Shop Solutions: CNC Cuts Surgical Tools Faster
Advanced CNC machining is enabling Stryker Corp. (Kalamazoo, MI) to achieve 20% reduction in cycle times in producing its surgical tools, improving R&D results, and increasing production output.
Stryker is a global leader in manufacturing medical devices and equipment, ranging from orthopaedic implants to all types of surgical apparatus and patient-care devices. Stryker's products, which are found in medical care facilities around the world, are used primarily for orthopaedic, spinal, neurological, and ENT procedures, plus minimally invasive interventional pain procedures.
The Stryker Instruments Division operates five facilities, located in Kalamazoo, Texas, Puerto Rico, Germany, and Ireland. The division produces surgical tools, including cast cutters, inflow/outflow cannulae, burrs, drills, saws, and microdebriders. Its customers are surgeons and operating room equipment specifiers, as well as otolaryngologists (ear, nose, and throat or ENT), and emergency medical vehicle outfitters, among others.
Manufacturing requirements for its System 6 power tools frequently call for low-volume production. These highly specialized devices include high-precision hand-held devices like oscillating bone saws. This scenario presents an ongoing challenge for the Product Group's management team at the company's main manufacturing location in Kalamazoo. This location is also home to the company's Experimental Group, which investigates new technologies, advanced materials, and various manufacturing protocols to maximize production. Production Part Approval Process (PPAP) protocols are also strategized here.
The Experimental Group provides components to Stryker R&D engineers for testing and evaluation, including prototyping surgical tools for field evaluation and aesthetic feedback by surgeons, though not for formal trials or surgical use.
In its tool production, the company uses a variety of substrates, including 300 and 400 series stainless, 6061 aluminum, and titanium, plus specialty materials such as Inconel, Nitinol, ALG alloys, and others. Assorted thermoplastics such as Delrin, ABS, Teflon, and thermoplastic elastomers, are also machined here where production processes are strictly monitored for compliance to FDA standards.
As a result, Stryker maintains a variety of machine tools and other metalworking equipment at its Kalamazoo facility, including basic milling and drilling equipment, alongside three and five-axis CNC machining centers and EDMs.
One of the newest advanced CNC machines in the Experimental Group is a Model DMC 635 V eco, a threeaxis VMC with an 8000-rpm spindle and a 20-position toolchanger from DMG America (Itasca, IL). Control is supplied by the Sinumerik 810D CNC from Siemens (Elk Grove Village, IL) and ShopMill software.
"We typically store a few programs on the CNC and keep our backlog of programs on a network drive for easy recall, says Rich Mitchell, supervisor of the Experimental Group. "Our group supports about 60 engineers, so the communication between departments is constant and quite fluid. We take IGES or PRT 3-D files and program directly from the digital content, using MasterCAM and now the Siemens ShopMill program that is right on the machine. The Sinumerik 810D control receives excellent ratings from our operators and has quickly become their control of choice, especially on the fast and flexible three-axis eco milling machine from DMG."
The part and tool setup pages are intuitive and incorporate graphic depictions for specific data inputs, reducing the learning curve for the operators. "Most of our guys had never used a Siemens control previously, so it is ironic that this CNC is now their favorite. They literally line up to use it," says Mitchell.
Program transfer from the Stryker network back to the CNC is quick and easy. "This is very advantageous in the Experimental Group, where most jobs are one-offs or very small quantities," says Mitchell. "Operators can write and run multiple programs through each CNC daily, saving time on entering and editing setup data onto the machine. The very nature of this department, as it conducts various experimental trials to seek out the best production methods and machining strategies, mandates extremely fast turnarounds," says Mitchell, who credits the Siemens CNC for facilitating this process.
"We currently have four other controls in our milling department, so it's easy to imagine the challenges our guys face daily. The Siemens numerical control has worked quite well for us with a manual touch probe and manual Z-axis presetter for tooling. As we expand or replace current milling technology in our production, we will most likely transition to a Siemens 840D with a Renishaw touch probe and tool presetter to expedite setups," says Mitchell. The seven operators in the Experimental Group were all given training on the programming of the CNC by DMG America Inc.
This machine joins multiple DMG Twin 65 and Twin 42 turning centers, each with an upper B-axis to complement the Y-axis and driven tools, which are required to create the contours and sophisticated geometries needed for Stryker's surgical tools. The turning machines have the Siemens Sinumerik 840D onboard, which enables precise and transferable control of spindle and axis movement variations via compile cycles, so Stryker Experimental engineers can make rapid changes in their production scheduling.
Randy Carpenter, a senior project engineer for Stryker Instrument's Production Group, explains its manufacturing example: "We run families of parts, most often. We have one set of parts, run in 416 and 17-4 [grades of stainless] with RC 38 hardness. We're typically running dimensional tolerances down to the ten-thousandths, so it's very precise work. Compared to the older machines and controls, we have tracked our cycle times in relation to our target Cpks and we are getting better than 20% reductions with the DMG machines and Siemens CNC onboard. Plus, we already see the improvements in surface finish, owing to the smoother translations line to line in the milling and turning programs." Carpenter also says his production department has been able to achieve considerably higher changeover efficiencies that allow more jobs to run per shift. "System 6 has become a big seller for Stryker and our ability to ramp up production to meet demand with the DMG machines with Siemens numerical controls has been a big plus," Carpenter concludes.
For more information on DMG America Inc., go to: www.dmgamerica.com or telephone 815.637.8555; for more information on Siemens Industry Inc., go to: www.siemenscnc.com or telephone 847.640.1595.
Software Engine Ups Feed Rate 10X
The tool room is the hub where all of the internal tooling takes place at a metal-stamping and fabricating facility. Manufacturing processes include metal-stamping dies, press-brake tooling, tube-bender tooling, and weld and machine fixturing for a variety of different applications.
Performance Tool and Die (PTD; Detroit Lakes, MN) was looking for ways to reduce cutting forces, increase tool life, and reduce cycle time—seemingly contradictory objectives. "Because we are in a tool-room setting, every block we do is different from the last." Arlin Hillukka, CNC programmer at PTD, explains: "We are not able to do block-specific fixturing, so most components are held in a vise. With a five-axis vertical mill, the block-holding problem becomes magnified, because we are trying to mill more features on the block than would normally be done in a three-axis machine. Blocks often are left hanging out of the vise or fixture farther than normal, which is a less than optimal situation with respect to cutting pressure."
The need to reduce pressure and cycle times led PTD management to evaluate VoluMill, a plug-in toolpath engine from Celeritive Technologies (Cave Creek, AZ) that is integrated in GibbsCAM. The software was recommended by GibbsCAM reseller, Midwest CAM Solutions (Brooklyn Center, MN). VoluMill is a new genre technology that generates toolpaths with smooth motions and low force on the spindle and cutting tool, reducing cycle times and extending the life of cutting tools.
VoluMill was developed to eliminate the poor machining conditions that traditional toolpaths have produced since the advent of numerically controlled milling machines. VoluMill, which can work with any CAM system, reportedly generates toolpaths with ideal machining conditions, enhancing machine utilization and shop productivity.
"Our reseller told us other customers were seeing tremendous gains, so we decided to take advantage of VoluMill's free trial offer," Hillukka says. "We were very skeptical of the advertised time reduction and extended tool life, but after using it for a short time we found it to be the real deal."
Almost immediately, PTD was running at feeds 10 times faster than before. In some cases, PTD experienced even greater savings. Running a large pedestal punch made of A2 tool steel used to take 22 min 36 sec to run with a 3" (76.2-mm) inserted shell mill.
With VoluMill, the same process took only 7 min 20 sec with 0.5" (12.7-mm) solid-carbide ball end mill, delivering a 208% increase in efficiency. Once the trial period ended, PTD purchased three VoluMill seats.
"The benefits exceeded our expectations." Hillukka explains: "Our traditional method of rough-milling a pocket in a plate or block would be to take passes of 0.100–0.150" [2.5–3.8-mm] depth of cut and 50% cutter diameter peripheral cut. By doing this, we used the bottom 0.100–0.150" of flute over and over again, causing them to wear while the rest of the cutter was virtually untouched. Now, we drop the cutter all the way into the block for full flute engagement and, depending on the cutter, take 0.020–0.080" [0.5–2-mm] peripheral cuts."
"Because the VoluMill software keeps a consistent peripheral-cut amount, we can push our cutting tools to the maximum capacity without having to worry about heavier cuts in sharp corners in the toolpath. This has extended our cutting tool life significantly," Hillukka continues.
More important, PTD found that machining with VoluMill toolpaths produced less cutting pressure on the part than when cutting with traditional toolpaths, which eliminated the block holding issues they were experiencing. This benefit significantly affected their production of these parts, including the amount of scrap they were generating because of the block holding problems.
Although PTD does not track scrap numbers, it estimates that scrap due to blocks tipping out of fixturing has been reduced by roughly 25%.
The smooth tool motions generated by a VoluMill toolpath allowed PTD to increase the feed rate 10 times, while taking 80% smaller peripheral cuts at four to eight times the depth of cut, depending on the cutter being used.
"With the extreme speeds and feeds that are used, customers and others are very impressed with what we are doing," Hillukka concludes.
For more information on Celeritive Technologies Inc., go to: www.celeritive.com, or telephone 888.253.6701.
Saving Time, Money, and Lives
Controlling and improving the management of inventory while reducing the number of second-day and next-day shipments due to stock shortages is every company's challenge.
It's especially important for Holmatro Inc. (Glen Burnie, MD), a leading global designer, manufacturer, and distributor of UL-listed and NFPA-1936-compliant hydraulic rescue tools. Founded in 1967, Holmatro manufactures a full line of hydraulic rescue tools, heavy lifting equipment, pneumatic lifting bags, and shoring equipment and maintains a significant amount of equipment available for emergency deployment 24/7. The company manufactures in three factories on two continents.
Holmatro management determined that to meet demand for its critical life-saving products in a timely manner meant that its cutting tool inventory process needed to be improved. To keep better control of its tooling inventory, the most logical answer was to hire additional personnel to maintain and check inventory levels. Then a new idea was proposed: a tool management system that allows ease of use and a way to control and maintain tool inventory levels while tracking usage.
After reviewing several systems, Holmatro selected the Matrix tool management system from Iscar Metals Inc. (Arlington, TX). The Matrix was ultimately chosen for the software, cabinet design, and the support and training that accompanied purchase of the system.
Matrix combines the automated tool dispenser with management software to control inventory, streamline purchasing, and drive down costs.
Access to an item stored in Matrix's locked bins is electronically controlled by the management software according to pre-defined authorizations. Matrix features a flexible system that offer a variety of drawer and bin configurations. Addon cabinets are connected with a click of a cable.
"We researched many products that offered distribution, inventory control, and tracking," says Chuck Cain, Holmatro manufacturing engineer. "After we saw the demonstration of the Matrix in action, we knew this was the product for us. Our machinists were issued badges with bar codes for easy log in and we received 14 hr of in-house training. We also utilized the existing bar codes and EDPs of our tooling. The reports worked as promised, giving us three emails per day to address shortages as well as one transaction report. Matrix interface and the touch screen are easy to understand at any skill/experience level. Custom scripts made our valuation reports accurate and current. Overall, our Matrix experience will lead us to budget and purchase a second cabinet in the coming year."
All of the last minute stock issues disappeared, according to Cain. All of the operators took a closer look at how the tools were being used as well as when they were changing tools resulting in a better CPU. Now Holmatro had the ability not only to know they had certain tools in inventory, but the ability to track which tools were being used on which machines throughout the manufacturing facility.
By investing in the right equipment, Holmatro has saved an estimated 520 hr of additional labor and created an estimated $108,000 annual savings. The Iscar technical Matrix team facilitated implementing the software and equipment.
Benefits of the Matrix include improved or increased 3Ps (performance-productivity-profitability) through lower tooling costs. Typically, employees become more aware of tooling usage, costs, and impact on production. Stock shortages and shipping costs are reduced, and problems become more apparent and are addressed in a timely fashion.
For more information on Iscar Metals, go to www.iscar.com or telephone 817.258.3200.
Going Lean with Large-Part Machining
Weak economies have hit the manufacturing industry hard, especially in Michigan. Machine shops with the flexibility to accommodate change, diversify their customer bases, and run lean with efficient operations, however, are well-positioned to survive when times get tough.
Merrill Tool (Merrill, MI), a 40-year-old grinding, milling, and turning shop followed a strategy of diversification and lean operations even before the economy began to decline. The company has been able to leanout machines, setups, floor-space, and cycle times with fewer, morecapable, boring mills, VTC's, and a large-part HMC, increasing capacity and opening new markets.
The shop boasts of flexibility to handle parts from under an ounce to more than 50 tons, from under 1" (25.4 mm) to more than 40 ft (12 m). As part of the 400-employee Merrill Technologies Group, the company is sister to Merrill Fabricators, Merrill Engineering & Integration, and Merrill Aviation. Merrill Tool President Bob Yackel has steered a course to diversify his customer base so that no segment of industry constitutes more than 20% of the company's sales, focusing on aerospace/defense, machinery-build, automotive, heavy equipment, and oil field as key markets, while rapidly expanding Merrill's work in emerging wind/solar energy.
As a two-shift contract shop with a high proportion of large-part work, Merrill constantly fine tunes its machining strategies and capabilities to make margins on large-part lots as small as one. Tuning up its capacity for an increase in oil-field work, Merrill purchased a MAG RT 1600 boring mill from MAG Giddings and Lewis (Fond du Lac, WI) at IMTS 2006. This increase in capacity continued with a second similar boring mill, two vertical turning centers with 2-m tables and, most recently, an HMC with twin 1250-mm pallets. All were acquired from MAG between late 2006 and early 2009, representing a total investment of approximately $7 million.
The rotary-table horizontal boring mill immediately replaced three retrofitted boring mills, and in doing so increased part processing capacity and reduced machining time by as much as 34%. "We purchased our first MAG boring mill to handle new work involving some very large valve parts," says Yackel. "The capacity of the rotary table, W-axis travel, and overall technology are the main reasons we bought the MAG machine. We also liked that it was made in the US and was immediately available, because we had an immediate need."
The RT 1600 has a fully programmable 1600 x 2500 mm contouring rotary table capable of handling parts up to 25,000 kg, which has helped reduce cycle times by providing the ability to machine four sides of the workpiece without re-fixturing. There are four options for the W-axis saddle travel: 1500 mm, 2000 mm, 2500 mm, and 3500 mm. The single-piece cast bed, with a wide 1310-mm way spread, adds to the machine's rigidity and accuracy.
"We've used the RT 1600 to machine parts up to 42,000 lb [19,050 kg] in one setup," says Yackel. "It holds bore locations to ±0.0005" [0.013 mm], and we can program offline for even better chip-to-chip times." Merrill also uses spindle probes for setup and post-process measurement.
Merrill added a second RT 1600 in December 2008 to provide increased machining capacity for a new wind energy customer, a growing part of Merrill's industry mix. Manufacture of wind-energy parts now accounts for about 10% of the shop's business, where it was zero percent just five years ago.
The two RT 1600 boring mills have consistently cut cycle times, reduced setups, and made it easier to achieve specified part accuracies. They have 155-mm, four-speed spindles with up to 56 kW of power and 7695 Nm of torque. As an example of reduced cycle times and setups, Yackel cites an aluminum fabrication that had previously run on one of the shop's retrofitted boring mills. The new mills cut cycle time 34%, from 22 to 14.5 hr, and eliminated a setup. For another customer, ordering fabricating machine columns one at a time, Merrill used the boring mills to cut cycle time 16%, eliminate a setup, and easily hit the required squareness of 0.0004" (0.010 mm), which had been a problem with the previous machine.
The relationship between MAG and Merrill has expanded beyond "machine tool provider and job shop customer," with Merrill now machining parts for MAG machines—a case of having the right equipment to meet customer needs.
For more information on MAG, go to: www.mag-ias.com, or telephone 920.921.9400.
This article was first published in the December 2009 edition of Manufacturing Engineering magazine.
Published Date : 12/1/2009