The Technical Challenges of NVH
End of Line Testing
About AAM
AAM is a tier one global automotive supplier of
driveline and drivetrain systems and related
components for light trucks, SUVs, passenger cars,
crossover vehicles and commercial vehicles.
Our intense focus on engineering and
manufacturing allows us to build value for
our customers through quality, technology
leadership and operational excellence.
 ESTABLISHED: 1994
 WORLD HEADQUARTERS: DETROIT, MI
 CUSTOMERS: >100 WORLDWIDE
 LOCATIONS: >30 FACILITES IN 13 COUNTRIES
 Brazil
 China
 Germany
 India
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 Mexico
 Poland
 Scotland
 Scotland
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 Sweden
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 United States
The Technical Challenges of NVH
End of Line Testing
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Measurement Repeatability
Fundamental Design Concepts
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NVH Test Methods
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Product Characteristics
Machine Characteristic
Modal Management
Speed Sweeps
Torque Sweeps
Manufacturing Feedback Loop
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Factory Information System or FIS
Design of Experiments or DOEs
Overview
OEM customers have been requiring that axles meet or exceed certain quality requirements that
are specific to the “noise” or the energy they create under operating conditions. These products
must meet or exceed the target levels that are established by the customer. The primary
measurement machine is call a “Noise, Vibration and Harshness End of Line Test Machine”
(NVH EOLT). These machines are deployed at the end of the assembly process and perform a
NVH measurement that determines the energy level of the axle. If acceptable levels are achieved,
the axle is ready to ship to the customer, if not, the axle must be examined to
determine the issue creating a high energy condition.
Design Concepts
Measurement repeatability is achieved through using specific product datum's that
allow the product to be placed within the design tolerance of the machine’s drive
tooling. The typical range of misalignment is less than 0.250 mm.
Alignment of the product interface points to the NVH EOLT machine spindles
and are critical to a repeatable measurement system.
Design Concepts
Typical example of rear beam axle NVH EOLT datum's or location features:
Pinion elevation
datum establish
pinion nose
elevation to
input driveline
Cross car datum
establish pinion side-toside location
Carrier trunion NVH
V-pads establish tube
elevation and carrier for
aft alignment to
output absorbing
machines spindles
Design Concepts
NVH Fixture must be designed to accept the qualified surfaces of the product
and locate in the machine within 0.100 mm.
Blue circles represent where
product NVH datum's
interface with fixture.
Yellow circles represent ball
lock tooling used to located
and secure fixture to NVH
machine.
The combination of the product datum's and the fixture location in the machine ensure
the tooling is properly aligned to the product under test.
Design Concepts
The pinion drive tools and out-absorbing tools must have the flexibility to
accommodate the build variation of the product. The ability to maintain the “centers
is critical to a have a repeatable measurement system.
Pinion drive tooling
Output absorbing tooling
Flexible elements within
the tooling allow the
tooling to maintain the
center of rotation to the
product at the interface
point.
Design Concepts
NVH Fixtures contribute to the response of the axle under test. The modal content of the
fixture must be evaluated. Most fixtures will exhibit complex mode shapes. The key is to try
and mitigate the flexure modes in a frequency range of 300-600Hz.
FEA modeling is recommended.
Design Concepts
Example of the order color map for drive side speed sweep.
Fundamental hypoid
gear mesh order
Localized machine
induced resonances
Localized machine resonances can
influence accuracy of the NVH EOLT.
Test Methods
There are two types of test methods that AAM employs on its test NVH EOLT
stands. The Speed Sweep profile and the Torque Sweep profile.
Both test profiles have specific advantages.
Test profile may be specific based on OEM requirements.
Test Methods
Example of the 1st gear mesh harmonic order cut for the two different test methods:
Feed Back Loop
A FIS System is used to monitor the results of the products and review the
performance based on part type.
Model type that
has less than 98%
first time quality or
FTQ
Immediate action is required on
low performing part numbers.
Feedback Loop
Using statistical tools we can further evaluate the distribution of the current product
to target the area of improvement.
Histograms represent the NVH EOLT
results for each flank form of the gear.
Feedback Loop
Statement: 3.23 Ratio Coast Side
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NVH low FTQ performance
Gear pattern contact coast heel tendency
Project: Review Gear Design to Improve the Pattern Contact Position and NVH Performance
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Analysis of NVH rejects …identify issue..
Review Gear lapping process…verify current process. Recommend changes to lapping summary's
Trials with new lapping summary to move the pattern coast center-toe
Modify gears’ acceptance criteria at inspection (not allowing heel pattern coast)
Build and test with new gear’s, with lapping summary changes to verify a reduction in NVH response.
Review production data from NVH machine to verify lapping summary changes have corrected the low FTQ issue
BOB G. Set (Long Pattern Contact)
NVH : D -10 C -10
B. LASH: 0.217 mm
P.SHIM: .034”
WOW G. Set (Short Pattern Contact)
NVH : D -9.0 C 2.0
B. LASH: 0.197 mm
P.SHIM: .034”
Summary
The technical aspects of NVH end-of-line testing can be a challenge, but they are also
beneficial to the manufacturing process. Special care must be taken to ensure that the
product has features that allow for the acceptable alignment in the NVH EOLT
machine.
In addition, dynamic modes of the machine must be managed and understood in
order to use the data for improvements to the manufacturing process.
Finally, a strong engineering team is needed to evaluate the data that is generated by
the NVH EOLT machine to drive continuous improvement in the manufacturing
processes.
Questions?
Recognition
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AAM Associates
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Ricardo Villpondo, AAM GMC Manufacturing Engineering Area Manager
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Carlos GonzalezAyala, AAM NVH and Reliability Garage Coordinator
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Nick Derra, AAM NA Senior Manufacturing Engineer
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Mike Hunter, AAM NA Engineering analyst
Burke Porter Machinery
730 Plymouth Road NE, Grand Rapids, Mi. 49505
www.bepco.com
THANK YOU!
Cary Ketelhut
Manufacturing Engineer Manager
313-758-4129
Cary.Ketelhut@aam.com
www.aam.com