MANUFACTURING

LORD Corporation (formerly BalaDyne Corporation)

Superior, Real-Time Balancing System for High-Speed Machining

View PDF Document Text Only Version Patent Tree

The U.S. manufacturing industry uses spindles to cut, mill, and drill metal or other objects into products for commercial use. Spindle-balancing equipment is used to detect vibration and correct balance as the spindle turns and cuts. Balancing systems enable the production of higher precision parts with better surface finish for products such as vehicle engine blocks, transmissions, axles, and suspension components.

In early 1997, BalaDyne Corporation, a small company that manufactured spindle-balancing equipment, proposed to develop a new active (in motion), real-time, high-speed balancing system. The proposed system would need improved bearing technology, innovative sensor and vibration control methods, and new balancer mechanisms. Furthermore, the system’s active balancing capabilities were targeted for an increase from 5,000 revolutions per minute (rpm) to between 40,000 and 50,000 rpm and define a pathway to 100,000 rpm. Due to the high level of technical risk involved in this project, BalaDyne was unable to attract private funding. The company turned to the Advanced Technology Program (ATP), and in 1997, ATP awarded cost-shared funding as part of its “Motor Vehicle Manufacturing” focused program. If successful, the project could create a competitive edge for U.S. automakers by improving part quality and manufacturing throughput.

At the conclusion of this project in 2000, BalaDyne had validated in a laboratory setting significant technical success, including reduced spindle vibration, improved balancer response time, and increased maximum balancer rotational speed. Attracted by these accomplishments, LORD Corporation acquired the entirety of BalaDyne’s real-time, high-speed balancing operations in 2001. LORD continued to develop the balancing systems and, by 2003, was marketing systems enhanced by the ATP-funded technology. These balancing systems have been sold to parts manufacturers primarily for vehicle industries, thereby enabling more lightweight and durable products for the American consumer, and to cement plants, making them more productive. This project produced two patents along with peer-reviewed journal articles, dissertations, trade association publications, and news articles.

COMPOSITE PERFORMANCE SCORE
               (based on a four star rating)
* *

Research and data for Status Report 97-02-0053 were collected during January – February 2006.

BalaDyne Aims to Develop an Active, High-Speed Balancing System A spindle is a motor-driven shaft that powers tools used for cutting, milling, or drilling. As the spindle motor rotates, the tool used to cut metal vibrates, causing an imbalance of the assembly and producing a less precise cut. Cutting precision can be further compromised as spindle rotation speeds increase.

During the 1980s and 1990s, active balancing systems were developed and used to perform balancing corrections to spindles. By the late 1990s, however, real-time, high-speed balancers for machine tool spindles were limited to speeds of less than 12,000 revolutions per minute (rpm). The available sensors attached to the spindles could not analyze the level of vibration and the balancers could not correct imbalances during higher speed spindle acceleration. It was critical to identify

and control vibration in order to minimize imbalance and maximize the quality of parts produced. Poor cutting produces parts out of specification. As a result, production lines would be shut down for laborious off-line balancing adjustments. In early 1997, BalaDyne Corporation was a small, 25-employee company that manufactured and sold machine-spindle-balancing equipment. At that time, BalaDyne’s balancers used liquid to correct imbalance. While adequate for lower speed spindles, this method did not have the precision or response time for higher speed spindles. The solution was to develop an all-mechanical system. The objective of BalaDyne’s ATP-funded project was to develop an electromechanical balancer to provide a balancing system that could detect and correct rapid vibration along multiple locations on a high-speed spindle, resulting in more efficient machining and superior products and tool performance. Among the high-risk technical challenges would be improvements to bearings, a method for attaching balancers to the spindle, a more sophisticated sensor and signal-processing system, and a new multiple-location vibration control system capable of operating at speeds greater than 40,000 rpm. If successful, this high-speed, real-time balancer would improve the production, precision, and reliability of high-speed machine tools in vehicle component and other manufacturing, as well as in process plants for equipment such as large fans. The project could save hundreds of millions of dollars through improved production capability and product quality, while reducing maintenance and manufacturing costs. After first evaluating the overall technical challenges in creating the system, BalaDyne divided the work into two parts. The first part of the project focused on developing a new balancing control system mechanism and diagnostic technology. BalaDyne worked with a subcontractor, the University of Michigan, on these aspects of the project. Professors Jun Ni and Jan Shi and their graduate students researched and analyzed signal processing, estimation, and control of high-speed machine tool structural dynamics. The specific tasks for estimating, analyzing, and controlling high-speed spindles involved the following:

· Developing new methods for vibration sensing and signal processing · Creating new methods to detect the amount of imbalance during high-speed acceleration · Developing a single and multiple-input, multiple-output adaptive vibration control system (Single and multiple-input, multiple-output refers to the number of transmission information signals that can be used to detect and control vibration.) The second part of the project focused on new mechanical designs and the capabilities of specific components for the high-speed balancer. This part of the project had four major elements: · Developing improved bearing technology · Developing a new method of attaching balancers · Developing high-speed sensing, control, and balancer methods to allow the rapid minimization of vibration · Designing, analyzing, and fabricating the high-speed balancer In order to define the overall measurable success of this project, a new high-speed, real-time balancing system needed to meet the following criteria: · The system could achieve and maintain a G-.04 (highest level, as defined by an ISO standard) balance quality grade. While some tools and toolholders are balanced to G-1.0 (second highest level) specifications, precision balance often cannot be sustained after the insertion of the toolholder into the spindle.^1 · The company hoped to achieve complete balancing in one second or less during spindle acceleration (reduced from 5 seconds). · The system would operate on machine tool spindles rotating at speeds of greater than 40,000 rpm (increased from 5,000 rpm).

¹The industry-standard spindle/tool/toolholder assembly cannot guarantee better than a G-6.3 specification (the fourth highest level).
The top five balance-quality grades recognized by the International Organization of Standards are G-.04, G-1.0, G-2.5, G-6.3, and G-16.0.

· The system would control vibration simultaneously in multiple locations with multiple sensors (as opposed to controls along a single plane using pairs of sensors). If successful, BalaDyne’s technology could be applied not only to motor vehicle manufacturing (engine blocks, transmissions, axles, and suspensions), but also to aerospace manufacturing, high-speed industrial turbomachinery, and aircraft turbine engines. The high-speed industrial turbomachinery and aircraft turbine engine applications could be used in other segments of the U.S. economy including petroleum, chemical, agricultural, power generation, and defense industries. Research Project Moves Forward In developing the high-speed balancing system, BalaDyne pursued research efforts in seven major areas. The company collaborated with Professor Ni and the University of Michigan Manufacturing Research Center on the first three vibration and control tasks detailed below. 1. Sense vibration and process signals: BalaDyne initially determined that combining a process for estimating instantaneous rotating speed with a system that could instruct the machine to terminate balancing changes when target specifications are met was achievable and critical to project objectives. 2. Estimate the level of vibration during high-speed acceleration: BalaDyne tested order-tracking vibration signal processing, a method that measures vibration, and determined that it was inadequate for rapidly varying spindle speeds, especially while accelerating toward the most critical cutting speeds. They developed a number of algorithms to estimate imbalances by using a transient vibration signal (a signal that changes with respect to time). 3. Develop control strategies: BalaDyne achieved successful results when it tested two different control methods for balancing during spindle acceleration on an actual machine tool. Both the gain-scheduling and positive-real control strategies (systems that analyze and control the behavior of dynamic movement) were able to minimize vibration during acceleration and

make the counter-weight balancer move to the desired position to correct for spindle imbalance. The positive-real control method proved so successful that the application could be extended to other applications, such as fan and turbomachinery operations. 4. Design low-friction bearings: BalaDyne identified various bearing designs that could potentially meet high-speed machine tool demands for new, low-friction bearings. These designs, which were X-type, C-type, and roller bearing, could achieve 24,000 rpm or greater. A new ball-bearing technology proved to be the better choice for high-speed balancing, although it was a more expensive option. 5. Develop a method to attach balancers securely: BalaDyne successfully developed and tested a balancing device capable of withstanding a speed of 24,000 rpm when spindle-mounted and a 30,000-rpm system when toolholder-mounted (a toolholder-mounted operation is an assembly that includes a cutting tool, a holder for that tool, and a spindle for the purpose of machining an object). BalaDyne then developed and tested a 40,000-rpm balancer design. Their design modifications and tests resulted in a balancer capable of operating at 42,000 rpm in the laboratory environment. 6. Develop high-speed sensing, control, and actuation methods to allow rapid elimination of vibration: BalaDyne created a prototype balancing device that featured seven sensor targets on each balancer rotor. Six of the targets provided intermediate position feedback, and the seventh acted as an absolute phase reference (values that never change). In addition, BalaDyne developed a sensing method and position feedback controller to keep the balance rotor in position. 7. Produce a prototype high-speed balancing system: BalaDyne acquired a 40,000-rpm spindle, frequency converter, and cooling unit. This prototype balancing system included hardware and a digital signal processor (DSP) device to measure real-time outputs. The company procured a more robust test spindle to measure balancers at 40,000 rpm without having to rebuild the spindle bearings. They tested

the DSP controller and ran algorithms developed for sensing vibration and processing signals. At the conclusion of the ATP-funded project in September 2000, BalaDyne had overcome many of their technical challenges and had achieved the following: · Developed models that could test and analyze vibration as well as estimate and control vibration · Developed signal-processing methods to more accurately estimate frequency vibration during changes in spindle speed · Applied these methods to nonstationary signals to control vibration during spindle acceleration · Created specialized bearing technology that featured a new “cage” for holding the bearing and reducing friction · Controlled the amount of imbalance at multiple locations using the new balancer systems · Developed attached balancing devices capable of withstanding 42,000 rpm, which was a significant increase over the then state-of-the-art level of 5,000 rpm, but limited top speed to 25,000 rpm due to bearing capability limitations · Developed a balancer configuration that would allow faster balancing at higher speeds BalaDyne achieved measurable technological advancements in balancing accuracy, correction response, vibration control, and machine tool balancing speed. In the area of assembly balance accuracy, BalaDyne’s technology improved from a G-6.3 to a G-1.0 level (a two-grade improvement) for the spindle/tool/toolholder assembly. In the area of balancing speed correction response, the technology advanced from achieving balancing in greater than five seconds after reaching a steady spindle operating speed to achieving balancing in less than one second prior to reaching a steady spindle operating speed. And in the area of balance and vibration control locations, the technology advanced from single-plane balancing with a pair of vibration sensors, to dual-plane balancing

with two pairs of vibration sensors. Prior to ATP funding, real-time balancing products were limited to spindle speeds of no more than 5,000 rpm, while this new proposed technology targeted active machine tool balancing in the range of 40,000 to 50,000 rpm. This process would allow end-users to minimize product imbalance, reduce the number of products cut outside of specifications, and reduce the amount of time for assembly line shutdown and manual machining adjustments. Prior to ATP funding, real-time balancing products were limited to spindle speeds of no more than 5,000 rpm, while this new proposed technology targeted active machine tool balancing in the range of 40,000 to 50,000 rpm. While this technology was initially envisioned only for high-speed machining spindles, these advancements gave rise to the possibility of mounting small balancing devices onto interchangeable toolholders (toolholders are devices that attach the cutting tool to the spindle). Further, the balancing system technology can be used for aircraft propellers (including those on helicopters), as well as power generation and petro-chemical equipment such as turbines, compressors, pumps, motors, and generators. Project Success Leads to Acquisition by LORD Corporation A downturn in the machine tool industry in late 2000, along with only a gradual acceptance of this new balancing technology by the manufacturing market, slowed commercialization. This gradual acceptance of the technology was due to the high purchase and installation costs of the balancing system as well as concerns on not achieving rapid short-term return-on-investment. The technological complexities of this new product, application-specific engineering, and development and manufacturing costs for BalaDyne became obstacles as well. However, BalaDyne’s proven technical successes led to LORD Corporation purchasing BalaDyne in 2001. This acquisition subsequently accelerated development with further investment and acceptance of their high-speed, real-time balancing tools.

LORD continued technology development and invested considerable resources in the new balancer system. In 2003, the company introduced three innovative high-speed, real-time balancing systems on the commercial market. These systems were: · LORD Balancing System for turning centers, high-speed grinders, and machine centers · LORD Turbomachinery Balancing System for turbines, compressors, pumps, generators, and motors · LORD Fan Balancing System for large industrial and small equipment fans These systems benefited from accomplishments made during the ATP-funded BalaDyne project. Each balancing system is comprised of sensors, a controller, one or more activation coils and balancers within a balancing system that detects, monitors, and reduces vibration while the machine operates at various speeds. When vibration occurs, a sensor transmits information to the active control system, the control system then sends a signal(s) to the coils, and the coils then move the counterweights that are inside the balancer. Vibration correction occurs within a second as a result of the repositioning of these counterweight balancers, all while the spindle or machine continues to run. Figure 1 shows the LORD Balancing System while Figure 2 shows a technician installing a balancer to the spindle. Figure 1. The LORD Balancing System is ideal for vibration correction for turbines, compressors, pumps, generators, and motors. The key components of the balancing system are the sensors, the controller, the coil(s), and the balancer(s). This innovative balancing architecture and signal processing system allows for active balancing within one second of vibration detection.

Figure 2. Application of balancer to spindle. As of 2006, the three LORD balancing systems improve the quality of products requiring high-speed and precision turning. These products have applications that range from automobile transmissions to aircraft engines and propellers to machined human joint implants that are lighter in weight, have improved surface finish, and increased life. Overall, users of LORD balancing systems experience a 40-percent reduction in cycle times and a 30-percent increase in control range, leading to more efficient and less costly manufacturing operations for American businesses. The success of the new active balancing system resulted in two patents and the publication of dissertations, technical papers, and trade journal articles. The three LORD balancing systems have applications that range from automobile transmissions to aircraft engines and propellers to machined human joint implants that are lighter in weight, have improved surface finish, and increased life. Despite technical successes and the development of three high-speed balancing systems, each with multiple applications, widespread use of this high speed machining technology failed to materialize. The declining state of the U.S. manufacturing industry as well as the high installation and equipment costs related to these real-time, high-speed machining balancing systems severely hindered its utilization, leading to slow implementation of this technology.

Conclusion From October 1997 to September 2000, BalaDyne Corporation, in partnership with the University of Michigan, developed technologies that led to the creation of a new real-time, high-speed balancing system. Among the key features of this system were new vibration control methods and signal processing algorithms. The ATP-funded project resulted in specialized bearing technology and balancer configurations that allowed for faster balancing at higher speeds. BalaDyne developed a high-speed, real-time balancing assembly that could correct an imbalance problem in less than one second for a spindle speed of 40,000 rpm, and, in the area of balance and vibration control location, advanced from using a single plane with a pair of sensors, to using two planes with two pairs of sensors. In 2000, the market initially developed very slowly due to the declining U.S. machining industry, the technical complexity of this new product, and the significant user installation and equipment costs. BalaDyne found itself in the challenging position of addressing future cost and marketing obstacles prior to moving these tools into the commercial arena.

The ATP-funded technical successes achieved in the laboratory attracted the attention of LORD Corporation, which purchased BalaDyne in 2001. By 2003, after continued development and marketing, the LORD Corporation had commercialized three innovative high-speed, real-time balancing systems. These systems are being used by customers in the automotive and processing plant industries and have resulted in the production of improved products and greater efficiency in manufacturing. Despite LORD's development of these three balancing systems, the technology has been unable to significantly penetrate the U.S. high speed machining balancing hardware market due to high installation and equipment costs. Additionally, the declining state of the U.S. manufacturing industry has contributed to the very gradual adaptation of the LORD and similar high speed machining balancing systems.

PROJECT HIGHLIGHTS
LORD Corporation (formerly BalaDyne Corporation)

Project Title: Superior, Real-Time Balancing System for High-Speed Machining (Real-Time, Active Balancing for High-Speed Machining) Project: To develop real-time vibration control technology to enable mass balancing of high-speed machining tools that could help companies reduce downtime, extend bearing and machinery life, and increase the quality and precision of parts for automobiles and other products. Duration: 10/1/1997 - 9/30/2000 ATP Number: 97-02-0053 Funding (in thousands): ATP Final Cost              $1,984    67.6% Participant Final Cost      952    32.4% Total                            $2,936 Accomplishments: With ATP funding, BalaDyne accomplished the following: · Increased spindle cutting precision by reducing high-speed vibration · Completed balancing in one second or less during spindle acceleration, an improvement factor of five · Demonstrated active balancing of 40,000 to 50,000 revolutions per minute (rpm) in a laboratory environment, up from industry’s production speeds of around 5,000 rpm · Achieved vibration monitoring and control along multiple locations, improved from a single location BalaDyne received the following patents for technologies related to the ATP-funded project: · “Method and apparatus for balancing” (No. 6,618,646: filed March 31, 1999, granted September 9, 2003) · "Balancer” (No. 6,364,581: filed February 8, 2001, granted April 2, 2002)

Commercialization Status: While BalaDyne did not bring a product to market immediately after the completion of the ATP-funded project, the company’s technical successes during the project led to LORD Corporation purchasing BalaDyne in 2001. By 2003, the LORD Corporation was marketing three innovative and commercially successful real-time, balancing systems based on the ATP-funded project: the LORD Balancing System (for turning centers, high-speed grinders, and machine centers), the LORD Turbomachinery Balancing System (for turbines, compressors, pumps, generators, and motors), and the LORD Fan Balancing System (for centrifugal induced draft/forced draft and axial-vane fans). Outlook: The outlook for this real-time, high-speed machining technology is uncertain. LORD Corporation has on the market three high-quality, active, high-speed balancing systems with spindle, turbomachinery, and fan applications, but adoption by others is uncertain due to the high installation and equipment costs associated with these systems. Composite Performance Score: * * Number of Employees: 25 employees at project start, 30 as of May 2006. Focused Program: Motor Vehicle Manufacturing, 1997 Company: LORD Corporation 111 Lord Drive Cary, NC 27511-7923 Contact: Ray Misjan Phone: (919) 469-2500 Subcontractor: Professors Jun Ni and Jan Shi Manufacturing Research Center University of Michigan Ann Arbor, MI

PROJECT HIGHLIGHTS
LORD Corporation (formerly BalaDyne Corporation)

Publications: The BalaDyne/LORD real-time, high-speed balancing system gained public attention through the following publications:

· “Going Fast? Get in Balance.” Automotive Manufacturing and Production, December 1997.

· “Work Shifts Off-Center…And onto a Lathe.” Modern Machine Shop, December 1997.

· “Balancing on the Fly.” Manufacturing Engineering, March 1998.

· “Balancing on the Fly.” Cutting Tool Engineering, April 1998.

· Dyer, S.W. “Adaptive Optimal Control of Active Balancing Systems for High-Speed Rotating Machinery.” Ph.D. Dissertation, The University of Michigan, Ann Arbor, MI, 1999.

· Dyer, S.W., and E.I. Al-Regib. “Effects of Active Balancing on High-Speed Milling Precision.” Proceeding of the 14th Annual Meeting of the American Society of Precision Engineering Annual Meeting, Monterey, CA, pp. 200-203, Oct. 31-Nov. 5, 1999.

· Dyer, S.W., and J. Ni. “Adaptive Influence-Coefficient Control of Single-Plane Active Balancing Systems.” Manufacturing Science and Engineering, ASME-IMECE, MED-Vol. 10, pp. 747-755, 1999.

· Dyer, S.W., J. Ni, J. Shi, and Z.H. Zhuang. “Auto-Tuning Adaptive Supervisory Control of Active Balancing Systems.” Society of Manufacturing Engineers, May 2000.

· Dyer, S.W., and J. Ni. “Adaptive Influence-Coefficient Control of Single-Plane Active Balancing Systems.” ASME Journal of Manufacturing Science and Technology Science and Technology, Vol. 123, May 2001.

---

Research and data for Status Report 97-02-0053 were collected during January – February 2006.