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Shop Solutions: Tooling Improves Aerospace Shop's Processes

 

Mikelson Machine Shop Inc. (South El Monte, CA) is a 100% aerospace contract manufacturer that continually looks for ways to improve production of its highly complex manifolds, valve blocks, and other hydraulic aircraft components. Founded in 1953 by owner James Mikelson’s grandfather in his garage, the shop occupies a 12,000 ft2 (1115-m2) facility and employs 26 people, including James Mikelson’s wife Josie, his son James and his fiancé Kathy, and daughter Jackie.As head of Mikelson’s Continuous Improvement Department, Jackie Mikelson keeps a close watch on its part manufacturing processes. In her role as process and improvement planner, she monitors all individual part manufacturing operations, including evaluating part drawings, CNC programs, machine setups, and machining cycle times in an effort to reduce overall job leadtimes.

According to Mikelson, his daughter’s work has paid off. The shop’s overall leadtimes for jobs from start to finish have dropped from between 16 and 18 weeks down to 8 weeks or less. He credits a big part of this improvement to incorporating the best tooling possible for every part operation, no matter how secondary some of those may seem.Mikelson family continues tradition of aerospace shop management: Front row, James Mikelson (left) and son; front to back: wife Josie; daughter Jackie; son’s fiancé Kathy.

"We have all high-end machine tools, and we don’t use run-of-the-mill tooling on them," said Mikelson. "A general-purpose machine running general-purpose cutting tools will yield general-purpose results. We’re doing a lot of high-feed milling and plunge milling as a result of our customers transitioning from castings and forgings to components manufactured from solid block and bar materials. And those machining techniques require advanced tooling, which is why we get almost all of our tooling from Seco Tools." 

Job lot sizes are typically 8–48 pieces, and the lion’s share of Mikelson’s part processing is milling on five-axis horizontal machining centers and four-axis horizontal and vertical machines. Components are made from nitride and carburizing steels, stainless steels such as 15-5 and 17-4, and 6061, 7075, and 2024 aluminum. Part sizes range from 2 to 14" (51–356 mm) and 10" (254-mm) long, with required tolerances between ±0.001 and 0.00005" (0.03–0.001 mm) and surface finishes from 32 to 2 Rms.

Mikelson uses Seco’s high-feed/plunge cutters, aluminum router cutters, solid carbide drills for hole sizes from 0.070 to 1.00" (1.8–25.4 mm) in diameter and indexable tooling for 0.750 to 4" (19-101.6-mm) diameter bores 8" (203-mm) deep. In addition, the shop runs Seco 4" (101.6 mm) and 5" (127-mm) disk cutters, square-shoulder slotting cutters, Jabro solid-carbide end mills from 0.039 to 0.787" (1–20 mm) diameters, thread mills, shrink-fit toolholders, and Seco’s Jetstream tooling high-pressure coolant-delivery technology for turning operations.

When considering the incorporation of a new tooling technology, Jackie Mikelson evaluates it by comparing previous runs versus runs with the change in tooling to determine if a particular tool is worth the investment. If there’s an improvement with the particular part operation she’s testing, she tracks the results in a database and then applies the tooling change across the board to all other jobs with the same operation.

The first thing Jackie looks at is the part program, comparing it to the part drawing to see where a change in tooling would speed the process. She pays special attention to cutter inserts and looks for those from Seco that will allow for increasing speeds and feeds, incorporating Seco drills wherever possible to eliminate pecking operations.

With these simple changes, she often shaves minutes off of each and every part operation. In one instance, these savings in individual operation minutes added up to reductions of hours in total part-processing time for a component the shop refers to as "Jackie’s part" because it was the first one she evaluated in her process planning position.

Requiring 120 tools for processing, this proprietary and extremely complex aircraft part took 5 hr to machine. By streamlining setups and using Seco tooling, Jackie was able to slash that time down to 3 hr. The longest operation takes 1.5 hrs, and most of the others she was able to keep to less than 30 minutes apiece. The part also requires drilling and finishing deep bores to within ±0.0002" (0.005 mm).

"We now strive to keep major machining operations to within 30 minutes or less for all our complex parts," said Jackie. "And the basic setup improvements made, along with the Seco tooling, for this particular component have been easily applied to others."

Through Jackie’s work, the shop has realized that it gets the most significant results when incorporating Seco tooling throughout all a part’s various operations, not just one or two. Such successes range from drilling 0.375" (9.5-mm) diameter holes at 18×D in just 6 sec to thread milling holes at 9000 rpm with Seco thread mills. This process can be done in seconds rather than in minutes using standard straight-flute thread mills. They can also drill 0.062" (1.6-mm) diameter holes in 1 sec using Seco’s solid-carbide Feedmax drills, as opposed to 40 sec with standard drills and having to peck.

"In the last three years, our use of Seco tooling has really taken off, and we rely heavily on them for application advice," said Mikelson. "We have confidence in their tooling because they conduct extensive testing on it, doing all the time-consuming legwork for me. All that knowledge and expertise they then pass on to us for improving our processes."

To illustrate, he cited the shop’s incorporation of high-feed milling and plunge milling. With Seco tool technology coupled with expert application guidance, the shop now high-feed mills taking 0.020–0.030" (0.51–0.76-mm) depths of cut, feeding at around 180 ipm (4.6 m/min) and plunge mills as opposed to interpolating around part profiles to machine parts faster from solid raw materials. "Jackie's part" benefited from careful attention to process improvement and can now be completed in 3 hours vs. the 5 hours it previously required.


Seco High-Feed milling cutters allow Mikelson to cut up to three times faster compared with conventional machining methods. High-feed milling is the combination of shallow depths-of-cut and high feed per tooth, which results in higher metal removal rates. Also, using plunge milling directs cutting forces at the machine spindle in the axial direction for greater stability and reduced vibration, contributing to extended tool life and faster metal removal rates.

The two milling techniques are credited by Mikelson with taking "huge amounts of time and tooling costs out of Mikelson’s processes." In addition, the Seco tools generate better surface finishes, so the shop is often able to eliminate secondary operations/machines such as grinding and honing.

The shop has taken all of its tooling off the shop floor and placed it in dedicated holders. Tools are preset in a toolroom, stored in carts that hold hundreds of tools and holders for each job and are grouped according to part numbers. These carts allow tooling to easily move where needed and free up valuable shop-floor space.

Many of the holders are Seco shrink-fit, and Mikelson said they provide more consistency and accuracy. He added that the holders enhance the performance of Seco tools and deliver a positive balanced grip when running at 12,000 rpm and higher spindle speeds.

"For a long time we operated under the assumption that we knew everything about cutting tools and how to use them," said Mikelson. "Now, when Seco makes a tooling or machining parameters suggestion, we listen because it usually results in process improvements. And we are all about process improvement." ME For more information from Seco Tools Inc., go to
www.secotools.com, or phone 248-528-5444; for more information from Mikelson Machine Shop, go to www.mikelson.net, or phone 626-448-3920.

 

Five-Axis Cuts Shop’s
Medical Devices

Oak View Tool Company LLC (Columbia City, IN) designs, prototypes, and manufactures special surgical cutting devices and orthopedic carbide tools. President Matt Dahms, an engineer and machinist, maintains close contact with the company’s medical device OEM customers and surgeons to continuously create new and improved tools that work more efficiently and are easier to use by surgeons and easier on their patients.

Matt Dahms, president, Oak View Tools, recognized the opportunity to bring machining work formerly outsourced, back in-house with the Mazak Integrex 200-IV S Multi-Tasking machine.Oak View Tool’s product line includes surgical rasps, reamers, and broaches, tools all used to cut or remove human bone as part of the preparation for installing orthopedic implants. The shop will develop a new tool or enhance an existing design, then produce a couple hundred for testing. However, more customers are having Oak View Tool also run production, which means the shop is now averaging about 110–120 jobs per month that can entail 1–5000 pieces per order.

With approximately 15 CNC machine tools and 25 employees, the ISO 9000 and 13485:2003-certified shop does all the machining in-house necessary to produce its surgical tools. Processes include five-axis milling, turning, drilling, five-axis grinding and inspection. And while no machining work is outsourced these days, that wasn’t always the case at Oak View Tool.

In 1996, Oak View Tool started as a regrind shop specializing in carbide cutting tools and eventually took on the challenging task of also grinding stainless steel. These two materials are now the only two the shop currently works with. Eventually, many medical OEM customers requested that the shop also do the machining work, which Oak View Tool would then outsource to local shops, keeping only the grinding work in-house.

As business increased, Dahms considered bringing all outsourced machining work back in-house. Not only would doing so improve the shop’s profitability, but, most important, it would help maintain and further improve upon the high quality and integrity of the surgical tools and devices the shop produces. In 2010, the decision was definite when Dahms saw the capabilities of the five-axis Integrex 200-IV S Multi-Tasking machine from Mazak Corp. (Florence, KY).

He realized that this one machine would accommodate all the returning outsourced work and perform the shop’s hard-machining operations. All stainless steel and carbide parts are cut in an Rc 40–45 hardened state. The Mazak machine provides the speed, torque, rigidity, accuracy and significant machine mass for hard machining that is often lacking in basic level machines on the market.

"We considered a Swiss-style lathe, but that type of machine would have limited us in terms of part processing," said Dahms. "We knew the complex geometries of our surgical tools and devices required a machine with five-axis capability, specifically the B-axis milling spindle movement the Mazak Integrex 200-IV S provides." In addition, Dahms said the Integrex 200-IV S would easily maintain the shop’s required tolerances of ±0.0005" (0.013 mm) and accommodate its part sizes that can range from 1 to 24" (25.4–610-mm) long and from 0.187 to 4" (4.75–101.6 mm) in diameter.

The Integrex 200-IV S is a twin turning spindle machine with a milling spindle and 20-tool capacity ATC. The milling spindle delivers 12,000-rpm cutting speed, 25-hp (18.6-kW) and 88 ft-lb (119 N•m) of torque for the shop’s hard-machining operations. The spindle provides 225° of B-axis travel, indexing at 0.0001° increments.

"Actually, my experience with Mazak machines started way back when I was working in the automotive industry. While doing so, I used to hard-mill on Mazaks all the time, and even back then Mazak’s mills and lathes had the rigidity and torque to handle the tough task," said Dahms. "We were doing hard-machining way before it was as common as it is today."

Oak View Tools’ Integrex 200-IV S not only hard-machines all the shop’s surgical tools and devices, it does so in significantly fewer operations while also eliminating the need for multiple machines and setups. Workpieces that would require as many as four operations on a lathe and four operations on a milling machine are completely machined on the multitasking Mazak in two. And for a specific hip broach currently done on other machines, the shop plans to move it to the Integrex 200-IV S, which will reduce the broach machining from 10 operations down to only one.Medical devices like these hand rasps have benefited from continuous improvement in design at Oak View Tools. 

The Integrex 200-IV S at Oak View Tool is located in a cell along with a five-axis grinder. Having the two machines in close proximity allows one machinist to operate both machines. All tools and devices the shop produces are ground, so once the Mazak machine completes machining operations, parts are quickly transferred to the grinder for finishing.

In part processing, Oak View Tool machinists often use the twin turning spindles on the Integrex 200-IV S for work support when machining the shop’s longer tools and devices, some of which are up to 24" (610-mm) long. The equal speed and synchronized C-axis motion of both spindles allow the machinists to chuck one end of the part in one spindle and the opposite part end in the second spindle as the machine’s milling spindle works on the part. Or the twin spindles are used for sequential operations, performing first Op/front side work in one spindle, then a coordinated part transfer to the second spindle for the second Op/back side work.

Dahms’ observations of orthopedic surgical tools and devices in action and his consultations with surgeons and OEMs have led to several improvements and enhancements of how existing tools and devices are used and how they perform. For instance, an engineering goal at Oak View Tool is to lessen the need for surgeons to have to use a hammer on surgical tools or devices.

To remove bone material in preparation for implants, many surgical tools and devices require surgeons to use hammers. Such tools and devices are typically designed to accept strike plates strictly for this purpose. However, having to use hammers on tools and devices is hard on surgeons and equally hard on patients.

"We are now helping develop surgical tools and devices that make a difference, because they lessen the need for having to use a hammer on them. Many designs of today’s existing surgical tools are such that they could be improved in regards to ergonomics," said Dahms. "Their geometries are often insufficient and could be better. With our extensive surgical tool background and the machining capabilities of our Mazak machine, we are able to improve the geometries of these tools and, along with that, their performance."

As an example, Oak View Tool recently improved an existing tool that previously removed bone material in only one direction. "By simply optimizing its teeth geometries, we were able to produce the same tool that now removes bone material in both forward and back directions. It’s both more efficient and less stressful on both surgeon and patient."

Production-run jobs have increased at Oak View Tool and business has grown, but Dahms said that the shop will always focus, first and foremost, on R&D and prototyping for the medical industry. The machining capabilities of the Integrex 200-IV S allow the shop to quickly produce prototypes of new and improved surgical tool and device designs that couldn’t otherwise be made in the past.

"Our R&D, prototyping and production capabilities give us a significant competitive advantage," said Dahms. "We will continue to stay on the cutting edge by incorporating the latest innovative machine tool technology such as that from Mazak. For the very near future, we are moving into ultra-high-speed machining and already have another Mazak machine in mind for that."  ME  


For more information from Mazak Corp., go to www.mazakusa.com,
or phone 859-342-1700. 

 

This article was first published in the December 2012 edition of Manufacturing Engineering magazine.  Click here for PDF


Published Date : 12/1/2012

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