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Twin Disc, a manufacturer of marine transmissions, grinds shafts of all lengths, weights, shapes and sizes. According to the company, the only thing all these shafts have in common is precision—very close tolerances and unforgiving surface finishes. Flawed shaft production can result in transmission failure. Thus, Twin Disc strives to use the best grinding technology available. So, when a bottleneck arose from a labor-intensive shaft-production process involving multiple setups, the company invested in a new grinder equipped with a full B axis. Since then, it has consolidated the troublesome operation from three machines to one.

Based in Racine, Wisconsin, Twin Disc has been in business for more than 75 years making more than 30 different marine transmissions for pleasure craft, military vessels, tugs, pushboats and more. In fact, Allied forces depended on the company’s transmissions to drive some 40,000 landing craft loaded with troops and supplies onto beaches during the Normandy invasion and throughout the South Pacific during World War II. In addition to marine vessels, the company makes transmissions for mining industry trucks and for various military vehicles, including the Bradley armored personnel carrier.

The two plants in Racine have a combined 551,271 square feet of manufacturing space and about 400 employees. The company uses a total of 21 cells, 14 of which are manufacturing cells for milling, turning, grinding, drilling, finishing and other such operations. The others are used for assembly, process completion and so forth. The company performs all operations except heat treating in-house.

The drive shafts are produced in 10 different diameters with various tapers. The shafts range from 8 to 48 inches long, with diameters ranging between 0.5 and 10 inches. The company holds tolerances between 0.0002 and 0.001 inch and surface finishes from 10 Ra to 40 Ra. Materials include 1144, C1144, 4145, 4140 and 8620 steel alloys as well as some stainless. Order quantities range from a single shaft to 500 pieces.

The company had been looking for a process change in the production of transmission shafts. Two grinders were used to grind the straight ODs, and a third was used for plunge grinding tapers. Terry Andersen, grinding team leader, programmer and machine operator, says this was a slow, operator-intensive process. Shafts had to be refixtured from the OD grinders to the plunge grinder. To improve productivity, the company wanted a grinder with a full B axis to combine the processes in a single machine.

When the company began searching for a flexible grinder to do shaft work in one shot, everyone was “a little leery,” Mr. Anderson says. There weren’t many manufacturers to choose from, and certain shaft dimensions eliminated some right away. At one point, the company actually acquired a grinder with a full B axis. However, the machine wouldn’t hold diameter size or taper tolerance and was not consistent, leading the company to continue with the old method.

“There was another company that was just coming out with a full B-axis machine, and they maintained they could accommodate our specs, tolerances, surface requirements and shaft dimensions, but we decided against it,” Mr. Anderson says. “This was going to be their first machine of this type, and frankly, no one wants to be anyone’s guinea pig—especially when you couple this with our previous experience.”

Eventually, the company settled on the Kellenberger Kel-Varia cylindrical grinding system with the Heidenhain GRINDplusIT control. A key factor in the company’s acquisition of the machine was its ability to hold tight tolerances while grinding tapers. On many shafts, the taper is nothing more than a press fit. Most of the tapers’ surface requirements are 40 Ra, but some have an angle of 30 to 1, which is less than a 1-degree taper.

“We had to have a machine that could handle that kind of range of demand,” Mr. Anderson says. “It had to be flexible, agile, rigid, and above all, repeatably consistent in holding very tight tolerances.”

The machine’s hydrostatic guideways are designed to provide accuracy and avoid friction and stick-slip movement. It features absolute measuring in the B axis, incremental, distance-coded scales in the X and Y axes and a high-resolution C axis. The grinder can also be equipped with a second B axis for more dimensional stability and profile accuracy.

The B axis permits automatic positioning of the wheelhead at any angle. For positioning accuracy, it includes a precision worm gear and distortion-free clamping. A Hirth coupling, which indexes at 2.5 degrees, also contributes to positioning accuracy. The Kel-Set automatic grinding wheel measurement system enables automatic movements to the measuring ball and to the grinding system, and it stores position information to the control system. When swiveling the wheelhead into any angle, the system automatically accounts for the positions of the wheel edges. In addition, the option of interpolating the X and C axes allows grinding of non-round shapes such as polygons, free contours and eccentric forms. For various types of grinding operations, the machine can use universal, diagonal and tandem-type wheelheads.

The grinder’s Heidenhain control features a Windows 2000 operating system, a graphics editor, expanded grinding cycles, intermediate dressing at the push of a button, comprehensive tool management, several reference points for each grinding wheel, remaining-travel display and more.

“The Kellenberger not only met all our requirements, but it was a proven machine, so we didn’t have to worry about working the bugs out of a new design,” Mr. Anderson says. “It’s been very reliable, and most important, it holds tolerances and surface finishes with remarkable repeatability.”

Because the company runs as many as 1,200 different shafts, change-over and setup are very common. However, according to Mr. Anderson, the new grinder makes this easy.

“Depending on what’s involved, we can changeover from shaft to shaft in about 10 minutes, especially if we’re not changing centers, and it’s strictly a matter of moving the tailstock and changing the driver,” Mr. Anderson says. “If you need to change centers and drivers, then you may be up and grinding in 20 minutes or less.”

About a year after purchasing the first Kellenberger, Twin Disc bought a second. With the exception of a hydraulic tailstock to handle even heavier shaft work, the second machine is identical to the first. The two machines reside in a single cell, and one operator runs both.

“We’re able to run twice as much product as before,” says Gary Pope, plant manager. “One operator does two shafts at once, and they come off finished. We run these machines 6 days a week, 24 hours a day, and we’ve already seen improvements in productivity. The accuracy and repeatability couldn’t be better.”
http://www.mmsonline.com/articles/flexible-grinder-streamlines-drive-shaft-production.aspx

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Meeting customer demand for both quality components and consistent, on-time delivery is essential for any shop’s competitiveness. However, having to subcontract work that can’t be done in-house can add weeks or months to delivery times and compromise quality standards. This was the issue faced by Weldall Manufacturing, a company specializing in medium- and large-sized fabrications. Driven by frustration over lack of control and mounting customer demand for complete fabrications, Weldall added CNC machining to its welding, plasma cutting and forming capabilities in 1993. The same factors recently drove the company to purchase its first vertical turning center, a Giddings & Lewis VTC 1600.

President David Bahl Sr. founded Weldall in 1973 in a small building with rented equipment while still working a full-time job. Today, the company operates out of a 144,000-square-foot facility and employs 130 people running two shifts. Mr. Bahl attributes the company’s steady growth to an emphasis on quality and customer service, a well-trained workforce and an ongoing commitment to stay abreast of the latest technologies. Along the way, Mr. Bahl’s sons, David Jr. and Dan, joined their father in the business.

Over the years, Weldall has produced some rather large fabrications, including the first tower crane for China’s Three Gorges Dam. The company can handle parts as heavy as 100,000 pounds. Its welding technology includes flux core, hard wire, gas metal arc and submerged arc. For automated welding, the company uses automatic seam welders as well as two CNC robotic welders with horizontal travels ranging to 29 feet. A blast machine cleans both plate and structural metal, while several plasma and laser cutters perform plate cutting. A 30-foot-long, 1,375-ton press brake handles forming operations.

To avoid subbing out work, the company ventured into CNC machining with the addition of an HMC. Today, two CNC machining centers with rotational machining heads and a three-axis vertical mill sit alongside the fabricating equipment.

“Customers don’t like to have a weldment done here, then have to move it someplace else for other operations,” Mr. Bahl says. “They want to cut one purchase order and get it complete. If you can bring machining in-house, at least you can move things around to accommodate the customer.”

With this in mind, the shop purchased the Giddings & Lewis VTC 1600 to bring even more jobs in-house. According to Mr. Bahl, Certain applications simply can’t be performed on regular machining centers.

“Sometimes you can’t get into an area to mill; you have to turn it,” he says.

Weldall looked at three different dealers in its search for a vertical turning machine. Ultimately, it chose the VTC 1600, partially because of the builder’s quick delivery time, Mr. Bahl says. While the other two dealers quoted delivery times ranging between 18 and 30 months for equipment built overseas, Giddings & Lewis was able to deliver its machine in only 4 months.

The builder attributes its ability to meet this delivery time to its modular approach to machine design and production. Interchangeable modules for components such as toolchangers, tables and pallet changers reduces the time required to build machines and increases reliability, the company says. According to Mr. Bahl, this allows Weldall to interchange parts easily and ensures that new parts are almost always available.

Service was another factor that led Weldall to choose the VTC 1600. The company needed help to become acquainted with vertical turning, and a pre-installation meeting at its facility reviewed everything involved in the installation process, from the foundation, staging areas and lift equipment to the required power and fluids. After the completing the installation, the machine tool builder sent a run-off specialist to train operators and assist with programming and processing. The builder continues to assist Weldall whenever needed.

“You can’t afford to have the machine down for weeks at a time,” Mr. Bahl says. “When we call Giddings & Lewis, they’re usually down here the same day or the next day.”

The VTC features a hydrostatic ram with high dynamic stiffness and vibration damping to enable accurate, heavy cuts, the builder says. Weldall opted for a vertical live spindle attachment and a C axis, which enables plunge milling and helical interpolation. In addition to the live spindle, a 360,000-position C-axis table provides flexibility. The head is stored in the tool magazine for easy head changes. The company also opted to purchase a right-angle head for the live spindle to perform operations on the outside of the part. Full X-axis travel left and right of center enables cutting on both sides of the center. In addition, this feature permits probing in diameters rather than radii.

One example of a new part made possible by the addition of vertical turning is a wastewater pump. Mr. Bahl says the component was impossible to machine on anything but the VTC because the shop couldn’t get a milling cutter inside the part. The operations performed on the part include turning, boring and facing. With the live spindle, Weldall can drill, tap and mill. The live spindle’s right-angle head reduces cycle time because a second setup is not required to machine the large tap on the side of the part. Additionally, the on-machine part probe allows operators to save time on both positioning and inspection.

According to the company, vertical turning capability has made a real difference in satisfying customer demand. By giving Weldall the responsibility for the welding and machining of their projects rather than using several sources, customers can benefit from uniform quality and consistent, on-time delivery.
http://www.mmsonline.com/articles/fabricator-produces-parts-complete-with-vtc.aspx

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Coatings are typically applied on cutting tool inserts using chemical vapor deposition (CVD) or physical vapor deposition (PVD). In either case, imperfections in the coating’s outer layer can occur as a result of coating application, according to Iscar (Arlington, Texas). High heat followed by cooling during CVD can leave behind micro-sized cracks in the coating. Although PVD does not involve high heat like CVD, the PVD process can leave behind tiny droplets of coating material on an insert’s surface. These ragged surface imperfections adversely affect chip flow and insert life.

Such issues led Iscar to develop a proprietary, post-coating finishing process to improve insert surface quality. The company’s Sumo Tec finishing process smoothes any cracks in the outer TiN coating that develop during CVD and also removes droplets that PVD might leave behind. The resulting reduction in friction, heat and surface stresses is said to extend tool life and cutting performance. In addition, the process improves insert toughness and chipping resistance to reduce the chance of a built-up edge condition, the company says.

An example of the droplets inherent with the PVD coating process can be seen in the left-hand, close-up shot on this page. The right-hand image shows how the droplets have been removed via the Sumo Tec finishing process. The portions of the insert that received the finishing process are black in color.

In addition to the finishing process, Sumo Tec insert technology features a new series of tungsten carbide grades. It is used with new versions of Iscar milling, turning, drilling and parting/grooving tools. For example, the Sumomill T290 end mill family provides a number of cutting edges on a small tool diameter to enable increased feed rates and high metal removal rates. The tangentially helical inserts are clamped on the periphery of the tool body. The resulting large tool body core is said to provide high torsion resistance.

The expanded Heliturn LD family of turning tools uses helical inserts designed with highly positive, radial cutting edges and positive rake angles. This combination results in reduced cutting forces. A new lever-clamping tool design facilitates chip flow, particularly when performing longitudinal turning, undercutting and round profiling.

Iscar’s Sumodrill line uses adjustable, replaceable cartridges to perform rough drilling operations ranging in diameter from 61 mm to 80 mm. Spacers of varying thicknesses can be used to bring the interchangeable tool cartridges to the required diameter.

The Tang-Grip line of parting tools also has a tangential insert design. The single-ended insert can perform parting, grooving and interrupted grooving operations. Tang-Grip tools have a tangentially oriented insert pocket to allow parting at high feed rates. The tool have no upper clamp to improve chip flow and reduced the likelihood that streaming chips will damage the tool body. These tools have been designed so that the insert won’t pull away from the tool body during retraction.
http://www.mmsonline.com/articles/smoothing-insert-surfaces-extends-tool-life.aspx

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A new multitasking machine from Mazak Corp. (Florence, Kentucky) addresses one of the drawbacks that some shops find with this ever-more-popular type of machine tool. Many of these machines require a large amount of floor space even though the workpieces are relatively small. Shops with limited space may have difficulty accommodating these seemingly oversized machines on the shop floor. The Integrex i-150 Multi-Tasking Center, however, has a small footprint. The base of the machine sits within a 58-square-foot area.

Clearly, machine tool platforms that combine milling and turning capability are a boon for shops looking for a reliable means to complete a part in one setup. Essentially, one such machine does the work of two. Because many designs for multitasking machines include a second spindle, their space requirements are proportionately larger. The i-150, which provides done-in-one processing of small, complex workpieces, does without this second spindle. According to the builder, it is ideal for medical appliances and high-precision component machining that involves round, square or angular features. The machine can accommodate bar stock as large as 2.56 inches in diameter.

It uses a swing-away workholding device instead of a second spindle, thus making structural provisions for this spindle unnecessary. A typical scenario for done-in-one processing on the i-150 starts with the workpiece automatically feeding into the main, 15-hp horizontal spindle. When operations on the front side of the workpiece are completed, the workholding device swings up to clamp it, as shown in Figure 1. After cutoff, the device swings down 45 or 90 degrees with the workpiece in its grip. Repositioning the 10-hp, 12,000-rpm milling spindle in the B axis enables machining on the back face of the workpiece (Figure 2). The workholding device does not turn the workpiece, but circular interpolation of the milling head provides a substitute. Y-axis travel extends ±3.94 inches (±100 mm) from the center line to provide the milling spindle with the range and flexibility for this function. When the workpiece is unloaded, the workholding device swings out of the way to clear the machining zone. The device can also act as an NC tailstock in its upright position.

Another way this machine saves space is by providing a front-loading tool magazine. This puts tools close to the ATC and eliminates the need for side or rear access to the magazine. The machine comes standard with a 36-tool magazine. The large number of tools makes it possible to run many part types in short batches or in a sequential series, to produce a ready-to-assemble kit without restocking the magazine. A 72-tool version is also available.
http://www.mmsonline.com/articles/multitasking-with-a-small-footprint.aspx

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Shops typically create workpiece blanks from barstock by using cutoff saws or circular saws. These sawing processes create burrs on blank ends and cause material loss due to the kerf. Blanks might also be created by shearing, but this can cause cracking or other damage to the ends of the blanks.

High-velocity impact cutoff, also known as adiabatic cutting, is an alternative cutoff process for high-production machining applications. In theory, adiabatic cutting uses kinetic energy to create a shockwave of sorts that softens a narrow, vertical plane through the material (known as the adiabatic zone). The energy is converted into heat faster than the material being cut can dissipate it, and this controlled plastic deformation separates the material.

In practice, the energy is provided by a mechanical, pneumatic or hydraulic press using precise dies that create the adiabatic zone and separate the material. There is minimal work hardening and the resulting blanks have accurate lengths as well as edges that are burr-free and perpendicular. High Velocity Impact Technologies (HVIT) offers adiabatic cutoff systems using Hydropulsor hydraulic presses. HVIT, located in DeKalb, Illinois, provides individual presses or turnkey cutoff systems that include material handling and straightening components for coils. These systems can accommodate material ranging from 3-mm-diameter wire to barstock measuring 70 mm in diameter.

Within the press is a set of closed dies (one stationary and one moveable) with holes typically 0.003 inch larger than the material’s diameter. Adjustable with the hydraulic press, the speed at which the moveable die travels in delivering the ram’s energy to the material is set according to material hardness and barstock cross-sectional area. The perpendicularity of the blank ends can be controlled by machining the appropriate relief angle in the faces of the mating dies. Adiabatic cutoff is performed without coolant and can be used to create blanks from metals ranging from bearing and high speed steels to hardened aluminum, brass and copper.

To get a sense of the material savings that adiabatic cutoff offers, consider a bar that is 6 meters long and 70 mm in diameter. Cutting 150-mm blanks from this bar with a 5.5-mm-thick blade would produce 220 mm of scrap in the form of kerf (almost 1.5 blanks) for every bar. Sawing processes also have additional costs in terms of coolant and blades.
http://www.mmsonline.com/articles/creating-workpiece-blanks-via-adiabatic-cutoff.aspx

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Many companies use one operator to run more than one CNC machine. Indeed, I’d bet the majority of companies in the United States use at least some of their operators in this manner.

Several factors contribute to the wisdom of having one operator run two or more CNC machines. Some of the most important considerations include lot sizes; cycle times; setup times; machine costs versus operator costs; urgency of getting jobs done; and even availability of skilled operators in your area

In many cases, I disagree with the decision to use one operator to run multiple machines—at least from a cost standpoint. I’ve been in many companies in which using operators in this fashion actually costs more than having a separate operator run each machine.

I suspect that at least part of the reason some companies have one operator running multiple machines is that management just can’t stand to see someone idle. While this may be an important concern, a hasty decision to have one operator run multiple machines often results in much lower overall machine output. Again, this may cost more than having a separate operator run each machine.

My discussions will be limited to comparing costs from having a separate operator for each machine, as opposed to one operator for two machines. This means, of course, that you must know your costs. The only costs in this equation are machine cost and operator cost.

Machine Cost
For this purpose, machine cost is the hourly rate a company pays to use the machine (not the cost your company charges for the machine’s use). At the very least, it is the monthly payment a company makes (loan/lease) divided by the number of hours per month the machine is in use.

There is usually much more involved with determining machine cost than just the monthly payment. Cost of upkeep, which includes preventive maintenance, lubricants, coolant and even crash repair, should be included in your machine-cost calculation. Some companies also include the cost of floor space the machine requires.

Note that I’m not including tooling of any kind in the machine cost. We need only the amount of money your company must pay per hour for the machine’s use. (By the way, if no one in your company can tell you the cost of each machine, find out why.) Machine cost should be an important factor in determining the amount of profit your company makes for each job you do or the product you sell.

For accounting purposes, some companies apply a blanket rate to the machines they own. For these companies, every machine the company owns—be it a $5,000 knee mill or a $200,000 CNC machine—has the same cost per hour. This may be good for approximating purposes, but it won’t be accurate enough for making wise decisions related to operator utilization.

Operator Cost
Again, we’re looking for a cost per hour. This cost will, of course, include the operator’s wages. But like machine cost, there is more involved with determining operator cost. All benefits the operator receives (insurance, employment taxes and retirement-fund contributions) are among the costs you must consider.

It is not unusual for the total of all benefits to equal or exceed the operator’s hourly wage. For our examples, we’ll simply double the operator’s hourly wage for the operator cost.

A Quick Comparison
The more the operator’s cost, the more advantageous it will be to have one operator run two or more machines. The more each machine’s cost, the less advantageous it will be to have one operator run two or more machines.

In many companies I’ve visited, a manager can point out every penny that goes into what an operator costs (again, wages plus benefits). One company I visited even includes the cost of the parking space the operator uses to park his or her car. However, when it comes to machine costs, they are not nearly so knowledgeable and diligent. Again, having an accurate value for both operator and machine cost is of paramount importance to making wise operator-utilization decisions. Inflated operator costs and/or devalued machine costs lead to poor operator-utilization decisions. It will appear that using one operator for two or more machines is more cost-effective than it really is.

Though I may be getting ahead of myself a bit, note that the maximum cost benefit you can expect per hour is the cost of one operator. Think about it. When you have one operator running two machines instead of a separate operator for each machine, the most you can gain per hour is the hourly cost of one operator.
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James Wilton gets to combine his talent for machining with his love of guitars at Coast Precision CNC. Mr. Wilton, who has 15 years of machining experience, opened his two-man shop in Richmond, British Columbia, in November, 2006. Although he caters to a wide variety of jobs, including aerospace tooling, nautical components and aftermarket automotive parts, arguably his most “flashy” work is machining aluminum guitar bodies and other components for the upstart Liquid Metal Guitars company (www.liquidmetalguitars.com).

Instead of being carved from traditional hardwood, these contoured guitar bodies are machined from billet 6061-T6 on an VF-3 vertical machining center (VMC) from Haas Automation (Oxnard, California). The VMC is the shop’s first CNC machine tool. Mr. Wilton, a third-generation machinist, wanted a machine that was not only capable and affordable, but also offered the flexibility to go after a range of machining work. Machine service and support was just as important, especially considering that it is the shop’s only CNC machine.

The VMC has X-, Y- and Z-axis travels of 40 by 20 by 25 inches, and each axis has a rapid traverse rate of 1,000 ipm. The 40-taper machine was specified so that it would be both versatile and relatively easy to operate, even for employees with limited experience. Options include a side-mount toolchanger with 24 tool positions, Renishaw probing and a two-speed gear box. The two-speed gear box provides the machine with the torque required for heavy cutting (250 foot-pounds at 450 rpm) in addition to 10,000-rpm spindle speed when needed. Thus far, the shop has machined materials ranging from plastics to 316 stainless steel. The VMC also has fourth-axis wiring and drive in case the shop decides to add a brushless-type rotary table and pursue four-axis machining work.

Probing capability and the machine’s visual quick code (VQC) programming system make it easy for operators to pick up workpiece zeros and measure for cutting tool offsets, Mr. Wilton says. After an operator installs tools in the toolchanger and identifies the tools to be measured for a job, the machine automatically performs all the tool measurements. This frees the operator to set up new jobs or perform other duties. According to Mr. Wilton, the Haas service representative was helpful in assisting the shop in writing macros for measuring for offsets.

Mr. Wilton began working with Liquid Metal Guitars approximately two months after his shop opened. The shop that the guitar company had first approached to machine the guitar bodies wasn’t helpful in terms of making small changes to the original model. That forced the company to continually pay the engineering firm that created the original CAD model to make the small changes. When the guitar company met Mr. Wilton and took note of his appreciation for guitars, machining experience and willingness to make small design changes, it decided to give the work to Coast Precision CNC.

The guitar body was designed in SolidWorks, and tool paths were created using OneCNC, which accepts native SolidWorks files. The first steps in machining the contoured guitar body is skimming the top face of the billet aluminum and drilling clamping holes. Next, the workpiece is flipped so that the backside cavity with stand-offs can be machined (see top image on left). This brings the wall thickness to 0.125 inch.

The body is flipped again to lightly machine the topside radius in addition to the holes for the pickups and electronic controls. Then, the angled neck pocket is created using a dedicated jig. Finally, the body is fixtured to an angle plate to cut the hole for the 0.25-inch cord jack.

The backside cover is machined from 0.125-inch aluminum sheet. Mr. Wilton currently uses a dedicated fixture for the covers, but plans to use a vacuum workholding table as soon as guitar sales take off and the volume of machining work increases. The truss rod cover (a small plate at the top of the guitar neck that is typically made of plastic) is also machined from aluminum sheet. At first, these were fixtured with double-sided tape and machined using very small depths of cut. Now, Mr. Wilton uses a custom fixture that allows him to machine six pieces in one setup faster than he could machine one piece with the original method. He notes that the scrap rate is much lower, too.

Mr. Wilton says he still has a few ideas up his sleeve to speed part change-over and cycle time. He’s also experimenting with different guitar body finishes. It is much easier for the guitar company to communicate to Mr. Wilton the type of look it desires because both parties are knowledgeable about guitars and guitar design. He hopes the exposure that the shop will gain as Liquid Metal Guitars establishes itself in music circles will be parlayed into additional guitar work from other companies. Mr. Wilton also plans to design and machine billet guitar components that have traditionally been castings, such as bridges. He may also soon add a two-axis CNC lathe to complement the shop’s milling capabilities.

Mr. Wilton grooves on this work because he likes machining and loves guitars. To him, combining the two is magic—it brings out the best of the machinist that’s inside.

http://www.mmsonline.com/articles/start-up-shop-makes-splash-machining-aluminum-guitars.aspx

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Peering at the shiny NT4250 DCG situated on Mori Seiki distributor J&H Machine Tools, Inc.’s shop floor, Imo Pump realized that it would need to make some savvy toolholding choices to assume ownership of the nicely equipped mill-turn center. The pump manufacturer had reached a pivotal point in production of a certain screw. In fact, what was called for was a complete overhaul of the current machining process. Capable of turning and milling in one setup, the mill-turn machine could consolidate multiple setups and thus enable the company to streamline screw production. However, implementing the revamped process would hinge on identifying the proper tooling to complement the machine’s ample capabilities.

The Monroe, North Carolina-based shop says its first order of business was to identify a way to hold the tool securely enough during a rough slotting operation, an integral part of the machining sequence. Otherwise, it would not have adequate means to abate vibration and decrease cycle time. Thus, it would not have a way to justify the expense of acquiring the NT machine.

“Initially, we were rough milling these screws using a totally different method,” explains Jonathan Hunter, manufacturing engineer at Imo Pump. “We were using numerous machines to carry out what we can now accomplish with one. Between turning operations, milling keyways and milling threads, I suppose that we’ve been able to eliminate five different setups.”

Ultimately, the shop chose to apply a milling chuck to a distinct spindle interface, a Capto C6 to be exact, to reach higher cutting efficiencies, accelerating cycle times by between 15 to 20 percent.

The particular component is a power rotor screw to be implanted in one of the many screw-type pumps of varying shapes and sizes conceived and manufactured at Imo Pump. Predicated on engineering principles set in place by founders Carl Montelius and Bengt Ingestrom in 1931, Imo Pump is now a division of Colfax Corporation. Credited with the design of the first multiple-screw pump, the company says its rich history of invention continues today, as it produces pumps that operate quietly at high speeds and high pressures in thousands of applications. The manufacturer attributes the widespread use of its pumps to the simplicity of the design. Its products can be found in barges and ships and in engine rooms on commercial marine vessels and combat ships, to name a few.

Commonly made of 4140 steel, the power rotor screw is turned by the motor and drives two idler screws in the low-pulsation pump. Because this screw ensures the smooth operation of the three-screw pump, it is imperative that the shop machine it accurately on a consistent basis. In order to do that, Imo Pump would need to remedy a vexing process segment—a rough slotting operation. The operation involved rough milling the screw threads using a 3/4-inch, four-flute carbide end mill.

“This roughing of the slot, which is a key area of the part itself, was really the driver to make or break the entire process,” comments Jack Burley, VP at Big Kaiser.
The Matter With Chatter

Thus far, the company had not been able to hold the carbide end mill rigidly enough to make the required depth of cut (DOC) and achieve the high speeds necessary to rough mill the threads expeditiously. Realizing that inadequate clamping forces could potentially cause rough finishes, frequent tool breakage and workpiece marring, Imo Pump began a series of trials.

J&H Machine Tools, Inc. performed all of the testing at its Charlotte, North Carolina facility. Over the course of the trials, various seemingly plausible options proved impractical, given the cycle time and concentricity constraints.

For instance, both an end mill holder and an ER collet chuck posed limitations. For this applicaiton, both lacked the characteristics needed to provide the necessary rigidity, which meant running the part slower.

“During roughing, the ER collet chuck was actually pulling the tool out of the holder, making it cut undersize,” Mr. Hunter explains. “The standard end mill holder imposed extra forces on the tool itself. I noticed extra wear on tool while holding in that style. The excessive vibration caused stresses that receded the end mill.

“With this collet style, we could only achieve about half the depth of cut,” he adds. “In addition, we were running slower, and the collet seemed to be marring the workpiece.”
The Right Connection

After weeks of trial runs that failed to meet the predefined operating parameters, the team was open to suggestions. It consulted Richard Bevers, regional manager for Big Kaiser. One facet of the shop’s selection criteria was compatibility with the Capto C6 spindle interface.

As Mr. Burley explains, the Capto C6 interface already provides a foundation for rigidity, which can be enhanced with the appropriate application-specific toolholding.

“This spindle interface consists of a tri-lobed tapered male connection so that when you put it into a receiver there is no drive key per se,” Mr. Burley explains. “The polygon shape is the drive system. Because it is on a slight taper, it precisely locates into a spindle.”

As a licensed manufacturer of Coromant Capto tooling systems, Big Kaiser offers numerous toolholding systems that are compatible with spindles equipped with a Capto interface. After reviewing the application, Mr. Bevers determined that the Mega Double Power milling chuck could potentially rectify chatter issues associated with the other two holders. Supplied from stock, the tool was placed into operation immediately. With the vibration issues remedied, Imo Pump was consequently able to increase the DOC as well as the feeds and speeds.
Better Concentricity

According to the manufacturer, the rigidity of the holder itself and how it clamps on the tool eliminates the vibration. Its locking nut configuration enables the chuck to offer accuracy of 0.0002 inch at four times the diameter, which translates to constant cutting for all flutes engaged in the workpiece.

Rigid clamping begins with the outer diameter of the toolholder, which is said to be completely symmetrical. To tighten the tool in place, the operator need only turn this nut in a clockwise direction with a custom wrench, dubbed the Mega wrench. This wrench fits over the diameter and works as a one-way clutch. It grips the smooth OD without marring or causing indentations on the clamping nut. When the nut is fully tightened, there is double contact between the toolholder body and the nut itself.

“This milling chuck has high gripping force, probably in the order of seven to ten times more than what one might find with a collet chuck,” Mr. Burley says. “It offers excellent runout and higher mass and damping capability when compared to an end mill holder.”

These capabilities, Mr. Burley says, can be attributed to larger mass at the cut (where the tool goes into it) and the construction of how the tool is clamped is so much more rigid, the damping capability of the tool results in smoother cutting.

Mr. Burley approximates that Imo Pump has realized three times more DOC and three times faster feed rate with this tooling solution, compared with the ER collet and the standard end mill holder.

Big Kaiser’s Double Shot (DS) configuration also contributes to noticeable gains in cutting efficiencies at Imo. A standard feature of all Big Kaiser toolholders, this peripheral cooling system propels coolant through the holder, right along the edge of the end mill.

“The body of the toolholder contains holes to allow coolant to pass through,” Mr. Burley explains. “This not only flushes chips but also cools the cutting edge.”

Since May 2007, the mill-turn has resided at Imo Pump’s Monroe facility. Coupling its capabilities with the attributes of the new milling chuck has been instrumental in streamlining screw production. The company cites a setup reduction of 35 percent (on average), in addition to favorable tooling life and discernable leaps in productivity.

“We’ve noticed better life on that particular tool, and we just added another chuck,” Mr. Hunter concludes.

By all accounts, the toolholding itself, though initially more expensive than other options, is earning its keep.

“The tooling has been crucial in delivering a marked improvement in productivity,” Mr. Bevers concludes. “In the long run, those kinds of results are more valuable than saving a few bucks on a toolholder.”

http://www.mmsonline.com/articles/milling-chuck-pumps-up-productivity.aspx

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Machining castings into precision components can be quite a challenge. In addition to traditional machining and handling issues, global competition can put pressure on shops to keep prices down. Faced with these issues, TMF Center, a Williamsport, Indiana-based manufacturer of components for the construction equipment and trucking industries, developed a long-term strategy for using automation to develop and manufacture tight-tolerance parts and achieve aggressive cost targets.

With 260 employees and two plants, TMF manufactures machined fabrications, precision parts, machined flat barstock and machined steel and ductile iron castings for the heavy OEM market. One job required machining a cast variable valve actuator for a highway truck engine on all six surfaces from many angles. To avoid multiple setups that could increase part variability, the shop used standalone, five-axis Mazak Variaxis 630 machining centers from Shelton Machinery that enabled a three-step machining process.

The first operation machined locating details and rough features on the cast part. The second operation machined all topside surfaces before the part was flipped for the third operation and final machining. As production grew, the company installed a Mazak Palletech flexible manufacturing system (FMS) to minimize labor content and achieve production schedules.

First-generation machining and second-generation prototyping was achieved simultaneously on the initial line. However, the second-generation design, a combination of the variable valve actuator and an engine brake, was more complicated. The newly designed part required more extensive machining and a higher production volume, prompting the company to purchase an additional FMS Shuttle System as well as more machining centers.

Still, despite hitting production goals with tooling refinement, hard work and manual operations, the shop couldn’t meet customer cost goals. Because the new design incorporated performance benefits and cost savings, customer demand mandated a quick transition period. Further automation was required, and that automation had to work with the existing systems.

So, the company purchased a Fanuc Robotics M710iBT Toploader robot to service its FMS. With travel length of 26.5 meters and a 70-kilogram payload, the robot could traverse the distance across the machining lines to deliver parts. The robot’s wrist could flip parts over between the second and third operations, and its six axes could tolerate any out-of-alignment or out-of-square conditions of the FMS.

In addition to the robot, the company purchased a custom hydraulic clamping system that could couple and decouple to the FMS pallet. Designed and delivered by Busche Engineered Tool Division, the hydraulic clamping system allowed more automation and greater process repeatability than the original FMS’s manual nut drive system. Fanuc Robotics engineers worked with Busche engineers to develop an interface between the robot, the automatic clamping and the Mazak FMS.

TMF Center also worked with Fanuc engineers to define a post-machining deburring process. A floor-mounted Fanuc Robotics R2000iA robot manipulates the part around a stationary carbide deburring cutter to eliminate large burrs from the finished parts. Barry Henderson, Fanuc Robotics controls engineer, used the robot’s Remote Tool Center Point function to allow easier teaching of the deburr and blow-out positions. Fine burrs are removed later in the process by a thermal deburr machine.

The thermal deburr process helped in that the smaller burrs did not have to be removed by the robot. However, it also complicated things in that any loose chips on the part or in the part had to be removed. Loose chips often became dislodged and fused to the casting, creating a scrap component. Thus, operators had to probe and blow out all the part’s holes and cavities. To mimic this manual approach, Fanuc and TMF Center developed a compliant air-pipe hole-blowout system to force out embedded chips through air pressure.

The overall process works like this:

* Operators manually load the part onto a Mazak Variaxes 630 machining center for the first operation, which consists of the rough machining of locating surfaces on the raw casting. Operators then load the part onto a conveyor for the infeed to the Fanuc M710iBT Toploader robot.
* The robot uses a dual hand tool to pick up the part and load it onto a staging station near the FMS shuttle for line 1 or line 2.
* The robot interfaces to the hydraulic clamping system to load and unload the part for the second and third operations. After the third operation, the robot transfers the part to an outfeed conveyor.
* A Fanuc R2000iA robot removes the part from the outfeed conveyor and uses a carbide deburr tool to eliminate large burrs. It then probes the openings on the part and blasts out embedded chips. Finally, the robot marks each part for time, date and machining operations to allow traceability and quality tracking by both TMF Center and the customer.
* The robot places the part back onto the outfeed conveyor for manual unload and inspection prior to thermal deburr and washing operations.

The combination of a toploader guarding solution and the FMS loader system allows the company to service or maintain any of the machines or the loader while still running the balance of the system. The system can achieve high production and machine utilization rates while supporting tool setup functions, the company says.

This full automation solution has been installed and running since late 2005. The company says it has produced an incremental reduction in scrap and a reduction in labor costs that have paid back the automation investment two-fold.

http://www.mmsonline.com/articles/flexible-automation-process-helps-shop-reduce-costs.aspx

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A different breed of turn-mill machine was recently introduced at EMO 2007 in Hannover. The UniCen 504 from Monforts combines turning and four-axis milling with integral laser hardening and laser welding in one workpiece setup. The machine platform enables shops to bring often-outsourced laser treatment in-house to reduce lead times, allow better control over secondary laser operations and offer improved flexibility to respond to changing customer needs.

The multipurpose UniCen machine, which is currently available in the United States from Sunbelt Machine, Inc., is the result of a German Federal Department of Education and Research (BMBF) project. It was developed by Monforts (Monchengladbach, Germany) in cooperation with partners including the Fraunhofer Institute for Production Technology, Laserline GmbH, Precitec KG, EXAPT GmbH and Sempell AG.

The turn-mill machine can accept workpieces as long as 900 mm and offers maximum swing diameter over bed of 600 mm. In addition to its turning turret, the UniCen has a 12,000-rpm, B-axis spindle that provides ± 95 degrees of rotation for milling and drilling operations. The turn-mill’s two modular laser units—one for hardening and the other for welding—each install via HSK 63 interface into the B-axis spindle. This allows the laser units to be automatically removed from the spindle and stored outside the machining environment, protecting sensitive optical components from damage by coolant and chips during turning and milling operations.

The laser welding unit can perform deposit welding and alloying at specific areas of a workpiece. This is often done to repair worn or damaged components—weld material is added and then the workpiece feature is machined back to original specifications. The coating unit contains the optics to form and guide the laser beam in addition to a welding wire feeder and a process sensor. A coaxial gas supply protects the focusing lens against contamination during the welding process. Laser-deposit welding is said to cause virtually no workpiece distortion, as the localized absorption of laser energy causes minimal heat induction.

The laser hardening unit performs case hardening of specific workpiece features that will encounter wear due to mating components, such as bearing journals, keyways and splines. The maximum hardening depth is 1.5 mm with almost no workpiece distortion. The unit can generate a variable laser spot as large as 20 mm by 50 mm on the workpiece. This is appropriate for quenched and tempered steel, cold- and hot-forming steel, high-speed steel, stainless steel and cast iron.

The machine’s high-power diode laser source delivers a beam through a guiding system to each laser unit. All the laser and machining processes are controlled by the machine’s central control system. The control units for the laser equipment are connected via a profibus interface to the machine’s control. The machine control includes a CAD/CAM module that offers an intuitive, user-friendly interface for programming multiple operations.

http://www.mmsonline.com/articles/turn-mill-and-laser-harden-in-one-setup.aspx

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