Shop Solutions: Five-Axis Fits Company's Philosophy
Engineered Components Corporation (ECC; Providence, RI) is a contract manufacturer specializing in high-quality, complex precision parts that lend themselves to use of five-axis machining technology. President Andrew Rosenholm is a second-generation owner in the precision tool and die business. Like his father, Andy has developed a service-oriented business by exploring and implementing new technologies to gain a competitive edge.
ECC's diverse customer base spans the medical, aerospace, automotive, and consumer industries. The company had been successful using four-axis machining to produce tight-tolerance parts with complex, 3-D geometries. But a challenge from a major customer drove the company's quest for a new solution.
"We were producing acceptable parts for this customer with a traditional four-axis machine," explains Rosenholm. "The parts worked fine, but as the customer's requirements became more strict, we were unable to meet their needs with traditional machining processes. The part design was highly complex, with tolerances of ±0.0001" [2.5 µm], and the material was stainless steel. It became obvious we had to do something different."
Rosenholm began his search for a machining solution based on a fundamental need to machine small precision parts with great speed and exceptionally high accuracy. He investigated all available machines on the market, but chose the HSM 400U five-axis machining center from Mikron Corp. (Lincolnshire, IL). "Mikron machines are purpose-built to be five-axis machines," Rosenholm explains. "They were the most well-integrated machining centers we encountered."
Other factors also contributed to the choice. "The machine seemed perfectly suited for us," says Rosenholm, who saw the HSM 400U in action at Mikron's High Speed Machining (HSM) Competence Center in Milford, MA. "But the manufacturer's service and support was also a very important consideration. We could have, perhaps, bought a great machine out of Germany, but there may be only two in the United States. That would not do us any good and we did not want to be an experiment for a machine builder. We wanted proven five-axis machining technology; Mikron had many machines successfully operating in the USA, they had an excellent service team, and the HSM 400U was in stock."
The first machine was installed at ECC in the spring of 2002. Subsequently, the company purchased a second HSM 400U, installed in January 2003, to provide the necessary additional capacity the company had grown to require in less than one year.
Incorporating the machining centers into ECC's manufacturing operation has significantly reduced production time while improving surface finishes. "Bench work has been eliminated, reject rates are lower, our labor costs have been reduced, and our part quality is far better," says Rosenholm. "Previously we had to perform multiple setups with the four-axis machine. Now we can achieve what we need in just two setups with the five-axis machine."
The machines have also allowed ECC to set up manufacturing cells that have eliminated outsourcing. "We use a cellular manufacturing approach for one of the parts that combines close-tolerance turning, jig grinding, electric discharge machining [EDM], and honing," Rosenholm explains. "By adding five-axis machining to our process, we're able to handle all types of work in-house, and have eliminated the need for outsourcing any aspect. We're able to handle highly engineered parts, such as mold cavities and cores of hardened steel, machine them directly with the Mikron machine, and see cycle time savings of 80% versus making electrodes using EDM."
The Mikron HSM 400U combines simultaneous five-axis machining and high speed. According to Rosenholm, the machine fits right in with ECC's quality philosophy. "We check everything 100%," he says. "Quality is at the heart of our reputation along with our ability to deliver when promised. There's no doubt the addition of simultaneous five-axis high-speed machining technology to our operation has enhanced our ability to go beyond the ordinary."
Cast Polymer is Solid Foundation
When New Vista Corp., a Baltimore-based custom machine builder, originally proposed a high-production automated groove and trim machine for producing large (11/2 - 4", or 38 - 102-mm) pipe fittings, there was a lot riding on the outcome. If company management at one of the world's largest producers of mechanical pipe joining products could not justify the project, the casting and machining for this product line would be transferred offshore.
New Vista got the job, three machines to be supplied over a 21/2-year interval. As a custom machine builder, the company must evaluate the feasibility of different designs and materials in every area of each machine it builds, to make sure that its design best serves the application. One issue: what type of machine base to use?
Up to this point, New Vista had used cast iron or welded steel bases in all of its designs--standard approaches that yielded satisfactory results. But engineers were intrigued by the possibility of utilizing a cast polymer composite base for this application. "We knew the benefits of it, and this application seemed a perfect opportunity to test the waters," says VP of Engineering Jim Brun.
In the US, there are two primary sources for custom polymer castings, both in northeast Ohio: ITW Polymer Castings (Chardon) and Anocast (Chagrin Falls), a division of Rockwell Automation. New Vista contacted both companies and selected ITW.
| As-cast polymer composite base for high-production automated groove and trim machine (left), and finished machine being rigged for shipping.
ITW recommended use of a wood mold, and influenced the direction of New Vista's design. Since cast composite is not as stiff as cast iron, much thicker cross sections are employed. But, unlike cast iron, varying thickness won't cause internal stresses. New Vista used a 64 X 61 X 26" (1.6 X 1.5 X 0.7-m) block with six foam cores, cross sections of no less than 8" (204 mm), cutouts for forklift tines, and adjustable mounting feet. Featuring about the same density as aluminum, the base weighed in at 6500 lb (2925 kg). "We wanted the base to stay heavy to try to capture as much vibration damping ability as possible," Brun explains.
Total cost of the first composite base was $13,500, including $4500 for a wooden mold, $1600 for finish grinding the top surface flat to 0.0025" (0.064 mm), and $500 for secondary machining.
New Vista had estimated cost of a traditional base at $10,000. Was the polymer base worth the additional $3500? New Vista engineers believe the cost was justified in terms of vibration damping ability, which is five to 15 times greater than cast iron and results in better part surface finish, longer tool life, and decreased noise levels.
Although part surface finish is not a critical objective for the customer, tool life is important. Six tool slides employ $220 worth of tooling inserts to perform a number of operations on the fittings, including trimming the end gate, machining grooves, turning "collars," and applying inside and outside chamfers. With one ferrous fitting being finished every 11 sec on a three-shift basis, even a 10% increase in tool life is significant.
Drills Cut Superalloy Machining Cost 80%
Switching to a new carbide drill with a geometry designed to reduce machining thrust has helped an aerospace components manufacturer reduce the cost of drilling high-temperature alloy parts by more than 80%.
Previously, J.F. Fredericks Tool Co. (Farmington, CT) used three operations--center drill, drill, and ream--to make a 0.1875" (4.76-mm) diam hole in an Inconel 718 component. The drilling operation was limited to 28 sfm (8.5 m/min), and drills produced an average of 18 pieces between regrinds. Tooling and machining costs for the 2000-piece annual volume ran to more than $2000.
In an effort to reduce costs, the company decided to try Kennametal's new Sculptured Edge (SE) 284 Dynapoint drills, which have a special positive-rake chisel point with an extremely large active cutting area that substantially reduces stress and provides freer chip flow on high-temperature alloys. The new drills eliminated the need for center drilling and reaming, allowed an increase in cutting speed to 75 sfm (23 m/min), and increased tool life to 150 pieces per regrind. Drill cost fell from about $0.15 to about $0.11 per part. More importantly from a cost standpoint, machining time was reduced by more than 90%, from 54 to 5.1 sec per part.
"The bottom line was that these new drills reduced our annual machining costs from $2096 to $396," says manufacturing foreman Frank Klopp.
J.F. Fredericks specializes in producing aerospace components such as elbows, fittings, rings, and fuel nozzles from superalloys and titanium alloys. Customers include Howmet Corp., Chromalloy, US Navy, IMO, Kamatics Corp., Samsung America, Volvo Flygmotor AB, Fiat Avio SpA, Watervliet Arsenal, Textron Lycoming, United Technologies, General Electric, and many others. The company has 75 employees, a 25,000 ft2 (2325 m2) climate-controlled building, and CNC equipment including mill-turn machines, grinders, horizontal machining centers, drilling machines, and turning centers. The company also provides process engineering, tool design, CNC programming, and document control services.
Used to fixture the part for a later operation, the previously mentioned hole is produced using a Tsugami FMA5-II horizontal machining center. The machine features a spacesaving vertical pallet magazine that enables untended machining and also allows chips to drop directly onto the chip pan.
The part material, Inconel 718, has a hardness of RC 38. "This is a very difficult material to drill," Klopp says. "Its high nickel content makes it very gummy, so it tends to chip or break inserts. In an effort to avoid that, we ran the cobalt steel drills at a relatively slow speed and feed, which increased machining time. But they still used to chip or break very quickly around the flutes, cutting lip, or at the outside corners." The drills also had a tendency to walk or wander at the beginning, forcing Fredericks to adopt a center drilling operation, he adds.
Klopp felt there was considerable room for improvement on the drilling operation, so he spoke to a Kennametal sales engineer and found out about the SE drills. The tools have a higher positive rake angle than existing products, making them well-suited to cutting aerospace materials.
Testing showed the drills performed as expected, eliminating the need for a centering operation and allowing substantial increases in cutting speed and feed rate. Even with higher speeds and feeds, the tools produced 150 holes. The drills cost $67.50 and can be reground 8 times, for a tool cost per hole of $0.109. But the big advantage came in the reduction of machine time.
Fredericks also takes advantage of Kennametal's regrinding service to ensure that the drills are reground to original factory specifications. Because Kennametal knows the drills' original geometry, it can regrind the tools with more precision than an outside tool-regrinding service.
Sensor System Cuts Costs, Waste
Precise determination of inclinations is a critical requirement for Seagate Inc. (Bloomington, MN), a vertically integrated builder of hard disk and tape drives for data storage.
Precise determination of inclinations is a critical requirement for Seagate Inc. (Bloomington, MN), a vertically integrated builder of hard disk and tape drives for data storage.An outside vendor manufactures wafer substrates by a unique hot pressing process and supplies them to Seagate, which builds up its recording head structures on them. The company's ceramic grinding operation on the finished wafer is extremely sensitive. The 4.5" (115-mm) square wafers, which are worth thousands of dollars each, are ground down to 1250 µm. If the sensitive Stausbaugh 7AF wafer grinder used in the process is not set at precisely the required angle, it may take hours to make the required adjustments. The labor cost for highly trained technicians needed in the production process becomes insupportable.
When Seagate purchased the Wyler Zerotronic Sensor System from Fred V. Fowler Co. (Newton, MA), it substantially increased the efficiency of its tightly controlled and fine-tolerance processing operations. The sensor handles small angles with a high resolution as well as large angles. A temperature sensor mathematically compensates for changing environmental conditions, which improves measuring results.
At Seagate, the digital inclination sensor fulfills one critical function: to accurately measure the relative angle between the chuck holding the wafer and the grinding wheel axis. "The spindle angle is important because of the type of grinding we use to produce the wafers," explains manufacturing engineer Mike Kwilinski. "We must use a minimum spindle angle that best complements the hardness of the self-dressing grinding wheel. One of the keys in setting up the grinders is to measure a precise angle between the grind spindle and the work chuck."
If the spindle angle is too small, the wheels won't break down and expose new grinding media to the workpiece. When a 60-lb (267-N) down-force on the machine is reached, the grinder stops and must be unloaded manually.
If the angle is too large, the wheel breaks down too quickly. "With wheels costing $1100 each, their ability to function properly becomes a big factor," Kwilinski says. "The spindle angle also helps determine wafer thickness uniformity, which is absolutely necessary. The Zerotronic sensors basically let us know where we're at, and this is a vital bit of information we need to set up the grinders properly and to know where the wheel spindle is in space," he adds.
This article was first published in the January 2004 edition of Manufacturing Engineering magazine.