New breed of facemills offer versatility

Lightweighting has become more popular in automotive and aerospace for increasing fuel efficiencies. As a result, manufacturers need faster, more efficient facemilling techniques to handle difficult-to-machine materials, such as high-silicon aluminum and other abrasive materials. Speeding up machining processes is always critical. Many of the newer facemills can perform both roughing and finishing operations, extend tool life and boost productivity to help shops lower costs.

Some of the newest facemills are PCD or polycrystalline cubic boron nitride (PCBN) tools, which are typically used for machining the most abrasive materials, particularly in automotive engine applications for machining critical surfaces that require real flatness. These facemills also target bimetal machining, such as gray cast-iron cylinder sleeves in aluminum engine blocks.

Facemills that can rough and finish are highly advantageous in a shop. “Not very often do you see customers wanting to have roughing facemills and then a finishing facemill,” said Tim Aydt, product manager of indexable milling at Troy, Michigan-based Seco Tools LLC. “It’s all dependent on the finish requirements and on machine capabilities. We try to look at everything and establish the best possible outcome for the customer.”

Sandvik Coromant’s new M610 bimetal cutter targets automotive engine applications for finishing aluminum blocks with gray cast-iron sleeves. Image courtesy of Sandvik Coromant

If a customer’s machining carousel is crowded, then “chances are that facemilling is going to be a combined operation,” he added. “It’s going to take the material off the top to rough it and clean it off, and it’s probably going to act as a finishing cutter as well.”

Many traditional facemills feature lead angles that range from 45° to 68° and are often for roughing and finishing, Aydt said, noting that facemilling is generally the first operation performed on a part. Seco recently announced its Double Quattromill 22 facemill, which allows users to take a large DOC while offering freer cutting than the company’s earlier Double Octomill facemills.

“This version of facemill is something we haven’t had, in that it offers a very large depth-of-cut capability,” Aydt said. “To take advantage of that capability, you need a fairly large machine with significant torque and horsepower in order to use that tool to its full advantage. The Double Octomill, with 16 cutting edges, is more economical. While the Double Quattromill 22 offers eight cutting edges, it’s much freer cutting. That’s an advantage with certain high-tech materials.”

The new cutters come in three insert ranges with different edges and grade options. The most common, the ME12 geometry, is effective for cutting stainless steel and superalloys, with edge protection and positive rake, Aydt said. The M12 geometry comes in many grades for compatibility with most workpiece materials, and the M18 cuts steel and cast iron that require heavier edge protection.

Combo Cutters

With automotive applications that require machining aluminum blocks and cylinders with cast-iron sleeves, facemills typically are the first step in the machining process, said Joe DeRoss, milling specialist for Sandvik Coromant Co., Fair Lawn, New Jersey.

“The part is either cast or it comes in as a raw material (bar stock), so you have to machine it to near net shape or net shape to get started,” DeRoss said. “Facemills today are so versatile you can also finish by changing inserts.” He added that switching to the finishing insert is easy with a Coro-mill close-pitch cutter, which has up to 12 cutting edges per insert.

“You can get what we call close pitch, which lets you remove a lot of material faster with better finishes,” he said. Choosing a cutter pitch depends on the workpiece material, the required surface quality, the machine’s horsepower and the stability of a setup.

The more inserts applied, the more draw on horsepower, he added, which is a big factor to consider. The close-pitch cutters result in short chips.

“Aerospace and automotive are the highest users,” DeRoss said. “Especially in automotive, there’s a lot of cast-iron materials, so you can get away with close-pitch cutters.”

Sandvik Coromant’s facemill lineup includes dozens of cutters with varying geometries, pitches and lead angles, he said, including coarse pitch, medium pitch and central lead angles.

Among the latest offerings is the M610 bimetal cutter targeted at automotive engine applications for machining gray cast-iron blocks with aluminum cylinder sleeves. Another, the M5B90, is aimed at all-aluminum applications.