With tapered ramps built into a band saw blade, a shop increases blade life when cutting exotic steels
January 2013 - If you’ve ever worked your way through a metal pipe only to have the hacksaw blade snag, the struggle of regaining a cutting rhythm after you’ve negotiated the blade free is familiar. On the next attack, you slightly angle the saw forward and gradually tilt it back, giving the blade a fresh bite for a complete cut without pinching the pipe. You finish the cut with less work and wipe your brow.
In metal cutting machinery, some band saws achieve this effect by tilting the blade. But, as Houston-based Metal Cutting Specialists found, using a blade rather than a saw to produce a continuous rocking action will cut some of the toughest metals, without wearing teeth, after one job.
MCS, as its name suggests, offers one service at which it excels: cutting metal. The company cuts ferrous and nonferrous steels, titanium, stainless and exotic alloys such as Hastelloy and Inconel. Located near the nexus of the U.S. oil industry, MCS regularly cuts metal for tools used in hydraulic fracturing and shapes that go into offshore oil wells for downhole connectors. During the Deepwater Horizon oil spill in 2010, MCS cut parts for the blowout on an emergency basis.
“We have the largest facility of this kind in the United States, with the largest equipment going up to 82 inches in work thickness capacity cutting blocks up to 40,000 pounds,” says Leonard LaNoue, president at MCS.
To cut the harder exotics, particularly Inconel, MCS uses a triple-chip carbide-tipped band saw blade with SineWave technology, made by Simonds International, Fitchburg, Mass. Simonds is a manufacturer of metalworking saw blades.
Although the blade tip seems like the logical place to optimize cutting, Simonds focused on the back-edge geometry. By grinding a series of tapered ramps on the back at lengths engineered specifically to the sawing application, Simonds designed a blade that naturally rocks into the cut. The ramps create a broaching action that lets the machine exert more cutting force over fewer teeth without increasing feed pressure as the back of the blade runs through the machine guides.
Save on sawing
It’s no secret that Inconel superalloys are among the toughest metals to cut. Their complex grain structure is ideal for the high-temperature applications for which MCS supplies cut metal. For years, MCS has been cutting 20-inch to 30-inch-diameter Inconel 718 and 708, among other hard alloys. Blades didn’t last long.
“We were getting two or three cuts with one blade, so our tool cost was high,” says LaNoue. But the blade life issue went unaddressed, perhaps because MCS cuts superalloys, which can consume high volumes of blades.
When David Rosing, technical manager of band saw products at Simonds, visited MCS on a service call for one of its welders (MCS welds its own band saw blades), he asked MCS which material or cutting application caused them the most blade issues. MCS cuts tough materials and complicated and intricate shapes, which require extensive set up.
“They said 32-inch rounds of Inconel,” Rosing explains. “I said, ‘Let’s try this SineWave blade.’”
MCS installed the blade during Simonds’ next visit. The blade easily made one cut. Then a second. And a third. “Then we got to seven cuts and we basically eliminated any concern about the blade being more expensive,” Rosing says.
The SineWave blade also gives MCS a cleaner cut and reduces the amount of out-of-square compared to other blades because of the difficulty in machining hard material. That can be a problem for cutting large exotics. In addition to oil industry work, MCS cuts structural steel for chemical plants, refineries and some work that goes into aircraft industry.
“Some of these billets weigh about 22,000 pounds when they come in, worth a quarter million dollars,” says LaNoue. “We have to be careful because we don’t want to scrap them.”
Since cutting with the SineWave, MCS reduced its tool costs tremendously. As other operating costs have risen, the SineWave helps MCS keep its costs in line with what it charges for doing a part. After MCS boiled down the numbers, LaNoue says it previously cost $154 per cut. With the SineWave, it’s $51 per cut.
“It definitely helps offset additional labor and other costs that come up,” he says. “We increased our tool life by roughly 700 percent.” Although the blade is a more expensive product, it is justified by the tough material MCS cuts, he adds.
Wave in the works
The SineWave blade’s ramping action is a simple, effective idea. With a regular flat-back band saw blade, the contact area of the blade increases as a cut progresses—on the tips and sides. Deeper penetration requires proportionally downward, heavy pressure to maintain cutting rates. This is the point where blade teeth can fracture or the blade can cut crooked.
With SineWave blade’s tapered ramps, the blade continuously changes the angle of approach as it runs through the guides. This oscillating motion constantly changes the cutting plane, reducing the area of tooth contact, maximizing blade life and expediting cuts. It’s the same effect as tilting a hacksaw every few strokes through the workpiece. Thus, as the blade ramp surges, more force is transferred into metal. For that reason, MCS doesn’t have to adjust feed pressure during a cut.
“At one point, every two feet when the blade comes back, you get an additional point of pressure that causes it to penetrate. It reduces the chance of work hardening that exists with this kind of cutting,” LaNoue adds.
The SineWave technology can be added on all of Simonds’ M42 bi-metal and carbide tipped band saw blades from 1 inch to 31⁄8 inches, according to the company. The blade is designed specifically for challenging aerospace steels like chrome, tool, die, stainless and nickel base, exotic metals and titanium. For MCS, the tooth pattern is a triple chip grind, a design that gives optimal chip penetration and formation.
However, it’s not ideal for softer metals because they don’t require as much pressure to penetrate, says Rosing. For that reason, the tougher the job, the greater the benefit with the SineWave.
“The broaching action of the blade is most effective on difficult-to-cut grades of materials,” he says. “Stainless steel is typically the threshold where one can distinctly benefit with SineWave, with the greatest benefit coming when cutting aerospace alloys.”
Rosing also says, “the larger the workpiece, the greater the SineWave benefit as the tendency to cut crooked increases with material size. This technology greatly reduces or eliminates crooked cutting.”
Although Simonds has offered some form of a ramped blade for decades, it was only about five years ago that the company came up with a customizable CNC version. The ramp length, depth and contour can be specifically engineered, depending on material to be cut. Instead of offering one generic ramp, Simonds offers light, medium and aggressive grinds tailored for different machines and metals.
Generally, the harder the material, the faster the SineWave will cut, compared with a standard blade without ramps. “In some places we see 50 percent, but at a minimum it’s 25 percent faster, so you get more parts on the floor,” Rosing adds. “The only way we measure is by cutting square inches and time, so to be able to cut more area in a shorter period of time is key.”
Rosing says many shops don’t want to switch blades for different metals. They want to cut everything with one blade. “We can optimize the blade geometry to the largest and most difficult material so we can solve that challenge, cut faster and straighter yet still get more cuts per blade.”
The latter scenario makes more sense because it’s worth it to customize the blade and save—especially if a shop like MCS is cutting larger billets regularly.
“People today are becoming more and more resourceful,” says Jim Hopp, Simonds’ territory manager for the Houston area. “That’s why we offer tailor-made blades for each application.”
The fact that MCS can sustain a seven-fold savings by switching to SineWave is testament to Simonds’ customer attention.
“I could see, the years I’ve been involved in this business, they understood what was happening in the shop,” LaNoue says about Simonds’ representatives. “They really helped us because of their knowledge. They spent hours working with us to make sure the blade worked properly, which most salesmen don’t do.” MM
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