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END USER: MSI Corp., (724) 567-6500, www.msicorporation.com. CHALLENGE: Effectively cut a large amount of material on older machines without damaging cutting tools. SOLUTION: A milling cutter tooled with inserts that enable a large DOC at a low horsepower. SOLUTION PROVIDER: Sandvik Coromant Co., (800) SANDVIK, www.sandvik.coromant.com/us
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When removing 0.75 " of material from a 50-ton forged steel workpiece in a single pass, you need a setup that can take serious abuse. Finding the right combination of satisfactory surface finish and profitable production was a challenge for MSI Corp. But a test of a new milling cutter led the company to a simpler and faster machining process when milling heat-treated 4340 alloy steel. When applied throughout the shop, the new cutter allowed MSI to increase productivity by 75 percent through taking on more work. In the process, the cutter got a nickname—“The Bulldozer.”
Vandergrift, Pa.-based MSI is a large, diversified steel and titanium processor. It performs first-stage machining (gauge reduction) and material conditioning (defect removal) on large workpieces for metal producers.
MSI also performs abrasive blasting, abrasive sawing, belt grinding, bar peeling, bandsaw plate and dial column sawing, centerless grinding, CNC turning, deep-hole drilling, heat treating, planer milling, vertical boring and waterjet cutting.
“We are in the middle of the entire process,” said Duke McLaughlin, CEO of MSI. “It’s not uncommon for the material to come to us multiple times for the same process between different production phases.”
Workpiece size and weight—up to 70 ' long and from 8,000 to 125,000 lbs.—make setup difficult. Add the task of cutting difficult-to-machine materials such as titanium, stainless steel, carbon steel and P/M and you have a machining challenge few companies can meet.
With a specialized solution, MSI is up to the task. The company uses older—50 years old in some cases—manual planers built with 100- to 150-hp motors and twin columns capable of managing unwieldy workpieces.
The large planers are effective but can abuse cutting tools. Because of their massive size and power, the mills typically create a great deal of heat when machining. And, with only a few speeds and feeds available on the planers, MSI often facemills at less than ideal conditions.
“We’ve always had difficulty with the forged material we receive from our customers,” McLaughlin said. “The material is forged or rolled oversized in case there are cambers, twists and other manufacturing defects, and we have to remove a huge amount of material—fast!” The hammer-forged parts have divots and gullies from being hammered during the forging process. Extra material containing the defects is left on during forging and MSI removes it to achieve a smooth, workable surface.
Courtesy of Sandvik Coromant
Below, MSI removes 0.75 " of material from a 50-ton forged 4340 alloy steel workpiece in a single pass with the CoroMill 360 milling cutter (above) from Sandvik Coromant.
Needless to say, MSI is always in the market for cutters that can withstand these harsh conditions. When John Dolan, productivity engineer for Sandvik Coromant Co., Fair Lawn, N.J., brought the CoroMill 360 to MSI, McLaughlin agreed to a test cut on heat-treated 4340 alloy steel. “We’re always looking to take bigger cuts, or bites, due to the total amount of material we have to remove,” McLaughlin added. He was impressed with the results.
“We took a 12 "-dia. CoroMill 360 cutter, engaged 10 " of the workpiece and took a ¾ " cut without coolant,” McLaughlin said. “We cut for 2 days at 18 ipm. We were making chips bigger than my thumb.”
After cost-savings analysis and more testing, McLaughlin purchased left- and right-hand CoroMill 360s for every planer in the shop and uses the tools for nearly all of the materials processed by the shop, achieving major cycle time reductions. He noted that his first 360 body, installed in April 2009, is still operating.
In the example of machining 4340 alloy steel, what took five passes and a finish cut can now be done in just two passes: a 0.75 " roughing cut and a 0.25 " finish cut.
The CoroMill 360 accepts 60° inserts, which due to their chip-thinning effect allow for large DOCs and shorter machining times, but at a low horsepower suitable for 45° inserts. The result is a lighter cutting action. The use of a relatively large entry angle also permits the use of wide parallel lands on inserts with minimal compromise on cutting-depth capacity. The lands generate a fine surface finish without a wiper insert. Through optimal distribution of radial and axial cutting forces, the 60° inserts promote stability and lower vibration when entering and exiting the workpiece. The new tool generates less heat than the previous tool and allows MSI to machine dry.
Added McLaughlin, “The CoroMill 360 is cost effective for us because of its ability to hold two insert cassette sizes. We replace 28mm inserts with 19mm inserts for lighter DOCs.”
The new milling solution has also alleviated the risk of tool damage associated with inexperienced operators. “On the first cut, an inexperienced operator sometimes runs the cutter into a piece too fast or too deep and completely destroys the tool,” McLaughlin said.
“With the 360, if the operator goes in too fast or deep, it can take it. It has increased our capacity and simplified operations—all without adding capital equipment,” McLaughlin said.
Related Glossary Terms
- abrasive
abrasive
Substance used for grinding, honing, lapping, superfinishing and polishing. Examples include garnet, emery, corundum, silicon carbide, cubic boron nitride and diamond in various grit sizes.
- bandsaw
bandsaw
Machine that utilizes an endless band, normally with serrated teeth, for cutoff or contour sawing. See saw, sawing machine.
- boring
boring
Enlarging a hole that already has been drilled or cored. Generally, it is an operation of truing the previously drilled hole with a single-point, lathe-type tool. Boring is essentially internal turning, in that usually a single-point cutting tool forms the internal shape. Some tools are available with two cutting edges to balance cutting forces.
- centerless grinding
centerless grinding
Grinding operation in which the workpiece rests on a knife-edge support, rotates through contact with a regulating or feed wheel and is ground by a grinding wheel. This method allows grinding long, thin parts without steady rests; also lessens taper problems. Opposite of cylindrical grinding. See cylindrical grinding; grinding.
- computer numerical control ( CNC)
computer numerical control ( CNC)
Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.
- coolant
coolant
Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.
- finish cut
finish cut
Final cut made on a workpiece to generate final dimensions or specified finish. Often made using reduced feeds and higher speeds. Generally, the better the surface finish required, the longer the finish cut takes. Also, the final cut taken on an electrical-discharge-machined part.
- gang cutting ( milling)
gang cutting ( milling)
Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.
- grinding
grinding
Machining operation in which material is removed from the workpiece by a powered abrasive wheel, stone, belt, paste, sheet, compound, slurry, etc. Takes various forms: surface grinding (creates flat and/or squared surfaces); cylindrical grinding (for external cylindrical and tapered shapes, fillets, undercuts, etc.); centerless grinding; chamfering; thread and form grinding; tool and cutter grinding; offhand grinding; lapping and polishing (grinding with extremely fine grits to create ultrasmooth surfaces); honing; and disc grinding.
- inches per minute ( ipm)
inches per minute ( ipm)
Value that refers to how far the workpiece or cutter advances linearly in 1 minute, defined as: ipm = ipt 5 number of effective teeth 5 rpm. Also known as the table feed or machine feed.
- milling
milling
Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.
- milling cutter
milling cutter
Loosely, any milling tool. Horizontal cutters take the form of plain milling cutters, plain spiral-tooth cutters, helical cutters, side-milling cutters, staggered-tooth side-milling cutters, facemilling cutters, angular cutters, double-angle cutters, convex and concave form-milling cutters, straddle-sprocket cutters, spur-gear cutters, corner-rounding cutters and slitting saws. Vertical cutters use shank-mounted cutting tools, including endmills, T-slot cutters, Woodruff keyseat cutters and dovetail cutters; these may also be used on horizontal mills. See milling.
- parallel
parallel
Strip or block of precision-ground stock used to elevate a workpiece, while keeping it parallel to the worktable, to prevent cutter/table contact.
- planing machine ( planer)
planing machine ( planer)
Machines flat surfaces. Planers take a variety of forms: double-housing, open-side, convertible and adjustable open-side, double-cut and milling. Large multihead (milling, boring, drilling, etc.) planers and planer-type milling machines handle most planing work.
- sawing
sawing
Machining operation in which a powered machine, usually equipped with a blade having milled or ground teeth, is used to part material (cutoff) or give it a new shape (contour bandsawing, band machining). Four basic types of sawing operations are: hacksawing (power or manual operation in which the blade moves back and forth through the work, cutting on one of the strokes); cold or circular sawing (a rotating, circular, toothed blade parts the material much as a workshop table saw or radial-arm saw cuts wood); bandsawing (a flexible, toothed blade rides on wheels under tension and is guided through the work); and abrasive sawing (abrasive points attached to a fiber or metal backing part stock, could be considered a grinding operation).
- turning
turning
Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.
- waterjet cutting
waterjet cutting
Fine, high-pressure (up to 50,000 psi or greater), high-velocity jet of water directed by a small nozzle to cut material. Velocity of the stream can exceed twice the speed of sound. Nozzle opening ranges from between 0.004" to 0.016" (0.l0mm to 0.41mm), producing a very narrow kerf. See AWJ, abrasive waterjet.
- wiper
wiper
Metal-removing edge on the face of a cutter that travels in a plane perpendicular to the axis. It is the edge that sweeps the machined surface. The flat should be as wide as the feed per revolution of the cutter. This allows any given insert to wipe the entire workpiece surface and impart a fine surface finish at a high feed rate.
