During the early summer 2010, I needed a lengthy talk with Dale Hill, applications engineer at Greenleaf Corp., the cutting tool manufacturer in Saegertown, Pennsylvania.
Greenleaf design engineers say they combined a higher shear cutting geometry with good edge strength at the purpose of cut to create the Excelerator ballnose milling inserts.
In early summer 2010, I needed a lengthy talk to Dale Hill, applications engineer at Greenleaf Corp., the cutting tool manufacturer in Saegertown, Pennsylvania. Greenleaf carries a tightly focused yet innovative product line but doesn’t do a great deal of splashy promotions to attract attention beyond its target markets. I found myself enthusiastic about the company’s new brand of carbide end mills for the reason that product descriptions hinted at some revealing insights in the nature of insert cutting action. The fact that the line includes both ceramic (WG-600 grade) and carbide (G-925 grade) inserts for the very same cutter bodies intrigued me. Statements in regards to the insert geometry preventing excess “tool pressure” also got my attention.
The discussion with Mr. Hill proved to be enlightening. It is essential he clarified was your relationship between chip thinning, cutting speed as well as heat transfer. This relationship forms the theoretical basis for the strength of the Excelerator end mills, he says. Here is my understanding of the true secret concepts. The bottom line is, the way in which an insert results in a chip determines how the heat generated during metal cutting behaves. Ideally, the cutting action of any insert will create enough heat to market efficient plasticizing of your workpiece material. Plasticizing implies that the fabric becomes soft enough to get displaced inside the form of a chip.
However, exactly the same cutting action must allow the majority of the heat to become absorbed from the chip and carried from the workpiece before affecting the properties in the workpiece material. “For the Excelerator, we put together an insert geometry that can cause a chip having a cross section that is thicker toward the OD from the carbide corner radius end mill and thinner toward the center of the tip,” Mr. Hill explained. This, he says, implies that the thicker portion of the chip carries off proportionately more heat compared to thinner part. This effect is desirable as the relative cutting speed is lower at the centre of the tip. Extra heat put aside through the thinner chip at that point assists with plasticizing the information to make up for lower cutting speed. Meanwhile, the thicker portion of the chip prevents excessive and potentially damaging heat build-up which may occur with the outer portion of the cutting edge. “The chip acts just like a variable heat sink, carrying from the heat in which you don’t want to buy and leaving it where you do,” Mr. Hill explained.
The real key, he explained, is usually to balance this just right to ensure the optimum conditions are created evenly over the entire really advanced. One result is the fact that tool pressure (an item of cutting speed and chip load) is evenly distributed. Put simply, the chip is thinner where the speed is slower and thicker the location where the speed is higher, nevertheless the cutting forces are exactly the same at any time.
“We experimented with cutter geometry until we had derived the actual profile we needed for this to take place. Then we could program our high-performance, five-axis tool grinders to generate this geometry within the inserts,” Mr. Hill said. This geometry incorporates a complex flank clearance and rake angle combination that varies appropriately from periphery to center. Even tool pressure brings about even tool wear over the entire really advanced, which extends the life of the insert by reducing the likelihood that concentrated wear at one point will cause fracture or some other failure.
What does this indicate for ceramic vs. carbide applications? Mr. Hill answered by pointing out that cutting speeds (sfpm) for today’s ceramic insert materials are usually three to four times higher than speeds for coated carbide. Therefore, ceramic cutting tools have the potential to get much more productive than carbide. However, many tapperedend do not possess machine tools with sufficient spindle speeds and axis travel rates to assist those cutting speeds. And when they did, they might must also use shrink- or press-fit tool holders and properly balance the cutter assemblies.
That is why, Greenleaf is seeing its greatest inroads together with the aluminum end mill in the carbide version, Mr. Hill said. Applications in mild steel, for example, typically visit a 20-percent rise in metal removal rates minimizing insert costs utilizing the carbide inserts, he says. Applications in cobalt-based alloys also benefit. Harder steels and nickel-based alloys will likely see significant improvement with all the carbide end mills, however these applications are candidates for ceramic inserts that permit much higher cutting parameters on suitable machines. Titanium, however, needs to be milled with carbide as this workpiece material is extremely vulnerable to thermal damage and cannot tolerate the heat generated through the speeds and feeds necessary for milling with ceramic inserts.
The cutter bodies for that ballnose inserts are produced from heat-treated alloy steel and can be purchased in standard and extended lengths. Diameters cover anything from 3/8 to 1. inch.