Shop Solutions: Guitar Maker Tunes Up With Metalcutting
C.F. Martin and Co. Inc. (Nazareth, PA), is a world-famous guitar manufacturer, better known by its Martin Guitar brand name.
With 175 years of history behind it, Martin Guitar has long been the acoustic guitar of choice for some of the world's most renowned musicians. Elvis, Eric Clapton, Johnny Cash, Tom Petty, Willie Nelson, Sting, Jimmy Buffet, and Paul Simon are just a few of the legendary guitarists who made music history on a Martin. The company's influence continues today, with prominent artists such as Beck, Dave Matthews, John Mayer, and Jonny Lang relying on the quality of Martin guitars to convey their music to the world.
Above all, Martin's success has stemmed from a total commitment to quality. The company treats its manufacturing processes as an art form, with many manual operations requiring employees to spend years mastering and perfecting. Any change in production processes is undertaken with the utmost caution.
Manufacturing solutions can end up providing substantial benefits well outside the scope of application for which they were originally developed. In just one such case, Martin Guitar, found that technological innovations created by GF AgieCharmilles (Lincolnshire, IL) for metalcutting were perfectly well-suited to boosting productivity in woodworking for its guitars.
"We will not sell a guitar unless we are absolutely sure that it meets our quality requirements," says Fred Walters, engineering project manager at Martin Guitar. "We view our reputation as being on the line with every guitar we make, so there's no room for compromise. This means our production processes have to be as close to perfect as possible, as we simply do not allow the production or sale of any second-quality guitars," Walters explains.
Different woods produce levels of sound quality that vary dramatically in guitars. The tonal woods that offer the best-sounding results are in increasingly short supply, quite costly to acquire, and are not to be wasted or scrapped. While most manufacturers avoid the production of seconds for obvious reasons, Martin Guitar is especially mindful of it.
This makes Walters' job extremely challenging. As engineering project manager, his responsibilities include identifying potential new processes and meticulously evaluating whether they can be successfully integrated without affecting the quality of the finished product. Typically, processes requiring extensive physical labor receive the most attention, as they tend to be the most time-consuming and can be exhausting for employees.
Looking to streamline its manufacturing, Martin Guitar discovered significant inefficiency in the method for installing frets on a guitar's neck. Fret slots have to be cut all the way across, from one end of the fingerboard to the other. The metal fret was then installed and trimmed to be flush with the guitar's neck. This would leave an opening under the fret, between the metal and wood, that would have to be hand-filled with glue, which then required 24 hr of drying time. Finally, excess glue was removed by hand, to achieve a smooth, unbroken surface along the edge of the neck.
"The process created somewhat of a bottleneck in our fretting operation," says Walters. "In evaluating the process, we knew that pocketed fret slots would allow us to produce the same quality of our guitar neck or possibly improve it, without the manual application of glue and associated waiting time for drying. Unfortunately, we hadn't found a viable solution for machining the pockets."
Pocketed fret slots needed to be 0.135" (3.4-mm) deep and just 0.022" (0.56-mm) wide. Martin Guitar possessed several VMCs with a maximum spindle speed of 15,000 rpm that could produce the pockets, but they required 69 sec per slot. That added up to 23 min to finish one board. Also, the diameter-to-depth ratio resulted in unreliable tool performance with frequent failure. Realizing that its machines lacked the levels of performance needed to update the process, the company contacted Holco Inc. (Ambler, PA), its distributor for production and inspection equipment.
The solution suggested by Holco was a Mikron HSM 800 from GFAgie Charmilles. The machine's high-speed spindle operates at a maximum of 42,000 rpm. Coupled with high feed rates, the HSM 800 provides the required levels of performance needed to cut the pockets without snapping tools. Martin Guitar provided sample materials for test cuts, and found that the results were favorable enough to justify ordering the machine.
After installing the HSM 800, Martin Guitar worked to optimize cutting speeds and feeds. Depending on the specific material being machined, cutting speeds vary between 30,000 and 38,000 rpm, and feed rates of 325–475 ipm (8.25–12 m/min) are used. While it would take 23 min to machine a single board on the old machining centers, the HSM 800 can machine pocketed fret slots in just 9.6 sec each, translating to 3 min 5 sec per board, a reduction of about 87% in machining time. In addition, with the elimination of runout, tool life was increased and the process achieved the level of stability needed to eliminate the chances of producing scrap.
"By finding a reliable way to produce pocketed fret slots, we've been able to do away with the gluing process required by the old way of installing frets," says Walters. "In addition to removing a bottleneck from production, it has resulted in significant cost savings. Also, with the pocketed fret slot we no longer have the through-slot showing on the edge of the fingerboard, so the look and feel of the neck are improved as well. While the innovations we're using were developed for shops working with metal, they have really improved our operations."
To get even more out of its investment, Martin Guitar has started using the HSM 800 for the pearl inlays on its guitar fingerboards, bridges, and head-plates. Taking advantage of the machine's high precision, Martin cuts both wood and pearl to ensure that the two pieces fit together seamlessly. Accuracy is extremely important to the application, as even a slight mismatch means that the parts will not fit together correctly.
"We're constantly looking for other ways to take advantage of the capabilities of the Mikron machine," says Walters. "It's cutting edge technology, and we'll always look for unique ways to apply it."
Tool Inspection Is A Big Saver
Dura-Mill Inc. (Malta, NY) is a manufacturer of the Whispercut line of carbide end mills. Designed with a variable helix with three, four, or five flutes to reduce chatter and noise, the end mills are especially valued by medical, automotive, and aerospace users because of their smooth operation and long life.
For cutting-tool manufacturers such as Dura-Mill, there is continual pressure to improve production quality and throughput to remain competitive. When Dura-Mill's plant engineer Charles Ward saw a genius 3 inspection machine at a Zoller Inc. (Ann Arbor, MI) open house, he immediately recognized the potential benefits for his production operations.
The sophisticated geometry of Dura-Mill's cutting tools presents many different features that must be measured to ensure tool functionality. The genius 3 machine permits fully automatic tool measurement and is claimed to allow inspection of virtually every tool parameter.
"We needed to verify step tools, taper tools, core depth, hook, gash and rake angles, primary and secondary angles, margin widths, chisel angles, k-lands, chamfers, profile in a form tool, among others," explains Ed Wuntsch, Dura-Mill's quality control manager.
"It's important that we hold our tolerances very tightly so our customers can count on machining accuracy from our tools. Because the industry lacks definitive standards for cutting tools, the difference between 'good' and 'better' tools is in the control of the tool-grinding process," Wuntsch explains.
Dura-Mill selected the five-axis CNC universal genius 3 inspection machine, which measures rake, relief, and flute angles to microns in 2-D or 3-D using digital image processing. Its positioning accuracy is 0.001 mm on the linear axis and 0.01° in the B axis. With a measuring range of 600 mm in Z, 175 mm in X, and 100 mm in the Y axis, the genius 3 is completely enclosed, dimensionally stable, and designed to reduce vibration.
For 2-D measuring, the genius 3 uses a camera with a telecentric lens and 50x magnification plus image processing software with fully automatic cutting-edge-shape detection that lets Dura-Mill measure any of its tools and cutting edges.
An incident-light measuring technique checks effective cutting-edge angle and tool orthogonal clearance angle at the cutting edge as well as other parameters. A CNC-positioned camera with a 200x magnification and segmented controlled incident light is used for such 3-D measurements.
Keeping track of production quality avoids missteps and wasted time in Dura-Mill's tool-grinding processes. Inspecting tools off-machine supports uptime during production. No time is wasted inspecting tools on-machine so the CNC grinders can run continuously.
Wuntsch does most of the setup on the genius 3 machine for inspection of each different Dura-Mill tool, and considers it to be an easy task. Grinding machine operators can access the Zoller inspection program for tools and place them correctly in the chuck. The inspection routine is automatic and, depending on the tool requires 10–20 min.
The Zoller genius 3 automatically inspects parameters important to any specific tool, such as blend points of radii, reliefs, lands, and more, so the toolmaker knows that the design is followed correctly. "We trust the genius 3 and adjust our grinding machines accordingly," Wuntsch says. "We are repeating better than ever now with our tools, because we verify the accuracy and near-perfect consistency of each tool."
Some tool features are very difficult to inspect. One such attribute is found on their high-performance aluminum series end mills where a circular margin that runs down the entire length of each flute must be examined. The genius 3 inspects this feature faster than any previous process.
For each inspected tool, the genius 3 generates a report and compares results to the nominal parameters for the tool. The operator uses the results to make adjustments to the grinding machine process so that production will be consistently within tolerance.
In operation only six months, the Zoller inspection machine has reduced scrap rate and inspection costs. "Besides affecting production quality, one of the biggest gains from the genius 3 has been freeing-up our machine operators from manually inspecting tools and allowing them to focus on working more effectively on setups and machine operation," Wuntsch says.
"The Zoller automatically inspects a tool in half the time it takes to do a complete manual inspection, and takes the human element out of the equation, avoiding operator interpretation. This also helps us use manpower more efficiently, as the Zoller inspection machine essentially saves us half-aman per shift, so to speak," says Wuntsch. "In addition to the time saving, the genius 3 is highly repeatable—within 2 µm concentricity. With its results, we can control our grinding much more closely and run untended confidently," he observes.
"We are seeing that it is a matter of survival for precision cutting-tool makers to be able to measure and verify that each tool they produce conforms precisely to specifications," says Alexander Zoller, vice president, Zoller Inc. "With the Zoller genius 3, the manufacturer can measure the outer contour of all tools automatically and independent of the operator to ±2µm. The genius 3 can check cutting angles as well as tool orthogonal clearance angles, chamfers, flute depths, and spacing automatically. Customers can verify true dimensions, such as radii, tapers, and flute depths that could previously only be viewed on a comparator."
CNC Expands Precision Production
Mid-State Machine Products began business as a job shop in 1968 in Winslow, ME, and quickly established a reputation as one of the premier CNC precision machining organizations in the US. The company services a broad range of market sectors including defense, gas and oil exploration, and power-generation industries, among others.
The company built its reputation on its ability to produce complex components with demanding geometric tolerances, especially in difficult-to-machine alloys. It is recognized for its ability to deliver "best value" to its customers, and does this with a demonstrated commitment to high quality and on-time delivery, supported by strong customer service.
In October 2006, the company expanded its presence in the precision CNC machining sector, with the addition of a new, technologically advanced facility several miles from its original location. The purpose was to apply in-depth custom machining expertise to a production environment to manufacture four separate components for a large off-road military vehicle.
Today, with the new facility, Mid-State Machine is a fully equipped, precision CNC contract manufacturer with more than 168,000 ft2 (15,608 m2) of modern manufacturing space, equipped with 55 CNC machine tools and numbering more than 220 employees. The company's facilities are ISO-9001:2000, AS-9100A: 2001, and NADCAP (FPI and Welding) certified.
More than $13 million was invested to outfit and equip the new 76,000 ft2 (7061 m2) production facility in Waterville, ME. It currently has 14 new CNC machines, including a range of different-sized horizontal milling and turning centers. Seven of the machining centers in the facility are Makino HMCs, including two a81s, two A100Es, and three A99Es, all of which have been equipped with dual five-axis CNC-controlled rotary tables.
Decision to purchase Makino machines was based primarily on positive recommendations from several sister companies that had been using Makinos in their own machining operations, coupled with Makino's reputation for reliability, uptime, and service.
"We saw how successful these companies were and that they attributed much of their success to the CNC machine tools they were using," says Kevin Nelson, vice president of operations for Mid-State.
"Within a few weeks, we went from an empty building to full production capability," adds Dean Gallagher, Mid-State's shop-floor manager. "We made sure all the equipment we purchased would help simplify our operations. Dual fifthaxis index tables allow us to eliminate setups, increasing the time that we are able to spend producing the parts," Gallagher explains.
"At the new facility, we use hydraulic fixturing and automatic probes to determine the length and diameter of each cutting tool," says Nelson. "This technology allows us to increase the overall productivity of the operations while reducing the potential for human error."
Hydraulic fixturing ensures that consistent pressure is applied to the workpiece in the proper sequence, making sure that the required accuracies are achieved. Automated tool probing verifies that all tool lengths and diameters are accurately measured and transferred into the CNC control with a high degree of accuracy.
"The older machines and processes were much slower and required a significant level of intervention from skilled machinists," continues Gallagher. "The Makino HMCs have resulted in a marked improvement in our overall productivity on these components. They're much smarter, with options like sensors to detect broken tools and extend tool life, ultimately improving the production process."
Thanks to the more advanced machines and table-on-table setup, the company has reduced operations on the part from seven to two, dramatically reducing the machining time for each part.
"The Makino HMCs are also less labor-intensive," says Nelson. "We are able to assign one operator for every two machines, compared to our older equipment, which requires a dedicated operator per machine. This allows us to get more work done in the course of a day with the same number of people," Nelson explains.
"There is no lag time as a result of loading a fixture. If the door is closed, the spindle is spinning. These machines help us deliver higher-quality parts faster than ever before. As a matter of fact, our primary bottleneck over the past year has been related to waiting for raw materials to arrive at our facility."
One of the parts, an air diffuser, is made from 17-4 PH stainless. Using indexable carbide tools, the first operation of roughing and finishing takes approximately 2 hr on a Makino A99E HMC.
Next, the part is sent to a VTC for several additional hours of machining, and then is routed back to another A99E for boring, face work, periphery work, and thread milling.
Finally, the part is deburred and inspected on a CMM to verify the dimensional features. Deburring is a critical step, since the parts require a 32 rms finish in many of the holes and facets, and a 63 rms over the remainder of the surfaces. Once deburred, the parts are sent to assembly.
The new setup has allowed Mid-State to eliminate one CNC machine operation and a manual operation. Prior to the addition, operators were required to manually drill six holes with a jig to complete the features on the air diffuser.
Mid-State was also able to eliminate the peripheral milling operation as the fifth-axis indexers integrated on the Makinos rotate the part to the proper attitude, allowing the spindle to access it for a critical operation. Hand polishing, previously required to clean up the surface, has also been eliminated, letting the part move to assembly directly out of the machine.
"To give you an idea of the complexity we're dealing with here, one of the parts has 800 distinguishable features, which require a wide range of custom tools and sizes," says Nelson. "The laser probe integrated on each of the Makinos allows us to automatically verify the length, diameter, and tool geometry after each tool change with a high degree of accuracy."
The Makino's through-spindle coolant also allows for more efficient cutting by reducing chip recutting, which permits the machine to go from boring to reaming with no human interaction required, and further ensures improved drilling results are achieved on a consistent basis.
With the addition of this equipment, Mid-State Machine is able to routinely produce hundreds of these components on a monthly basis.
Taking all the operations eliminated with the new Makinos, Mid-State Machine reports significant cycle-time reductions.
When Mid-State opened its new state-of-the-art facility, the company saw it as an opportunity to prepare for the future.
"Finding qualified employees has always been difficult for us," says Nelson. "We knew we needed to expand, but we also knew that to support the expansion would require a significant increase in the number of people who were able to do the work in this new, high-tech production environment."
Early on in the process, Mid-State began working with a local school, Kennebec Valley Community College, to develop a class curriculum and coop program to train local students in high-tech production machining.
Many graduates of the program have become full-time employees of Mid-State, and some have even progressed to the point where they have moved to Mid-State's custom job shop to further develop their machining skills.
"Our company is able to benefit from students' knowledge, passion to learn, and natural abilities, while in return the students are able to benefit by establishing a new career path for themselves with great earning potential and a secure future. Overall, this training program has and will continue to serve as an incubator for skilled workers at Mid-State for many years to come," says Nelson. Mid-State has hired 25 graduates from the three classes that have been completed to date, with plans to hire additional people in 2008.
Software Speeds Mold Delivery Up To 75%
Northbend Pattern Works (West Harrison, IN) is a maker of core molds for high-volume casting of metal parts for the automotive, agriculture equipment, pump, valve, compressor, and electric motor industries, among others.
More than 90% of the molds North Bend makes are destined for automotive parts, such as brake calipers.the higher-end automotive and high-production types of patterns. It's complex work with demanding customers.
Northbend's customers, primarily foundries, must deliver tolerances in their castings once expected of machined parts. As a result, they have tightened requirements on mold suppliers. Where 1/16" (1.6 mm) was once acceptable, ±0.005" (0.13 mm) is now the standard tolerance for Northbend, and some customers demand ±0.002" (0.05 mm). This level of precision is expected in addition to an ability to deliver on time and accommodate changes almost overnight.
Investing in technology is not new at Northbend. After 40 years of making precision molds for sandcasters, Northbend Pattern Works founder Dale Ziegler saw the writing on the wall. Recognizing the limitations of traditional patternmaking practices, he installed CNC and EDM systems.
These technology investments have reduced handwork and finishing steps, speeded throughput, improved tolerances, and attracted a high-quality customer base that recognizes and appreciates the company's value-adding capabilities.
The new technology integrated all stages of moldmaking into a systematic process. CNC capabilities allow one operator to run five different machines, and control the whole process involved in converting a pattern to a finished mold.
To help it keep up with changes and quickly manufacture the precise molds required by customers, Northbend invested in CAD and inspection software from Design and Software (Fairfield OH), the local distributor for Delcam Software (Salt Lake City, UT).
"We like the software because it's geared toward the kind of work we do here," explains Neil Rullman, Northbend production coordinator. "With the surface and solid models, it makes it really easy to convert CAD data into tool path and part." Today, Northbend uses Delcam's PowerShape and PowerInspect, which has enabled the company to streamline its moldmanufacturing process and accelerate the turnaround of every mold.
"The Delcam software allows us not only to produce molds directly from CAD data, but also to make changes to the models and produce a new model to return to the customer very quickly," Neil reports. "Rapid, accurate turnaround is essential in our business."
The CAD department uses Power-Shape, while Rullman uses PowerInspect in the production department for quality control. CopyCAD is used to reverse-engineer parts that customers may bring to Northbend.
With PowerShape, Northbend typically imports a solid model from the customer, analyzes models for damaged, duplicated, or missing surfaces, and views difficult areas like thin walls, ribs, and undercut areas. Using process-driven wizards, Northbend designers can extract mold features from imported geometry. Then, when the model comes back from the customer—usually with changes—Northbend can easily replace or modify surfaces and regenerate solid models.
To inspect molds and sample parts, models from the CAD department are downloaded into the Faro arm control, and then key points and features are fully checked on the mold and results compared to CAD data. PowerInspect's onscreen feedback and detailed graphical displays provide immediate feedback for each measured point, and inspection reports can be generated in a format built specifically for Northbend's customers.
As the arm's tip is traced over the part's surface, the system's laptop computer verifies all of the part's 3-D measurements against the original CAD file—the digital blueprint—to see if it was made correctly and, if not, where it needs to be corrected.
The power and speed of the inspection process are important to Northbend's ability to deliver accurate molds quickly.
"With the arm, we can pick specific engineering points on a model and zero in on them, comparing those key spots to design data. We can quickly assure the quality of what we produce. It is very easy to go back and forth between PowerShape and PowerInspect," Rullman explains. This feature is extremely helpful because engineering changes on the parts are almost constant. For even more convenience, the menu bar of the Delcam software can be customized for the type of work done at Northbend.
"We had been pouring a plaster model from the mold and then measuring that, but we purchased the arm recently, and have been moving toward that inspection approach," Rullman says. "It will save us a lot of time and possible errors in measuring a part and comparing that to the data. And fewer production steps will help to improve our mold throughput and quality."
Northbend is continuously seeking ways to take time out of the moldmaking process. Producing a core mold used to begin with a handcarved wood or plastic pattern, though physical models increasingly are being machined with CAD/CAM-generated models. From this original model, Northbend creates a tool path that will be used to cut the mold and an electrode it will use on one of its EDMs to finish the mold. As an exact 3-D representation of the complete mold cavity, the electrode model serves as the final machining process in the pattern and process plan.
From the initial mold provided by Northbend, a foundry usually runs up to 250 test parts, inspects the mold carefully, and sends it to the auto manufacturers. At that point, changes usually happen.
In one example, the final customer did not send the mold back but sent a modified part, and Northbend had to make the mold using that casting. "We scanned it in with the laser, and made the changes in the data. High and low spots compared to the original CAD model were revealed during inspection with PowerInspect.
"The alternative would have been to use calipers and micrometers—an unacceptable waste of time and not nearly as reliable," Rullman says.
Northbend then makes a new model and prototype mold, usually in aluminum, sends it back, and, if it produces the part the customer wants, produces the final mold from tool steel. This is a typical sequence, but at Northbend, it happens fast.
"They can take as long as they want to return parts to us, but once we get it, we have to return the corrected part as fast as possible," Rullman says.
"Because we are not a production shop and get repair and build orders every day, we switch tooling, parts, and programs in the machines almost daily to keep up with the variety of molds we are asked to work with. It's something different every day, and it's all very time-sensitive," he says.
"The main reason we can turn jobs so quickly is that the software is designed to work together; it helps us do what we have to do. That is probably the main advantage. It's not uncommon to get repair jobs Friday night that are to be returned Monday morning," Rullman says.
The shop is working on 20–50 molds at any one time. It produces 100–150 new molds and patterns a year—each to tight tolerances. "From the time we get a model, such as a brake rotor or caliper, to where we can start cutting on it, the elapsed time is probably three to four days at most—compared to weeks previously."
"When we see a technology that can help us to do our job, better, faster or more economically, we will look into it. Delcam has proven itself to us."
This article was first published in the September 2008 edition of Manufacturing Engineering magazine.