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Modern CNC grinders are designed to minimize vibrations with advanced software that evaluates factors such as dynamic and static stiffness. Spindles, slides, ways, and other components are built to stringent specifications to increase rigidity and improve vibration. Despite machine design advancements, grinding is becoming more difficult for industries such as aerospace. Tolerances have tightened considerably and material removal rates (MMR) for high nickel alloys, ceramic matrix composites (CMC), and metal matrix composites (MMC) are pushing machine capabilities to the limits, increasing the probability of vibration.
Common forms of vibration on grinding machines tend to fall into two categories force vibration and self-excited vibration. Force vibration includes wheel imbalances, damaged bearings, bad motors, or grinding wheel imbalances. Force vibration can be present even when the grinding wheel is not in contact with the workpiece. Self-excited vibration occurs only during grinding, due to grinding parameters, the process, and certain machine characteristics such as natural frequencies of the machine.
During grinding, undulations/waves can start to form on either the workpiece or the grinding wheel as fluctuating forces excite a natural frequency on the machine. The undulations continue to grow with each rotation of the wheel. This continues until the workpiece quality diminishes to the point that grinding needs to be stopped. Typically, the wheel is then dressed and the cycle repeats. Waves forming primarily on the wheel are said to be due to wheel-regenerative vibration, and waves forming primarily on the work are said to be due to work-regenerative vibration.
When the vibration amplitude becomes excessive, it can become detrimental to workpiece quality. The amount of vibration that would be considered excessive depends on the application. A precision cylindrical grinding operation may require displacement values below 0.03 mils (0.00003") whereas a cutoff operation at a steel mill could be greater than 1.00 mils (0.00100") peak-to-peak. Typically, acceptable vibration level is driven by workpiece tolerances, such as dimensional tolerance, surface finish, waviness, roundness, and undulations per revolution. The tighter the tolerances, the more the vibration needs to be minimized. Excessive vibration can also increase wheel wear, damage (burn) material, and cause early spindle bearing failure.
The grinding spindle bearings typically need to operate at high speeds while withstanding high loads and grinding forces. Any wear or damage to the bearing will transfer to the workpiece as chatter or poor finish quality. Depending on the severity of the operation, the spindle bearings may last for years with no issues, but other, more intense operations may require bearings to be repaired or replaced more frequently.
There are many potential sources for machine vibration and great care should be taken when determining the true source. This is especially important when planning machine maintenance and repairs. In some instances, thousands of dollars have been wasted repairing or replacing spindles, only to discover that the spindle was not the problem. Diagnosing vibration problems can be complicated and require advanced equipment and an experienced vibration analyst. Useful, basic vibration analyses can be completed by relatively inexperienced personnel using iPads.
Vibration monitoring of grinding machines can help reduce delays in production, product rejections, late deliveries, and increased manufacturing costs. It can also help to quickly identify the source of vibration. If you are responsible for keeping grinding machines running and making quality parts, consider vibration monitoring of your machines. The investment could save time, money, and headaches.
The material was difficult to grind and the components were expensive. Prior to monitoring vibration, the spindles were run until the operator determined a problem, either by realizing that the spindle was overheating, becoming noisy, or seizing up. This often resulted in costly scrapping of workpieces. A preventive maintenance procedure periodically checked the spindles vibration levels. If the vibration reached the predetermined limit, the machine would be shut-down and the spindle replaced. A graph of the Y-axis vibration severity and the X-axis shows the speed range of the machines. Measurements were taken and recorded at each of the speeds. This procedure eliminated part rejection due to spindle failure.
Less than 72 hours before Labor Day in 2014, a jet bridge at the Honolulu International Airport (HNL) collided with a Japan Airlines (JAL) Boeing 787 Dreamliner, damaging an engine cowling and disabling the plane. Far from their home station, JALs maintenance, repair, and overhaul (MRO) team faced a tight deadline to remove the aircraft. Losing time and money, the team contacted UPS to transport a 3,500 lb replacement cowling that waited 2,600 miles away.
JAL was one of the first airlines to fly the lightweight, fuel-efficient 787 Dreamliner, so spare parts especially parts that weigh nearly two tons werent readily available. Throw in the holiday weekend, and a solution seemed impossible.
In most cases, we would have a spare aircraft available to substitute for the grounded one. But at a foreign airport, we were forced to cancel the flight, says Takashi Ogata, logistic management staff manager for JAL Engineering.
This kind of aircraft downtime means a significant revenue loss from flight schedule disruptions, cancelled flights, and additional expenses such as layover fees, hotel accommodation, and food and beverage expenses for passengers, Ogata says. But what worried us most was losing the confidence of our valued customers.
On Saturday, Aug. 30, 2014, one day after the plane was grounded, JALs MRO team located a replacement cowling at a UTC Aerospace Systems facility in Chula Vista, California. Now, the team had to figure out how to get the cowling to Honolulu. Ogata called Yuichiro Asari, JALs UPS account executive in Tokyo. The clock was ticking as HNL wanted the plane removed within seven days.
The size of the cowling and requirements to move it as soon as possible made this challenging, says Mark Lombardo, general manager for UPS Supply Chain Solutions. The first step was to secure a lift to Hawaii. Then, the UPS crew could arrange ground transportation.
Early in the morning of Friday, Sept. 5, 2014, one day short of the deadline, a flatbed truck transported the engine from Chula Vista to the San Diego International Airport (SAN). The 16-mile drive required special permits and an escort vehicle for the oversized load.
For UPS to arrange this transportation, it needed urgent information about the cowling from JALs MRO team. Lombardo says understanding the dimensions were just as vital for the ground move as they were for the air. Ground transportation required a special trailer and several permits, there were curfew hours during which the load would not be allowed on the road, and UPS had to follow a prescribed route. UPS employees worked under these strict requirements for an on-time delivery, communicating constant updates to JAL.
The next morning, JALs MRO team stood by when the 747 charter landed in Hawaii to install the cowling. The newly repaired 787 Dreamliner then departed Honolulu for Narita International Airport in Japan.
The coating by the Rice lab of chemist James Tour may be an effective, real-time de-icer for aircraft, wind turbines, transmission lines, and other surfaces exposed to winter weather, according to a new paper in the American Chemical Society journal ACS Applied Materials and Interfaces.
The lab melted centimeter- thick ice from a static helicopter rotor blade in a -4F environment. When a small voltage was applied across the composite, the coating delivered heat called Joule heating to the surface, melting the ice.
The nanoribbons produced commercially by unzipping nanotubes, a process also invented at Rice are highly conductive. Rather than trying to produce large sheets of expensive graphene, the lab determined that nanoribbons in composites would interconnect and conduct electricity across the material with much lower loadings than traditionally needed.
The researchers fabricated a conductive composite of graphene nanoribbon (GNR) stacks and epoxy, which serve as a conductive additive. On average, the GNR stacks are 30nm thick, 250nm wide, and 30m long.
In tests, nanoribbons were no more than 5% of the composite. Researchers, led by Rice graduate student Adul-Rahman Raji, spread a thin coat of the composite on a rotor blade segment supplied by a helicopter manufacturer. They then replaced the thermally conductive nickel abrasion sleeve used as a leading edge on rotor blades, and were able to heat the composite to more than 200F.
For wings or blades in motion, the thin layer of water that forms first between the heated composite and the surface should be enough to loosen ice and allow it to fall off without having to melt completely, Tour says.
Co-authors of the paper are Rice undergraduates Tanvi Varadhachary and Kewang Nan; graduate student Tuo Wang; post-doctoral researchers Jian Lin and Yongsung Ji; alumni Yu Zhu of the University of Akron; Bostjan Genorio of the University of Ljubljana, Slovenia; and research scientist Carter Kittrell.
The Edge X-5 5-axis waterjet cuts precise, taper-free parts from a range of materials. The waterjet system is capable of cutting 3D parts such as impellers and bevels up to 50. Sturdy design separates the motion system from the catcher tank to eliminate vibration and ensure part quality. The ballscrew-driven system features direct-couple AC brushless digital servo motors, providing the repeatability at 0.001". Critical bearing components are protected with heavy metal covers with brush seals and positive air pressure.
The 3-fluted Tritan-Drill allows more bores, longer tool life, lower machining costs, and higher feed-rate machining. The drill provides rounder bores and reduced burr formation, while its geometry produces optimum chip removal and low cutting pressure. It handles difficult drilling situations such as cross bores, inclined bore entrance, and long-chipping materials. The drill machines steels, cast materials, and non-ferrous metals and is available in diameters of 5mm to 20mm in designs up to 8xD.
The RB-10 robotic grit blast surface preparation system has a 60" x 60" finishing chamber with a reinforced 60" x 48" vestibule at the rear to house an ABB Robotics IRB-2600 robot for a single pressure-blast nozzle. A 24" diameter turntable inside the blast enclosure is servomotor-driven and controlled as a seventh axis of robotic motion, enabling precise orientation of the workpiece. To handle heavy components, the system comes with a crane slot and a roof-mounted jib hoist with a 500 lb capacity.
Used grit is delivered to the base of a bucket elevator with a cascade air wash separator at its top. Once dust and fines are extracted from the blasting grit, it passes through a vibratory screen classifier, and abrasive grain of the specified size is returned to a 10ft3 capacity pressure pot. An automatic media adder replenishes the grit supply from a storage hopper when electronic sensors detect a low media level.
The robot-based additive manufacturing (RAM) platform for fabricating 3D printed composite parts consists of a standard robot, composite deposition end-effector hardware, and a software suite. Designed for ABBs IRB 120 6-axis robot, the scalable software can support larger ABB robot models and sizes. The additive end-effector hardware consists of a deposition head with advanced thermal management technology for processing high-performance carbon-fiber reinforced thermoplastic filaments.
The solution maximizes size, scalability, and production efficiency, enabling technologies such as automation and secondary process integration within manufacturing work cells. Depending upon the size of the robot, the part build envelope is scalable from 1,000mm3 to 8m3.
TH1000 and TH1500 turning insert grades have positive and negative geometries, chip breakers, and nose radius sizes, allowing increased machining capabilities for manufacturers that process hardened steels, superalloys, and cast irons.
Edge toughness and high chip resistance of the TH1000 TiSiNTiAlN nanolaminate PVD-coated grade is designed for ISO H5-H10 applications. The insert maintains long tool life when machining hardened steels from 50HRC to 62HRC, hard surfaced components, and superalloys. TH1000 excels in finishing operations and interrupted cuts in hardened steels. When machining Inconel 718, Waspaloy, and Nimonic C263, the grade brings fast cutting speeds to continuous finishing and semi-finishing operations.
When processing hardened steels, from 40HRC to 55HRC, the Duratomic TH1500 grade is for ISO H10-H15 applications requiring high cutting data and continuous-cut operations. TH1500 provides finish turning of grey and ductile cast irons in applications with low-to-moderate cutting speeds.
Its advanced grade profile includes an abased Al2O3 CVD coating, Ti (C,N) middle layer, and a super fine-grain substrate, making it an alternative to CBN and ceramic cutting tools in machining hardened steel workpieces in unstable conditions.
Costimator Version 14 includes 3DFX automated feature recognition (AFR) , enhanced cost models, cost/profit reports, and SQL server 2014 compatibility. The 3DFX AFR add-on recognizes CAD features and their parameters from solid models giving estimators control over features they extract and import, increasing cost estimating and quoting throughput up to 90%.
The 300GMSP turnkey gear inspection system is designed for aerospace, automotive, and smaller power transmission industry applications. An active leveling system attenuates a broad spectrum of normal production environment vibrations, producing measurement values in parallel with those achieved in controlled calibration laboratories. Shop floor thermal fluctuations are proactively compensated, allowing for reliable inspection results. The system identifies and applies a compensation for factory floor influences in real time.
The Series 320 electronic weld head system is for precise position and force control applications including squib wire, fine wire, and electrode welding. Suitable for microelectronics manufacturing, as well as for industrial requirements and environments, it features inline and offset opposed electrode configurations for flexibility, and accurate force and position parameters. Users can set displacement limits using a weld-to-displacement feature to stop the weld precisely during collapse. The I/O offers four programmable relay outputs for integration with programmable logic controllers.
The Vericut CNC 7.4 simulation software features faster processing speeds, supporting longer tool life and increased part quality. The systems desktop has a docking method enabling Vericuts desktop to be configured with server customization options. An updated status window provides better viewing, customization, and size with information divided into groups, each containing a specific list. The softwares tool managers desktop and user interface is redesigned to enable easier user interaction. Vericut 7.4 ships with a library of common tools.
Cimperial 861 with InSol Technology a hybrid lubricity, semi-synthetic metalworking fluid is approved under Bombardier BAMS 569-001 Revision B and is recommended for heavy-duty machining of non-ferrous and ferrous metals, including 6000 and 7000 series aluminum, stainless steels, and titanium. It can also be used for grinding and is formulated to deliver extended sump life. The product is designed to increase tool life and provide lubricity while remaining low-foaming in high-pressure applications. It has low chemical odor and is mild to the skin.
Multi-blade reamers produce precision bores with up to 150% faster feed rates and reduced cycle times when compared with single-point tools. Increased production coupled with longer service life lowers the total cost of ownership. Standard tooling is available with short or long shaft lengths, with or without internal coolant supply, and in diameters from 5.600mm to 60.599mm (special diameters to 100.599mm).
NCL V10.1 determines pocket boundaries and whether it is open or closed. Tool path calculations adjust to overlap the open boundaries of the pocket and stay within its walls and accommodate fillets between pocket floor and walls. Rotary axes setup in PostWorks, NCCS universal 10-axis post-processor, can be defined to rotate about any vector, allowing definition of more complex rotary table/head type machines.
Rota NCS is a lathe chuck with active pull-down action of the jaws, suitable for external and internal clamping applications and available as a 3- and 6-jaw chuck. In the 6-jaw version, the pendulum mechanism is integrated, which can be adjusted in pairs for sensitive, deformation-free clamping of thin-walled parts.
The TuffCut XT series 278, 5-flute high-performance end mills include more than 400 added items for additional lengths of cut, corner radii, and Weldon flat options. The end mills minimize process downtime and maximize productivity and cost efficiency, and are coated with Altima Blaze to enhance edge protection for applications in steels, stainless steels, special alloys, and cast irons.
Four models join the Puma GT series of turning centers offers: Puma GT2600, GT2600M, GT2600L, and GT2600LM. The models include a 30 single-piece slant-bed design, box guideways, fast non-lifting servo driven turret, and EZ Guide i conversational programming system.
Standard chuck size is 10" (optional 12") with a maximum swing over bed of 24.8" and swing over saddle of 18.1". Maximum turning length is 25.9" on the Puma GT2600; 24" for Puma GT2600M; while the long bed versions offer 42.4" on the Puma GT2600L and 40.6" on the Puma GT2600LM. Maximum bar working diameter is 3.2" on all four models.
Aerospace Manufacturing and Design welcomes all aircraft enthusiasts to join the fun and NAME THAT PLANE! Each issue, a new aircraft will be featured. Given a photo and a clue box, readers are encouraged to guess what plane is being described and submit their answers to www.OnlineAMD.com/NameThatPlane.
I took lessons when I was 13 at McChesny Airport in Rockford, Illinois, where the Experimental Aircraft Association (EAA) formerly held its conventions. I always enjoyed seeing all the aircraft come in for that event. I am currently a member of EAA Warbirds Squadron 3 in Indianapolis, Indiana.
Ultra-precision grinding is primarily used to generate high quality and functional parts usually made from hard and difficult to machine materials. The objective of ultra-precision grinding is to generate parts with high surface finish, high form accuracy and surface integrity for the electronic and optical industries as well as for astronomical applications. This keynote paper introduces general aspects of ultra-precision grinding techniques and point out the essential features of ultra-precision grinding. In particular, the keynote paper reviews the state-of-the-art regarding applied grinding tools, ultra-precision machine tools and grinding processes. Finally, selected examples of advanced ultra-precision grinding processes are presented.
This paper deals with the fabrication of micro cylindrical tools and micro flat drills of ultra-fine grain cemented carbides by grinding with ultrasonic vibration. The concept of this grinding is to reduce the grinding forces such that they will not cause any breakage to the micro tools. The grinding operations are performed using the end face of an offset grinding wheel. In grinding with ultrasonic vibration, better results in aspect ratio and tools of smaller diameter than conventional grinding are obtained. Due to the lower tensile strength of carbides, grinding under compressive force has made it possible to grind to a diameter of 11 m with a length of 160 m.