks.
Theoretically a CGI engine block can be fabricated lighter than an aluminum block for equal power densities. Class 8 diesel truck engines are about six times heavier than equal displacement gasoline engines, so the potential for total weight reduction is even greater.
New Process Foundation
The key to this new Makino and Sandvik Coromat process is threefold. "The first is an investment in technology in order to change the entire support operation processing methods," says Woodruff. "Makino developed such new processes using advanced machinery like the Makino a81M used in these tests, which is ideally suited to CGI because these platforms have been engineered to higher limits for heavy cutting operations like CGI."
The second step is an investment in simple, special carbide tooling from Sandvik Coromat. Wayne Mason, automotive engine senior specialist for Sandvik Coromant, says, "the revolutionary Long Edge Tool, which is an engineered solution utilizing serration technology, is ideal for finished mill cylinder boring of CGI. This is due to its ability to produce a complete length of bore in one pass. CBN, ceramic and other special tooling cannot be used on CGI due to the material's microstructure and lack of sulphur."
The third factor is utilization of a new process jointly developed by Makino and Sandvik Coromant. This new, tested and proven process is based in part on Makino's patented Flush-Fine machining process, in combination with the machine and tooling technology that allows for the elimination of the semi-finishing boring operation.
The elimination of this semi-finishing step is a substantial reason for the saving of time and enhanced competitiveness of this process in reducing CGI cutting time. Additionally all special tooling, machine and support costs for this operation are eliminated.
The combined quality of the machine and cutting tool provides for this improvement, and allows for operations to proceed smoothly from the rough cuts straight to the finish honing operation. While developing this enhanced process, it was also determined that the roughing process is better attacked by traditional methods. Using inserts and a single-headed tool have proven more effective. Rough boring will be accomplished with a modified milling cutter with newly designed inserts with coatings and geometry optimized for boring CGI.
Previous Machining Solutions
Prior to 2006, there were no real high-speed machining solutions for CGI. It is best considered the titanium of the ferrous world. It is very speed sensitive, and if that speed limit is exceeded, the tool life will decrease quickly and drastically.
Tools and processes thus had to be designed to deal with the disposal of extra graphite, and to gain speed. CGI has been known to hone and grind very well. However, due to its microstructure, CGI has considerably more graphite content in the cutting swarf. Because of the reduced cutting speed with CGI, it can take nearly three times as long as similar cast iron with conventional processes.
Tool life for milling and drilling is less affected by CGI material attributes than cylinder boring or any continuous operations. If milling cutters are selected that are of positive geometry and the right diameter to take advantage of the spindle power curves, then the increase in forces is less of a problem.
Drills are being developed with cutting geometries and special coatings that are designed specifically for CGI to reduce tool wear and enhance cutting forces. One such company is Titex, a subsidiary of Sandvik.
Engine block cylinder boring and finishing efforts are challenges regarding tool life versus cycle times. The high insert density and feedrates also raise the thrust requirements. As with milling processes, if all the aspects are optimized then the cutting force penalties are not as severe.
Continued research and test data constantly being proven out by Makino and Sandvik Coromant will have a tremendous impact on the CGI machining marketplace for years to come. Since CGI rough machines very well, there is the potential with grinding utilization to eliminate some other semifinishing operations.
As an example, Makino is developing proprietary grinding processes and tooling to take advantage of this aspect. There is some promise for ceramic use in this area, but no viable production solutions exist at this time.
Plan to visit Makino Booth # D-4110 in the EDM Pavilion at IMTS to see demonstration on equipment and processes that meet the demand for micro-dimensions and ultra-high precision EDMing.
Makino is a global provider of advanced machining technology and application support, where new thinking takes shape for the metalcutting and die/mold industries. Makino manufacturing and service centers are located in the United States, Japan, Germany, Singapore, Italy, France, Korea, Taiwan, Turkey, China, Mexico, Brazil and India, and are supported by a worldwide distributor network. For more information call 1.800.552.3288, or visit www.makino.com.
Media Contacts
Donald A. Mounce, APR
Brandon Rhoten
HSR Business to Business
makino@hsr.com
513.671.3811
