Shop Solutions: Blades Boost Bandsaw Productivity
Many metal sawing shops never make the kinds of cuts that Production Job Services Inc. (PJS; Brookfield, WI) considers its bread and butter. But whether it's dissecting ductile-iron engine blocks for material testing purposes, slicing through tubing with hardness of RC 55, or precision cutting stainless steel, nickel-based, and nonferrous alloys up to 36" (914-mm) diam, PJS knows that careful planning before the cut and optimal blade selection makes a world of difference in sawing productivity.
Gladiator bandsaw blades provide long service life and handle a variety of workpiece configurations and materials at PJS.
A family business, PJS is currently run by president Peter Smith; his brother Patrick, senior VP; and VP and secretary Jim Haggith. Early in the company's history, as the steel industry foundered, the Smith brothers' father started a business to serve the foundries by cutting square stock to specific lengths and weights. Today, about 75% of the company's work is for the investment casting industry. For example, PJS processes "white steel"--the scrap material from casting gates and risers--for casting houses to reclaim. The balance of the business is custom bandsawing.
"We're not set up like larger machine shops," says Peter Smith. "PJS is lean, but being small has its benefits. We own our own equipment, and we keep overhead low because our customers supply the steel. Customers typically come to us now with orders for 500 pieces or less. Just-in-time manufacturing rules the day. In this business climate, sawing on-spec, on-time, and on-budget is critical."
PJS packs a lot of machinery into its 15,000 ft2 (1395 m2) facility, including two shears for handling round and square bar stock to 6" (152 mm), shears for 1/2 - 4 1/2" (12.7 - 114-mm) diam round stock, three CNC horizontal and one CNC vertical bandsaw supplied by HE&M Saw (Pryor, OK), two tube cutting machines, and two Wheelabrator shot-blast machines.
Using blades supplied by The L.S. Starrett Co. Inc. (Athol, MA), the bandsaws cut everything from 1/4 to 36" (6.4-mm - 0.9-m) diam material in all shapes and sizes, from solids and tubing to structural angles and specialty items. PJS handles many special applications, including, for example, cutting 20" (520-mm) OD heat-treated 4140 steel tubes with hardness of RC 40 and segmenting nozzle expanders into pie shapes. Work materials range from carbon and alloy steels including 1010, 4140, and 8620 to type 304, 316, 15-5 PH, and 17-4 PH stainless steels.
"Much of our sawing is done for local shops that operate CNC machines," Peter Smith explains. "These shops are making parts for companies such as Harley Davidson. Work like this, for machining applications, requires high precision and squareness down to half a degree in many cases, plus high-quality surface finish."
PJS also cuts sections from casting products such as engine blocks, because the foundries need to test their pours to ensure metallurgical integrity and detect cracks or flaws throughout the cast. "We're a cut-to-order business," Peter Smith notes. "We're used to delivering results very quickly--typically overnight, sometimes the same day. Cut quality and consistency are critical to us. Cost is important too. Blades are not inexpensive, so extended life is also a key factor."
When PJS recently took on a large cut-off job, the Smiths knew they were in for a fight. But they also knew that as long as they proceeded with caution and used the right blade, they could deliver the goods and profit.
A large local foundry wanted PJS to saw 6' (1.8-m) long sections of 16" (406-mm) diam solid grey ductile iron into 4 1/2' (1.37-m) pieces so they could be used at the beginning of a forging operation. Cut-to-length tolerance was 0.020" (0.5 mm), so there was little room for error.
"We were only given ten days to complete the job, so a good strategy was needed," says Peter Smith. "We reviewed the problem. Whenever we prepare for cuts, we talk about a number of issues. What blade will work best? What pitch will be required? How many cuts can we expect from each blade? How long will each cut take? Are there any issues unique to this type of material? Is it a specialty or repeat job?"
The job presented several challenges. Grey iron is a hard material that produces an exceptionally fine or dusty chip, so penetration and coolant were big issues. PJS considered using carbide-tipped blades--known for their durability, but much more expensive than conventional bimetal blades. "Even with carbide, we estimated that each cut would probably take 35 - 45 minutes, and it would require two to three blades to complete the job," Peter Smith recalls.
"Ultimately, we took a little gamble based on a recommendation from Starrett's factory technical representative," he continues. "He helped us select a 27' [8.2-m] long, 2" [51-mm] wide Gladiator blade with 1 - 2 teeth per inch. And it worked out very well--way beyond our expectations."
According to Smith, the 1 - 2 pitch, in addition to applying minimal coolant on the back side of (after) the cut, prevented gumming or packing of chips in the teeth gullets. The blade yielded 73 pieces-- 14,670 in.2 (94,645 cm2) in just three days. "The average cut time per piece was 15 minutes, under a third of our original estimate with carbide-tipped blades. The finish of the face was outstanding and consistent throughout each cut, plus, we only used one blade and there was still plenty of life left in it," he reports.
Gladiator bandsaw blades feature bimetal construction with fatigue-resistant alloy steel backing for wear and heat resistance. Teeth are triple-tempered M42 HSS with 8% cobalt, hardened to RC 67 - 69 and set at up to a 12º positive rake angle.
According to Peter Smith, the blades perform well on stainless, grey iron, and other alloys. He claims they help PJS improve efficiency, quality, and customer satisfaction. "Gladiator greatly improves our cutting speeds," he says. "It penetrates easily, clears chips quickly, improves surface finishes, and cuts straight and true. And, its variable-pitch tooth design produces less vibration and noise. This is important in our relatively small plant where sound gets amplified. Less noise relieves operator fatigue over the course of a day."
Coolant Keeps People Healthy, Machines Humming
"Skin irritation is so hard to avoid that it often becomes part of the job," says David Lamb, machining manager at Norgren Automotive (Mt. Clemens, MI). "But when it gets to be more than a nuisance, you have to find a better way.
Introducing a mineral-oil-based emulsion coolant eliminated long-standing operator health problems and improved productivity at Norgren Automotive.
"Employee health is the top priority, of course, but there are also costs: health care, substitutions, overtime, lost production, and so forth," he continues. "And, recurring health issues can be disruptive. In a large plant like ours, where much of the production is scheduled around just-in-time deliveries, reliable workflow is essential."
Norgren's Mt. Clemens plant is a large captive machine shop that produces grippers, valves, fittings, pneumatic cylinders, and other components used in assembly lines for automotive and other applications. The plant operates more than 40 CNC and manual machines, and operators had been bothered by health issues for years.
The plant also had trouble keeping machine sumps stable. In many instances, coolant tended to go rancid and become smelly within a few weeks. Daily top-offs were rarely sufficient to keep fluids fresh, and most machines required frequent changes. Coolant consumption was significant.
Norgren had tried a variety of types and brands of coolants before hitting on one that changed things for the better. The new fluid was Blasocut 2000 Universal from Blaser Swisslube Inc. (Goshen, NY). The mineral-oil-based, water-miscible concentrate requires no biocides or biocide additions, derives its lubricity from active, polar ingredients fortified with chlorinated paraffin, is designed for use with most materials and operations, and can be mixed to concentrations up to 25%.
After testing favorably on a turning center, the coolant was gradually introduced on more machines. A Blaser fluid specialist supervised the shop conversion.
Lamb reports that operator health issues quickly cleared up, and, during several years of subsequent use on virtually all machines, no medical side-effects of any kind surfaced. "It's been quite a change," he says. "We are no longer concerned about exposure to the coolant."
At Norgren, the employee health experience has correlated well with reduced fluid maintenance and consumption as well as better machine performance and productivity.
"A clean work environment contributes to reduced risk of health problems, and we achieve it more easily now," Lamb says. "The gummy residue that used to clog up sensors and make surfaces sticky was time-consuming to wash off. The Blaser coolant leaves a thin film of oil, which makes it easy to quickly hose down the inside of the machines and wipe the outside clean."
According to Lamb, some machines in the plant have been running for nearly two years without being recharged. "Only the tools with enclosed fluid systems, or those that have long periods of idle time, are changed more frequently--every nine months," he says. "The larger machines are equipped with stand-alone coalescers to remove tramp oil. But other than that, the concentration adjustments keep the sumps fresh."
Machining operations also improved, Lamb reports. "In one case, we eliminated secondary grinding by milling a 32-µin. microfinish," he recalls. The part is made of 4140 stainless steel, heat treated to Rc 28.
"On balance, tool life and cycle times have improved by 15 - 20%, but the most valuable change has been in the area of improved operator health and reduced medical costs," Lamb concludes. "We don't have skin problems any more, or the various costs associated with them."
Forming Process Makes Climbing Gear
For rock climbers, good equipment can mean the difference between life and death. One of the most used and most important pieces of climbing hardware is the belay/rappel cinch device, so when engineers at The Trango Co. (Boulder, CO) needed a precise assembly method for the company's new belay/rappel cinch they searched for the most reliable assembly method they could find. The patented cinch consists of three main parts--a black nylon handle, a 7075 aluminum alloy base, and a lever produced from investment-cast 400-series stainless steel. Trango's lead design engineer, Seth Murray, analyzed several potential assembly methods before choosing an orbital forming process and equipment supplied by Orbitform Group LLC (Jackson, MI).
The forming solution resulted in a solid stainless steel rivet to hold the locking hardware with a conical peen, along with rolling a hollow form over washers with an altered eyelet peen. A 7075 aluminum alloy pin secures the handle to the base, and the cast lever is joined to the base with a 5/8" (16-mm) diam hollow joint. The tubular end is flared over by the orbital forming tool to capture the part securely. All operations are performed on the same Orbitform B500 orbital riveting machine.
"I chose orbital riveting because it makes a very secure joint," Murray says. "The orbital process allows a large amount of material to be displaced without cracking compared to other riveting methods we have tried."
According to Murray, use of the orbital forming process has resulted in production of high-quality joints with lower scrap rates and increased production.
This article was first published in the July 2005 edition of Manufacturing Engineering magazine.