Shop Solutions: Cutters, Inserts Improve Productivity, Quality
Quality is never taken for granted at TMF Center Inc. (Williamsport, IN).
"Poor quality shuts us down," states company president Lloyd McGowen. TMF machines components for heavy-duty highway and off-road vehicles, counting among its customers manufacturers such as Caterpillar Inc.
McGowen makes it clear that he doesn't take chances on quality anywhere on the shop floor, particularly in tooling. So, when he was recently looking to increase tool life while reducing cycle time, he had quality on his mind.
McGowen's son Greg runs GL Technologies Inc., a company that makes purchasing recommendations for TMF. To address the tooling problem, Greg McGowen decided to consult with a sales engineer for Walter USA (Waukesha, WI). He had worked with Walter before with good results, and had developed a relationship over eight years of successful Walter tool installations in other machining areas of the company.
In this case, TMF was looking to improve tool life and cycle time when milling a large cast iron fuel block. "We have 800 different dimensions that have to be held in very close tolerances on this component," Greg McGowen explains. "We have to have milling cutters that can handle that."
When Greg McGowen explained his need in the summer of 2004, the Walter engineer recommended the company's Xtra-tec F4042 milling cutters with Tiger tec inserts. The universal shoulder milling cutter provides smooth cutting action with minimal vibration, and allows milling of a true 90º shoulder angle.
Testing of the new cutters and inserts began in July 2004 on 22 Mazak machining centers, and the technology was soon rolled out to 72 Mazak machines. Since the start of testing, tool life has increased from 50 minutes to 120 minutes of cut time. Speeds, which were 700 sfm (213 m/min), are now running above 1000 sfm (305 m/min). Feed rates increased by 50%, and cycle time has fallen from 17 minutes, 8 seconds to 12 minutes, 4 seconds--a 30% reduction. As a result, TMF has been able to increase the number of components delivered without adding any machines on the floor.
Tool breakage is minimal, setups are reduced, and downtime is cut because inserts run longer between changes. And, quality has not only been maintained but improved. "The ability to maintain finish surface requirements more consistently results in a better product," Greg McGowen says.
Lloyd McGowen puts the results into a bottom-line perspective: "Every second we save in production saves $12,000 - $14,000 per year," he says.
Laser System Makes Its Mark
With headquarters in Milwaukee, Rockwell Automation offers more than 500,000 products covering the technologies necessary to implement automation solutions to a wide variety of industries.
The company's Twinsburg, OH, plant manufactures printed circuit boards. Finished boards are marked with the Allen-Bradley name and logo, plus model identifying data. For this, Rockwell was using screen-printed polycarbonate labels and thermal transfer printed polyester labels. The polycarbonate labels were relatively expensive, and minor aesthetic variations caused rejects and occasional problems with shelf life and label adhesion. In addition, the cost of the labels limited the company's ability to cost-effectively produce small quantities of components for private labeling or for niche products.
The ideal marking method would provide a clean, clear, and cosmetic mark without damaging the product, and be indelible and permanent. Rockwell managers were drawn to laser marking for those reasons. The laser could operate in tight locations, and laser marking would eliminate labels. "By marking directly on the plastic housing, we could eliminate a part and get an aesthetically equivalent appearance that will not fade or peel with time exposure to harsh environments," says project manager Gail Ball.
Rockwell identified Geo. T. Schmidt Inc. (Niles, IL) as a potential marking system supplier based on the company's experience and expertise in developing custom marking systems. Working with Rockwell, Schmidt identified application requirements and reviewed potential safety issues.
The proposed solution consisted of Schmidt's Microlase Nd:YAG solid-state diode-pumped laser with a rotating table with two fixture mounting areas. Schmidt had experience with this type of system, and was able to accommodate Rockwell's requests for ergonomic control buttons and a touch-screen. The companies worked together to modify the software needed to integrate the system into Rockwell's manufacturing process.
The laser system eliminated the cost of polycarbonate labels--as much as $5-$10 each--and permanently marked directly on the product. The laser's ability to mark in small and/or recessed areas has allowed Rockwell to design products that can be manufactured more cost-effectively. And, Rockwell can easily reposition the diode-pumped laser anywhere in the plant.
Rockwell expects to use laser marking on more products in the future, not only because the mark is clear and permanent and saves on label costs, but also because more and more of its products are now installed in harsh environments. Products may be mounted on a drill machine, conveyor belt, or bottling machine rather than in a clean control cabinet, and subject to hot water washdowns. This is not an ideal environment for an adhesive label, whereas the permanent laser mark can withstand this punishment.
Machine Switch Eliminates Setups
Moog Industrial Controls (E. Aurora, NY) is a supplier of electro- and hydro-mechanical motion-control technologies. The company's large customer base demands low prices and quick delivery-a situation further complicated by order quantities as low as one piece on parts with complex geometries. A typical "bushing" at Moog, for example, has more than 100 geometric specifications.
The company's traditional production method required multiple machine setups to accomplish blanking, gundrilling, form grinding, multispindle drilling, OD form grinding, internal grooving, honing, deburring, and finish grinding operations. Estimated setup and changeover time for the series of operations was more than 27 hours.
With this system, Moog was producing 100 parts in three, 40-hour weeks--an approximate cycle time of 1.2 hours/part. Tolerances on the subject part were 0.0005" (0.013 mm) on diameters and 0.002" (0.05 mm) on concentricity.
The company wanted to cut costs by reducing setup and lead time. "With the low order quantities inherent in Moog's lean manufacturing system, we needed to find a way to manufacture complete parts in one setup," explains lathe technical coordinator Brian Schuhmann. The redesigned process required considerable custom engineering from both vendor REM Sales Inc. (E. Granby, CT) and Moog to enable machining of each part complete with minimal setups.
Ultimately, engineers decided to use a two-machine approach. The revamped process begins on a Tsugami MU38-SY Swiss-type turning machine for parts less than 1.5" (38-mm) diam and production runs of 20 pieces or more. A Tsugami TMA-8 mill/turn machine was selected for larger-diameter or small-volume parts.
The MU38 is an eight-axis machine that reduced cycle time for producing the sample part complete to 13 minutes, 28 seconds. Tooling included a single-station adapter holding six ID grooving tools--three each for the front and rear of the part. Other engineering changes included high-pressure coolant and gundrilling and cam shape milling capability. The machine's large tool capacity requires changing only 5 - 7 tools for changeover to a new part.
The TMA8 seven-axis Turn/Mill/ Drill machine has a 60-tool automatic toolchanger, which allows production of a variety of parts with minimal tool swapout. A resident library of 1000 tool offsets was produced to help reduce setups and part change over time. All processes, tools and multiaxis offsets are cataloged in a Microsoft Access database.
Records of all tools, axis, and offsets are also stored in a hard copy binder at the machine site, helping 80% of Moog's parts to successfully clear first-piece inspection. "Documentation makes the system work," Schuhmann says.
The system has demonstrated reductions in lead time and increased throughput that are beneficial to both Moog and its customers. The main drivers of cycle time reduction are shorter setup times, absolute control over tooling and documentation, and the ability to run many more part numbers per day per machine.
Reliable Milling Cuts Production Time
Unexpected tool failures can make it very difficult to efficiently machine a product, and tool failure was the challenge faced by AAA Sales & Engineering (Oak Creek, WI). The company needed to increase throughput on a high-volume ductile iron housing while simultaneously eliminating tool failures. The existing process was not reliable and needed to be adjusted in order to produce the parts efficiently.
Founded in 1968, AAA consists of three distinct operating divisions. Railroad Products designs and manufactures classification yard car retarders. The company's Production Machining Division specializes in high-precision, high-volume manufacturing, while the Short Run Division focuses on low-volume manufacturing, including fixture design and prototyping.
On the project mentioned earlier, AAA needed to upgrade tooling to something more reliable than the 2.5" (64-mm) stack mill it was using. After looking at the situation more in depth, engineers contacted their Iscar Metals (Arlington, TX) representative.
With the stack mill, process parameters were spindle speed of 2000 RPM, feed of 60 ipm (1.5 m/min), and axial depth of cut of 0.75" (19 mm). These settings created a lot of harmonics, which in turn led to tool failure and increased production time.
After analyzing the job, the Iscar representative suggested his company's Mill2000, which offers an innovative clamping method that ensures rigidity and reliable machining. A matching dovetail insert and pocket design gives the tools reliable insert seating at high speeds and feeds. The tool is designed so the base of the insert is wider than the rake face, thus creating a dovetail-shaped insert that securely fits into the seat in the toolholder.
According to Iscar, the setup provides improved insert stability even at very high speeds and large depths of cut. The negative angle design of the inserts' helical-shaped cutting edges directs machining forces back up into the cutter body, helping to minimize chipping or breaking that can cause tool failure.
Although speed and feed remained the same on this project, the new tooling was run with a 1.5" (38-mm) axial depth of cut--double the old process. As a result, in-process time was reduced from 28 to 14 minutes. The rigidity of the new tool also substantially improved tool life, from a previous best of 16 parts up to a reliable 22 parts per insert.
Laser-Guided AGVs Add Flexibility
"Our original wire-guided AGV system was built in Japan by the same company that designed our ASRS and crane system," recalls Barry Hansis, staff engineer-stamping at Mitsubishi Motors North America (MMNA; Normal, IL). "The AGVs were controlled by a mainframe computer and weren't very flexible. Plus, getting technical support from Japan was very difficult."
After several years of trying to maintain and improve the old system, MMNA installed a new laser-guided system that corrected the problems and eliminated the continual troubleshooting and maintenance needed to keep the old system running. The new system, from AGV Products, Charlotte, NC, is controlled by a Windows-based PC that allows changes in vehicle paths to be accomplished in a few minutes.
MMNA operates two, eight-hour shifts a day, five days a week, using more than 850 robots to produce nearly 180,000 vehicles per year. The plant produces five different vehicles, including Mitsubishi Eclipse, Spyder (a convertible version of the Eclipse), Galant, Endeavor (an SUV), and the Chrysler Sebring and Dodge Stratus.
"We have a stamping facility attached directly to the body assembly area," Hansis explains. "Stampings for the vehicles are produced on-site. Coiled steel is fed into a blanking press producing stacks of blanks used to manufacture the parts. These stacks of blanks are stored in an ASRS until they're ready to be used. When the blanks are needed for production at the transfer press, the AGVs move the stack from the ASRS system to press.
According to Hansis, the AGVs had been used in the stamping area since the plant first opened in 1988. Problems with maintenance and technical support plagued the first system, and vehicle batteries had to be charged several times a shift.
"Our primary goals when searching for a new AGV system were maintenance-free operation and user-friendly system control," Hansis says. "The new system's host computer controls the AGVs, runs the cranes in the ASRS, controls inventory, schedules and controls deliveries, and routes the AGVs. The computer is constantly looking for the most efficient way to route the AGVs. We can also connect with other computer systems throughout the plant."
The new vehicles use a laser-guidance technology that allows vehicle path changes to be accomplished in a matter of minutes, as well as gel-filled batteries that can be quickly charged every time a vehicle returns to its home position. The result is no battery changes and no lost production time.
The vehicles are from AGV Products' Odyssey line, and are equipped with iCon (Intelligent Computer Optimized Navigation) navigational software. They have a laser unit mounted on top of the mast and calculate their coordinates from reflectors permanently mounted all over the shop. All vehicles are equipped with an advanced safety system that includes front, side, and rear sensors as well as a laser bumper detection system.
"In our shop, the paths the AGVs take are fairly static," Hansis says. "However, with the laser guided system it is very easy to change the path-it's just a click-and-drag operation on a PC. Permanent changes to the guide path must be made by our management staff, but special deliveries, inventory changes, error recovery, and daily operations can be accomplished by associates on the floor."
This article was first published in the June 2005 edition of Manufacturing Engineering magazine.