MANUFACTURING
LORD Corporation (formerly BalaDyne Corporation)
Superior, Real-Time Balancing System for
High-Speed Machining
The
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
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
· 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).
· 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 American 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.
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 precisionturning. 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.
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
Conclusion
From
October 1997 to September 2000, BalaDyne Corporation, in partnership with the
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
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
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.
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 at project start, 30 as
of May 2006.
Focused
Program: Motor Vehicle Manufacturing,
1997
Company:
LORD Corporation
Contact:
Ray Misjan
Phone: (919) 469-2500
Subcontractor:
Professors Jun Ni and Jan Shi
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
·
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.