CASE HISTORY: TOOLS & SUPPLIES

Cutting the costs of cutting aluminum and abrasive materials

Manitoba foundry boosts bandsaw productivity 25% to 100%; cuts blade cost six-fold, by trading carbon sawblades for carbide.

An exclusive Online Feature from the editors of mro-esource.com

© 2000 Machinery & Equipment MRO (1100 words)

For a hard-working aluminum foundry, switching from carbon steel bandsaw blades to a strong-set carbide blade paid off in blade life and bandsaw productivity. Custom Castings Ltd. of Winnipeg, Manitoba, Canada, found a that one single blade from Bahco Tools, Inc. (formerly Sandvik Saws & Tools Co.) outlasted 40 carbon steel blades. It also produced parts 25% to 100% faster.

The same carbide-tipped blade proved tough enough to contour-cut a heavy cast-iron mold and save a week or more otherwise lost in outside water-jet cutting. The machining department supervisor observes, “This blade is far ahead of anything we’ve used before. The time and cost savings are really impressive.”

Custom Castings is a permanent-mold foundry. It produces a broad range of aluminum parts from tractor steps and oil field components to explosion-proof electronic enclosures. The castings range in size from 1 lb to 50 lb, including gates and runners, and most are separated or trimmed on three bandsaws.

Nearly all the parts made by Custom Castings are 356.1, 356.2 or 319 aluminum alloys that are relatively easy to cut but tough on carbon steel bandsaw blades. The high sawing speeds possible with free-cutting aluminum in thick castings generate lots of heat.

Aluminum castings can also have hard inclusions. According to The machining department supervisor, “Aluminum’s not always as soft as it seems.” Bandsaw blade life naturally varies with the parts cut, but the foundry found each bandsaw typically used 10 carbon steel blades a month.

Longer life

Bi-metallic bandsaw blades with hardened steel teeth typically last a few times longer than carbon steel blades when cutting aluminum. However a modest improvement in blade life makes it difficult to justify bimetal with a price typically four times greater than carbon steel. By comparison, carbide-tipped blades are several times more costly than bimetal, but they can justify themselves with dramatically longer life and far higher cutting speeds.

Information from a Bahco technical expert led the machining department supervisor to investigate the 3869 Carbide Triple Set carbide blade. Custom Castings then installed the blade on a 5-hp Grobe 4V-24 bandsaw. Four months later, the test blade was still cutting and after 70,000 castings showed almost no tooth wear.

The Custom Castings machining department supervisor observes, “Some carbon blades last two days and others go a week. This carbide blade has lasted four months. Our carbon blades last anywhere from 200 to 5,000 parts. The carbide blade cut 25,000 castings in the first month and it was still cutting.”

The savings in blade replacement costs are striking. Custom Castings typically pays C$30 (US$21) each for carbon steel blades and consumes 10 blades a month per machine. After four months, the C$200 (US$140) carbide blade has outlived C$1,200 (US$840) in carbon blades, a six-fold savings.

Faster cuts

The carbide-tipped blade has also improved productivity with far faster cutting. Custom Castings runs carbon steel blades around 700 sfm. By comparison, the carbide-tipped blade cuts at 1,200 to 1,300 sfm. In one typical job, the output of cast tractor steps increased from 20 parts an hour with carbon steel blades to 30 parts an hour with the carbide sawblade, a 50% improvement. Each step is about 1 ft wide by 2 ft long by 10 in. high, and the smooth finish left by the fast-cutting carbide blade saves finishing time.

The machining department supervisor explains, "With the carbide blade, we can jam the parts through the saw as fast as we want. We get a nice straight cut that makes things easier for the sanding department."

Big job

The tough, fast-cutting carbide blade also enabled Custom Castings to cut a 1,400-lb ductile iron mold, a job that would otherwise have required costly outside water cutting. The 45x14x12-in. mold was designed to cast aluminum forklift arms but required three wavy contour cuts through its length to facilitate handling and cooling. Similar jobs were previously shipped to Toronto for water cutting, but the water cutter quoted C$3,000 for the big mold. Turnaround time for the piece would have been at least a week.

The Custom Castings saw shop tackled the job with the new carbide blade. "A carbon steel blade would have taken forever and a day to cut that block," says the machining department supervisor. "The carbide blade is very aggressive. We set the mold on ball bearings, wrapped a chain around it, and cut the block on the bandsaw in nine hours. We saved about $2,000." Total machining time, including setup, was 12 hours.  

Cast ductile iron impregnated with silicon and other impurities is twice as abrasive as aluminum, and the bandsaw blade encountered hard inclusions twice during the sawing job. "When the carbide blade hit the hard spots, the sparks started flying and the blade started ticking. After about an hour, the ticking went away, and the blade still cut great. With a carbon blade, if you hit a hard spot, the blade is immediately ruined."

Wavy contour cuts also put high stresses on unset bandsaw blades. The strong triple-set tooth pattern of the 3869 blade makes a wide kerf and is more forgiving of turning stresses. The strong set actually helps steer the blade through turning cuts. After four months of heavy duty cutting, the strong-set carbide blade remained on the job. According to the Custom Castings machining department supervisor, "This is a great cutting blade, and we're getting the most out of it.”

Bahco Tools, Inc. (Scranton, PA), is the US-based part of the Bahco Group, which is part of Snap-On, Inc. Bahco Tools, Inc. is the new name for the former Sandvik Saws and Tools Company, which Snap-On acquired in 1999.

This report was edited exclusively for mro-esource.com Online Features. Placed online June 1, 2000. For further information, contact Bahco Tools, Inc. at  (800) 828-9893 or visit www.sandvik.com or www.snapon.com. © mro-esource.com and Machinery & Equipment MRO magazine, Toronto, Canada. Not reproducible in any form without written permission of the publisher. Contact: broebuck@businessinformationgroup.ca.

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